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| David Brown <david.brown@hesbynett.no>: Oct 27 01:36AM +0200 On 26/10/16 23:55, Jerry Stuckle wrote: >> Those are not emulations. (I know I am flogging a dead horse here.) > I can run QEMU on my system here and load and execute code for a Cortex > A-9 processor. So according to you I have an ARM processor on my laptop. Eh, no. The hint is in the name. RAID is not a type of device or hardware, it is a way of organising data. Whether you do it with dedicated hardware or pure software is irrelevant. > Exactly. You don't need to change it, so your argument is as full of > crap as you are. However, I know you need to use RAID emulation because > you can't select the appropriate RAID device in the first place. I said one of the key features of software raid, compared to hardware raid, is its flexibility and its options. I didn't say you would be likely to change these options in an existing system - it is possible, and occasionally useful, but not common. >> I hope you aren't trying to say that /only/ small users use Linux! > I never said anything of the sort. Your logic is as fallacious as the > rest of your arguments. Read what I wrote - "I /hope/ you aren't trying to say...". Your writing was unclear - and now you have confirmed what you were /not/ saying. Now, what /were/ you saying when you wrote "and small users sometimes use Linux" ? Was it just another empty statement? >> gmirror, or ZFS or (on a few types) btrfs. > Sure. But the code is in flash or other ROM, and not mixed in with user > code - as I said. A huge difference. They may typically store some or all of their software in flash (not ROM!), but it is a sizeable NAND flash with a filesystem. There is no difference between a flash filesystem and a filesystem on a disk - it is the same software, and works in the same way. It may be restricted to make it difficult to run other programs on the system (though often there is a ssh daemon for more advanced users), and certainly you would normally not choose to run programs that are not associated with the NAS functionality. But that is just like any other server - if you want the server to be efficient and reliable, you use it for the functions and programs that are needed for that server, and not for other purposes. The difference is minor at most. >> know what is going on under the bonnet. > No, you haven't designed anything, have you, David. But you are an > expert on EVERYTHING! ROFLMAO! It should not really be a surprise that a person can understand how something works without having designed the thing in practice. After all, surely someone who /has/ designed a hardware RAID card had a fair idea how it should work before starting the design? I bet even you have a fair idea how a normal car engine works - but I also bet you have never designed one. It just happens that with RAID, I find the theory fascinating even though I have little need for complicated RAID setups in practice. I enjoy the mathematics involved in multi-parity raid. It is weird to do maths for fun, I know, but there we have it. >> or unusual device. > Gee, that would be exactly the same thing you would do if your RAID > controller died. No, if your raid controller card died you would need to get a replacement raid controller card of the same (or very similar) type. That is not the same thing as getting another computer. > And it's not so easy to just boot an OS for an old or > unusual computer on a new one. So once again your argument is full of crap. Why would you use an old or unusual computer? Why would you use an unusual OS? One of the points about using software raid is that it works on bog-standard computers. Unless you are talking about pre-SATA disk interfaces, you just take the disk out the old computer and attach it to the new one. You either install the same version of Linux (or BSD, or FreeBSD, or whatever) that you had on the old system, or you install a newer version if you want. It will still work fine with the disks. >> a client. Assuming it has the right permissions, your raid system will >> do what it is designed to do - store the damaged file on the disks. > Again you have no idea. Viruses can be spread throughout the system. Security and reliability is never absolute - it is all a matter of reducing likelihoods of problems, and consequences of problems. Yes, you /can/ get viruses or malware on your servers. But if your servers are managed reasonably well your chances of getting a virus in them are extremely small. With a Linux server with few services other than file sharing (NFS, Samba), decent passwords and sensible filesystem permissions, and a firewall protecting it from the most dangerous outside forces, then you will not expect to have any serious risk of malware infections within the working lifetime of the server. That does not mean that