axeman Posted December 27, 2013 Share Posted December 27, 2013 I am currently pre-clearing a good number of drives (2 done, 1 at 90% and another to be started in the next day or so) on a test UnRaid install . They are in a temp setup at the moment. I want to get some benchmarks/speedtests run on it. After that, I need to get these drives added to my production array. How do I do this? If I add them to my prod array, will i be able to reformat? or will Unraid just mount the disk, and show me contents (and rebuild array)? Link to comment
dgaschk Posted December 28, 2013 Share Posted December 28, 2013 If they are pre-cleared they can be added to the array quickly. If the disks are being added and not used as replacement drives then option to format will appear after they are added. The disks have been cleared so they have no contents. If the disks are used to replace a current drive then there will be no option to format because formatting is included when the partition is rebuilt. When replacing a drive the contents should be available continuously. Link to comment
axeman Posted December 28, 2013 Author Share Posted December 28, 2013 If they are pre-cleared they can be added to the array quickly. If the disks are being added and not used as replacement drives then option to format will appear after they are added. The disks have been cleared so they have no contents. If the disks are