it cannot happen - it means it is highly unlikely. > But the viruses cannot destroy the partitioning, directories, etc. disk > on a RAID device. It can corrupt data, but only data allowed by file > permissions. Have you ever actually /used/ any sort of raid system? I mean, have you ever configured a raid system and installed an OS on a PC that uses raid? If you had, you would realise that a raid set appears to the OS as one big virtual disk. (This is for hardware raid, or normal software raid. Raid built into a filesystem is a little different.) On that virtual disk, you make your partitions, build your filesystems, and install your OS and data. To the OS, and to any programs running on it - including a virus - there is no logical difference between a filesystem on a hardware raid set or a filesystem on a software raid set or a filesystem on a plain disk. If the virus is running with permissions to do "rm -rf /", it has the same effect with or without raid. If the virus has permission to run "parted" or access the raw device files, it can screw with the partitioning. If it can access the software used for configuring the hardware raid sets, it could even screw with them (it is highly unlikely that it would bother, of course - it's easy enough to destroy the data with a total disregard for any underlying raid). >> undamaged version of the file from my hourly snapshots. For older >> (pre-btrfs) systems, my snapshots are nightly. > You can do the same on RAID, if you wish. You can do it if you have a filesystem or volume manager that supports fast snapshots, or do it slowly without such support. > Sure - but only the files my current ID has access to. It cannot, for > instance, destroy the backups because this ID does not have permission > to access those backups. And that is the same no matter what sort of raid, or lack thereof, you might have. But you only have backups if you realise that your hardware raid card is not a backup solution as you have repeatedly claimed. |
| Ian Collins <ian-news@hotmail.com>: Oct 27 12:48PM +1300 On 10/27/16 11:08 AM, Jerry Stuckle wrote: >> Are you really trying to claim that RAID is about backup? > I'm claiming that the major use of RAID around the world is for reliable > data backup. The major use of RAID around the world is for reliable data storage. >> more slowly) even if you have a disk failure. That is what the R for >> /redundancy/ means. > Yes, which is a form of backup. Nope. That's a common mistake naive admins make until their machine goes pop or their RAID card shits its self. >> if you simply need to refer to older versions for some reason. > Two copies of a file IS backup. Even copying a file to a different > directory is a well-known method of backing up the file. Nope, its redundancy. >> replication of data. > Yes, and what do you think "continuous off-site replication of data" is, > if it's not off-site backup. Redundancy. >>> have any facts. >> Ian mentioned Oracle's cloud storage - I said how I interpreted that >> reference. How you correctly interpreted that reference. > Sure, they use RAID. And as I said earlier, RAID uses software. But > these devices are dedicated to backups - no user code is running on > them. A huge difference. Indeed, they are not dedicated to backups, they are dedicated to redundancy. -- Ian |
| David Brown <david.brown@hesbynett.no>: Oct 27 01:58AM +0200 On 27/10/16 00:08, Jerry Stuckle wrote: >> more slowly) even if you have a disk failure. That is what the R for >> /redundancy/ means. > Yes, which is a form of backup. OK, so you /are/ using the wrong words. You are making up your own terms, just like your "true raid" and "emulated raid" terms. For future reference, if you want to communicate with people about technical issues, it makes sense to use the standard terms. You might like to start by googling for "backup" and "raid" - or perhaps go straight to Wikipedia. >> if you simply need to refer to older versions for some reason. > Two copies of a file IS backup. Even copying a file to a different > directory is a well-known method of backing up the file. To be a backup, you need two /logical/ copies of a file. Two physical copies of the data block is redundancy, not a backup. A COW logical copy (such as you get with LVM, BTRFS or ZFS snapshots) is a backup (without redundancy) even though there is only one physical copy of the data - you can view them as independent files, change one while having the old backup copy remain safe, etc. Copying a file to a different directory is a simple backup, yes. >> replication of data. > Yes, and what do you think "continuous off-site replication of data" is, > if it's not off-site backup. It is not a backup, because it is not logically independent. Any changes you make to the on-site copy are quickly (depending on network speed) copied to the off-site copy. If normal usage changes your copies, they are not backups! Also note that this sort of continuous off-site replication is not a common usage, and it is certainly not supported by any hardware raid system. >> data is needed in an application - the data has to pass through the cpu >> anyway. > Your proof? You don't have it, because once again you are full of crap. Do your own research. It should not take long to google. > Even with two disks you are halving the amount of data going through the > CPU. And it is much more than just the data. It includes commands to > two (or more) drives, additional wait times for seeks, etc. So what? Double a small amount is still a small amount. On my servers I see a few percent cpu time used for the raid1 sets. Even with raid6, the cpu time is generally irrelevant. With a half-decent cpu, it is faster to use transparent compression on your filesystems - even with the cpu time needed for compression and decompression, the throughput is faster than reading straight from a hard disk. And compression and decompression is a good deal more cpu intensive than even raid6. > Current controllers use processors just as fast as modern computers. In > fact, some are faster because they can use RISC processors and code > optimized to those processors. No, they are not faster. And they have significant latencies compared to direct host access of SSD's. >> The processor has more than enough cycles to spare. And if it doesn't, >> it is more cost-effective to buy more or faster cpus. > Of course it does, when all you use it for is to play FreeCell. Maybe you play Freecell on your servers, but most of us do not. >> reference. > And "may have meant"? Based on what facts? At least you admitted you > don't have any facts - just an opinion. I never claimed to have facts here - just my interpretation. And I am sure Ian will let me know if I guessed incorrectly. > Sure, they use RAID. And as I said earlier, RAID uses software. But > these devices are dedicated to backups - no user code is running on > them. A huge difference. In what possible way is it different? You run appropriate server systems on your servers - you don't let any user log in and run whatever "user code" they fancy. If your machine is primarily a file server, then you run file serving services on it. If it is some sort of application server, then you run those services on it. And if you really have services that demand maximal cpu time, then you are likely to want the fastest raid types - raid1 and raid10, which have completely negligible cpu costs. |
| Jerry Stuckle <jstucklex@attglobal.net>: Oct 26 10:27PM -0400 On 10/26/2016 6:52 PM, Ian Collins wrote: > No, QEMU *is* an emulator. > "QEMU is a generic and open source machine emulator and virtualizer." > http://wiki.qemu.org/Main_Page So is RAID emulation. No difference. >> Sure. But the code is in flash or other ROM, and not mixed in with user >> code - as I said. A huge difference. > Ah, so now you agree that software RAID is RAID. Good start. No, software RAID is a RAID emulator. Just like QEMU is an emulator. >> There are many instances, especially recently, of entire networks being >> infected - including servers. > Reference (assuming you aren't referring to Windows servers)? Have you read the news lately? Nope, because I know you can't read. >> on a RAID device. It can corrupt data, but only data allowed by file >> permissions. > A rootkit can destroy everything. Not if it isn't executed. But you wouldn't know that, either. -- ================== Remove the "x" from my email address Jerry Stuckle jstucklex@attglobal.net ================== |
| Ian Collins <ian-news@hotmail.com>: Oct 27 03:43PM +1300 On 10/27/16 03:27 PM, Jerry Stuckle wrote: >> "QEMU is a generic and open source machine emulator and virtualizer." >> http://wiki.qemu.org/Main_Page > So is RAID emulation. No difference. I guess the real world and Jerry world will have to disagree on that one. To confuse you further: ZFS can emulate Redundant Array of Independent Disks by using disk files as emulated disks. -- Ian |
| Jerry Stuckle <jstucklex@attglobal.net>: Oct 26 10:48PM -0400 On 10/26/2016 7:36 PM, David Brown wrote: > RAID is not a type of device or hardware, it is a way of organising > data. Whether you do it with dedicated hardware or pure software is > irrelevant. Only an incompetent idiot like you would even try to claim that software RAID is the same as hardware RAID. > raid, is its flexibility and its options. I didn't say you would be > likely to change these options in an existing system - it is possible, > and occasionally useful, but not common. And it's ability to corrupt the entire array due to a virus. But a COMPETENT person wouldn't even consider the need to change these options, because he or she would make the right decision in the first place. Just another straw man argument by an incompetent troll. > Read what I wrote - "I /hope/ you aren't trying to say...". Your > writing was unclear - and now you have confirmed what you were /not/ > saying. My writing was perfectly clear. I can't help it if your lack of understanding of computers and the English language doesn't allow you to understand it. But that's just like an incompetent troll. > Now, what /were/ you saying when you wrote "and small users sometimes > use Linux" ? Was it just another empty statement? Exactly what I said. Nothing more, nothing less. But I know you try to put words into my mouth. It doesn't work, troll. > functionality. But that is just like any other server - if you want the > server to be efficient and reliable, you use it for the functions and > programs that are needed for that server, and not for other purposes. First of all, it can be in ROM, also. There are still systems out there with their code in ROM - typically high security systems where the software *must* not be changed. But you've never worked on any critical systems - or even moderately secure systems, so you have no idea. And no, these servers are designed so that other software *cannot* run on them and potentially corrupt the disks. Not that you would understand the concept - it's way past your level of intelligence. > idea how it should work before starting the design? I bet even you have > a fair idea how a normal car engine works - but I also bet you have > never designed one. You can't even understand how something works, as you have repeatedly proven. And no, as any hardware designer will tell you - you can't really understand how something works until you have designed it. And only you would consider a car engine to be similar to a RAID device. Just more proof you don't understand RAID. > though I have little need for complicated RAID setups in practice. I > enjoy the mathematics involved in multi-parity raid. It is weird to do > maths for fun, I know, but there we have it. You can find the theory as interesting as you like. But you don't understand even the basics of a RAID system - only how to use one. And even that understanding is demonstratably limited. > No, if your raid controller card died you would need to get a > replacement raid controller card of the same (or very similar) type. > That is not the same thing as getting another computer. Or you just get another RAID device and move your disks to that device. No problem. > BSD, or FreeBSD, or whatever) that you had on the old system, or you > install a newer version if you want. It will still work fine with the > disks. For the same reason you are using an old or unusual RAID device. I'm comparing apples to apples. But I know you can't do that, because it destroys your arguments. And the old version of Linux may no longer be available, and new versions may not run on the old device. Just like an old controller card may not be available and a new controller card may not work in the RAID device. > outside forces, then you will not expect to have any serious risk of > malware infections within the working lifetime of the server. That does > not mean that it cannot happen - it means it is highly unlikely. Not in any of your systems, it isn't. But a properly designed RAID device is immune to such problems because other code *never* runs on the RAID device. >> permissions. > Have you ever actually /used/ any sort of raid system? I mean, have you > ever configured a raid system and installed an OS on a PC that uses raid? I've been using RAID since the 80's. But I've never installed an OS on a PC that uses RAID. They are too insecure. > configuring the hardware raid sets, it could even screw with them (it is > highly unlikely that it would bother, of course - it's easy enough to > destroy the data with a total disregard for any underlying raid). I know how it appears. And I know that some file systems have RAID emulation built into them. But you once again show your lack of knowledge when you claim that a hardware RAID will execute a virus. It can't, because there is no way for any external code to be executed on the RAID device. It can't run partd. or anything else. A virus on a user computer can corrupt individual files the user has permission to write. But there is no way it can corrupt other files or the disks, as can happen with software emulation. And you claim that RAID emulation can be done on multiple virtual partitions on a disk. But that violates your earlier statement that one of the advantages of RAID is to be speed up access by spreading the data over multiple physical disks. Which is it? Oh, I forgot. It's whatever argument is convenient for you at the time. You change your tune more often than some people change their shorts. But that's what a troll does. >> You can do the same on RAID, if you wish. > You can do it if you have a filesystem or volume manager that supports > fast snapshots, or do it slowly without such support. Sure. And you can fly to the moon if you have a big enough rocket. But RAID can do it automatically, with no speed reduction. > might have. > But you only have backups if you realise that your hardware raid card is > not a backup solution as you have repeatedly claimed. Nope, if you have RAID emulation a virus can corrupt the entire disk. But the hardware RAID card can easily be a backup solution. The most obvious way is by configuring it for RAID 1. But once again you show your ignorance by your statements. Give it up, David. The hole you're digging just keeps getting deeper. -- ================== Remove the "x" from my email address Jerry Stuckle jstucklex@attglobal.net ================== |
| Jerry Stuckle <jstucklex@attglobal.net>: Oct 26 10:50PM -0400 On 10/26/2016 6:34 PM, Ian Collins wrote: >> No one ever said it was. However, you have to try to put words into >> other peoples' mouths to try to make a point. > You keep conflating the terms. Nope. You just keep trying to put words in other peoples' mouths to try to support your idiotic claims. >>> "people who need high reliability" or big companies? >> You don't know the difference there, either. > Difference between what? I rest my case. >> Yes, and the big companies who use real RAID devices for their critical >> reliability systems. > Oracle engineered systems all use ZFS. Oh yes? You know every Oracle system? Quite a grand statement from someone who just a couple of days ago admitted he knew very little about RAID - but now you're an expert in everything RAID - including every product Oracle has. Want to try again, troll? -- ================== Remove the "x" from my email address Jerry Stuckle jstucklex@attglobal.net ================== |
| Jerry Stuckle <jstucklex@attglobal.net>: Oct 26 10:55PM -0400 On 10/26/2016 7:48 PM, Ian Collins wrote: >> I'm claiming that the major use of RAID around the world is for reliable >> data backup. > The major use of RAID around the world is for reliable data storage. So that is different from your previous claim that the major use is for fast access? Which is it? And reliable data storage requires data backup. >> Yes, which is a form of backup. > Nope. That's a common mistake naive admins make until their machine > goes pop or their RAID card shits its self. No, it is a common mistake people like YOU make that a backup is only manual, only happens on occasion, and can be out of date. High reliability systems run constant backups using RAID and can switch to the backup at any time with no loss of data. But you wouldn't know what a low reliability system is - much less high reliability, as you have repeatedly demonstrated. >> Two copies of a file IS backup. Even copying a file to a different >> directory is a well-known method of backing up the file. > Nope, its redundancy. It is also backup. See above. >> Yes, and what do you think "continuous off-site replication of data" is, >> if it's not off-site backup. > Redundancy. See above. >> them. A huge difference. > Indeed, they are not dedicated to backups, they are dedicated to > redundancy. What you call redundancy is just another form of backup. Not that you would understand the concept, because you have never worked on a system requiring high reliability. -- ================== Remove the "x" from my email address Jerry Stuckle jstucklex@attglobal.net ================== |
| Ian Collins <ian-news@hotmail.com>: Oct 27 03:57PM +1300 On 10/27/16 03:48 PM, Jerry Stuckle wrote: >> irrelevant. > Only an incompetent idiot like you would even try to claim that software > RAID is the same as hardware RAID. Which is why David didn't. >> That is not the same thing as getting another computer. > Or you just get another RAID device and move your disks to that device. > No problem. A Redundant Array of Independent Disks device, that's a new one. >> ever configured a raid system and installed an OS on a PC that uses raid? > I've been using RAID since the 80's. But I've never installed an OS on > a PC that uses RAID. They are too insecure. By the way you describe things, you stopped using RAID in the 80s as well. There's me thinking Jerry world was stuck in the 90s. -- Ian |
| Ian Collins <ian-news@hotmail.com>: Oct 27 04:00PM +1300 On 10/27/16 03:50 PM, Jerry Stuckle wrote: > On 10/26/2016 6:34 PM, Ian Collins wrote: >> Oracle engineered systems all use ZFS. > Oh yes? You know every Oracle system? I work with Oracle storage. -- Ian |
| Ian Collins <ian-news@hotmail.com>: Oct 27 04:07PM +1300 On 10/27/16 03:55 PM, Jerry Stuckle wrote: >> The major use of RAID around the world is for reliable data storage. > So that is different from your previous claim that the major use is for > fast access? I made no such claim. > And reliable data storage requires data backup. Indeed. The two are not the same. -- Ian |
| Jerry Stuckle <jstucklex@attglobal.net>: Oct 26 11:13PM -0400 On 10/26/2016 7:58 PM, David Brown wrote: >> Yes, which is a form of backup. > OK, so you /are/ using the wrong words. You are making up your own > terms, just like your "true raid" and "emulated raid" terms. Nope. RAID devices such as RAID 1 keep identical copies of files on different disks. These are backups. > technical issues, it makes sense to use the standard terms. You might > like to start by googling for "backup" and "raid" - or perhaps go > straight to Wikipedia. Yes, and you should understand backup. But then there are facts, and there is Wikipedia. Sometimes the two mesh - but not often. And obviously you get your information from Wikipedia. > data - you can view them as independent files, change one while having > the old backup copy remain safe, etc. > Copying a file to a different directory is a simple backup, yes. Wrong answer. Redundancy is a live backup. It follows all changes to the original file. And just because you can't access it directly on a RAID device does not mean it is not a backup. > changes you make to the on-site copy are quickly (depending on network > speed) copied to the off-site copy. If normal usage changes your > copies, they are not backups! Backups don't need to be logically independent. They need to be physically independent, which RAID 1 creates. And it can be logically separated by removing one disk and placing it in another device. > Also note that this sort of continuous off-site replication is not a > common usage, and it is certainly not supported by any hardware raid > system. I never said it was. YOU are the one who brought up cloud storage, not me. But you forgot that point also, didn't you? >>> anyway. >> Your proof? You don't have it, because once again you are full of crap. > Do your own research. It should not take long to google. I have. The difference is I have used hardware RAID controllers - unlike you. Of course, the other difference is I use my computers for more than playing FreeCell. Once again, you made a statement without proof - and you can't back it up because you have admitted you have ZERO experience with hardware RAID. But you are an expert on it! ROFLMAO! > the cpu time needed for compression and decompression, the throughput is > faster than reading straight from a hard disk. And compression and > decompression is a good deal more cpu intensive than even raid6. Of course that's all you see. But then it doesn't take a lot of CPU to play FreeCell. But on a decently active system, software RAID emulation will definitely slow it down. >> optimized to those processors. > No, they are not faster. And they have significant latencies compared > to direct host access of SSD's. ROFLMAO! Once again you admit you have never used a RAID controller. But once again you're trying to compare apples and oranges. How about comparing apples and apples - hard disks on a computer vs. hard disks on a RAID device. Or SSD's on a computer vs. SSD's on a RAID device. In all cases a good RAID device will outperform RAID emulation, especially on a heavily used system. >>> it is more cost-effective to buy more or faster cpus. >> Of course it does, when all you use it for is to play FreeCell. > Maybe you play Freecell on your servers, but most of us do not. No, I guess that is beyond your level of competency. >> don't have any facts - just an opinion. > I never claimed to have facts here - just my interpretation. And I am > sure Ian will let me know if I guessed incorrectly. You sure talk like what you say are facts. And I wouldn't count on Ian to verify anything - he's already admitted he knows little about RAID devices. But suddenly he's an expert. Just the blind leading the blind. > really have services that demand maximal cpu time, then you are likely > to want the fastest raid types - raid1 and raid10, which have completely > negligible cpu costs. The difference is the RAID devices do not (and in fact cannot) run user code. There is no way to corrupt the disk or data unrelated to the user currently accessing the disk. And the CPU time required can be critical in a system that does more than play FreeCell (not that even that is up to your level of competency). -- ================== Remove the "x" from my email address Jerry Stuckle jstucklex@attglobal.net ================== |
| Jerry Stuckle <jstucklex@attglobal.net>: Oct 26 11:16PM -0400 On 10/26/2016 2:54 PM, Ian Collins wrote: >> ROMs). > It is what everyone in the storage business calls them: EMC, your > beloved IBM, Oracle, the list goes on. According to someone who just a couple of days ago admitted he knew very little about RAID - but now you know how "everyone in the storage business" calls them? ROFLMAO! >> are wrong. And you would NEVER do that. > If he agreed with your made up definitions he would be a fool, which he > isn't. No, calling you a fool would be an insult to real fools. >> It is, however, how the industry defines RAID and RAID emulation. > Which industry would that be, horticulture? Even Google can't find a > relevant definition. No, I can believe *you* couldn't find a definition - relevant or not. But so much for someone who just a couple of days ago admitted he knew very little about RAID - but now you're an expert? ROFLMAO! -- ================== Remove the "x" from my email address Jerry Stuckle jstucklex@attglobal.net ================== |
| Jerry Stuckle <jstucklex@attglobal.net>: Oct 26 11:22PM -0400 On 10/26/2016 2:27 PM, Chris Vine wrote: > I am glad that you appear to have understood it ... except that it also > appears below that you didn't. Stick to this one and you are doing > fine. Oh, I understand it perfectly. > with a given resistance, and (b) if there is no reactance in the circuit > (capacitive or inductive) - in other words, that the system is in a > steady state. That is correct. Ohms law is one of the basic laws of physics. Voltage is the difference in charges between two points. But if you have an infinite resistance, you can have no charge difference because there is no relationship between the points. > No. It is a source of EMF measured in volts (this time really by > definition). It *may* cause a current to flow in a circuit and so do > work, and will do so if a conducting medium is connected to it. Once again, false. A single electrode on a battery has no voltage. Only when you have a connection between the anode and the cathode can you have a difference in voltage. And that difference causes a current to flow. > The pressure in your water supply pipe does not go to zero when you > turn your tap off. The pressure is there all the time, courtesy of your > supply company. Only because on the other side of the tap you have a lower pressure. You have a connection between the two. But once again you can only measure that difference by measuring the difference between pressure in the water line and pressure external to the water line. >> connected. It is an extreme example to show the fallacy of your >> logic. > It shows no such thing. Then you can prove how connecting a voltmeter to just one electrode and placing the other electrode on the moon will show a voltage. It should be simple. -- ================== Remove the "x" from my email address Jerry Stuckle jstucklex@attglobal.net ================== |
| Ian Collins <ian-news@hotmail.com>: Oct 27 04:25PM +1300 On 10/27/16 04:16 PM, Jerry Stuckle wrote: > According to someone who just a couple of days ago admitted he knew very > little about RAID - but now you know how "everyone in the storage > business" calls them? Where did I say I know very little about RAID? Come on, show the quote and prove me wrong. I've been in the storage business for a very long time. -- Ian |
| Jerry Stuckle <jstucklex@attglobal.net>: Oct 26 11:27PM -0400 On 10/26/2016 12:45 PM, Christian Gollwitzer wrote: > between one of it's connectors and an infinitely distant point? The > answer is U/2, half of the battery voltage. > Christian Christian, Yes and now. Phi is a theoretical voltage, quite useful for modeling ideal systems. But in real life, systems are never ideal, and to measure that potential difference upsets the theoretical model. Just like modeling a battery in electrodynamics assumes an internal resistance of 0 ohms, which is never the case in real life. But it simplifies the modeling, and is often small enough that it can be ignored in most situations. -- ================== Remove the "x" from my email address Jerry Stuckle jstucklex@attglobal.net ================== |
| Jerry Stuckle <jstucklex@attglobal.net>: Oct 26 11:29PM -0400 On 10/26/2016 5:57 PM, David Brown wrote: > Is it not 1/r² drop-off from a point charge? Or would that be the > drop-off of the electric field, and the potential is the integral of > that (in which case I understand the 1/r factor)? From a point source, it is 1/r². From a surface, it is 1/r. But then you should know that - after all, you're an expert in everything. >> Christian > I suppose the potential phi of an object is the energy it takes to move > one Coulomb of charge from an infinite distance to the neutral object? There is no such thing as a "neutral object". And it would take an infinite amount of energy to move anything, including a charge, an infinite distance. -- ================== Remove the "x" from my email address Jerry Stuckle jstucklex@attglobal.net ================== |
| Jerry Stuckle <jstucklex@attglobal.net>: Oct 26 11:31PM -0400 On 10/26/2016 4:20 PM, Ben Bacarisse wrote: >> Yes - but it is only the ability to generate power. > What is the alternative name for joules per coulomb? > <snip> It is the volt. But it is still only the ability to generate power (work, actually). Coulomb is a relative measurement, not an absolute. -- ================== Remove the "x" from my email address Jerry Stuckle jstucklex@attglobal.net ================== |
| Christian Gollwitzer <auriocus@gmx.de>: Oct 27 08:55AM +0200 Am 27.10.16 um 05:13 schrieb Jerry Stuckle: > I have. The difference is I have used hardware RAID controllers - > unlike you. Of course, the other difference is I use my computers for > more than playing FreeCell. It seems you use it mainly to write excessive Usenet posts. Incidentally, the game you continue to refer to is from the early 90s. I think you should patent the time machine you are using. Christian |
| Christian Gollwitzer <auriocus@gmx.de>: Oct 27 09:04AM +0200 Am 27.10.16 um 05:22 schrieb Jerry Stuckle: > That is correct. Ohms law is one of the basic laws of physics. Not really. It is an assumed material characteristics, the same as Hooke's "Law". If you stretch a spring too much, the force will no longer be linearly proportional to the displacement. The same with current in a conducting medium. But admittedly, for a large practical range, you can forget about nonlinearities and assume Ohm's Law is correct. For many other practical applications, it isn't. A diode (or LED) does NOT obey Ohm's "law". > Voltage > is the difference in charges between two points. Nope, difference between potential. Charge and potential are related by Maxwell's equations, a set of partial differential equations. > But if you have an > infinite resistance, you can have no charge difference because there is > no relationship between the points. Jerry's lecture notes on physics. Nice. Christian |
| Christian Gollwitzer <auriocus@gmx.de>: Oct 27 09:44AM +0200 Am 26.10.16 um 23:57 schrieb David Brown: > Is it not 1/r² drop-off from a point charge? Or would that be the > drop-off of the electric field, and the potential is the integral of > that (in which case I understand the 1/r factor)? Yes, exactly. For a single isolated static point charge at the origin, the potential is phi(r) = q/(4*pi*epsilon0) *1/r. The electric field is the gradient of this potential E=-grad phi = q/(4pi*epislon0) * 1/r^2 *r^, where r^ is a unit vector pointing from the origin. A battery can be considered an electric dipole, for which indeed the potential drops off at a higher rate, phi~1/r^2 and E~1/r^3. See https://en.wikipedia.org/wiki/Electric_dipole_moment for plots and formulae. > I suppose the potential phi of an object is the energy it takes to move > one Coulomb of charge from an infinite distance to the neutral object? Yes, the potential is usually defined in this way that at infinity it is zero (because for a finite amount of charges, it always drops off), but in general it is defined only up to constant. The energy difference in moving a test charge q from x1 to x2 is q*(phi(x2)-phi(x1)). The endpoint can be anywhere in space, not necessarily on the surface of the object. Christian |
| Chris Vine <chris@cvine--nospam--.freeserve.co.uk>: Oct 27 10:14AM +0100 On Wed, 26 Oct 2016 23:22:46 -0400 Jerry Stuckle <jstucklex@attglobal.net> wrote: [snip] > Voltage is the difference in charges between two points. But if you > have an infinite resistance, you can have no charge difference > because there is no relationship between the points. You are clueless. |
| David Brown <david.brown@hesbynett.no>: Oct 27 12:08PM +0200 On 27/10/16 04:43, Ian Collins wrote: > I guess the real world and Jerry world will have to disagree on that one. > To confuse you further: ZFS can emulate Redundant Array of Independent > Disks by using disk files as emulated disks. I don't know about ZFS, but just for laughs I have done this with Linux md raid where the files that are stored on a tmpfs filesystem, which is normally in memory, except when bits of it the files get swapped out (and with swap partitions on two disks, these also effectively form a raid-0 pair). Clearly you don't store your files in such arrangements, but they are excellent for practising with the tools and familiarising yourself with failure recovery, resizing/reshaping, etc. |
| Juha Nieminen <nospam@thanks.invalid>: Oct 27 06:19AM > You do not know me, Daniel. You > cannot make that assessment. We know you quite well. You are a dishonest self-righteous hypocrite who thinks that his magical incantations will influence people over the internet. --- news://freenews.netfront.net/ - complaints: news@netfront.net --- |
| Juha Nieminen <nospam@thanks.invalid>: Oct 27 06:17AM > Depends perhaps for what you need it but someone may be has already > made some C++ classes for manipulating PNG files and published these. > For example that library looks like one: http://freeimage.sourceforge.net/ If I'm developing a libpng wrapper, I'm not going to use someone else's wrapper. --- news://freenews.netfront.net/ - complaints: news@netfront.net --- |
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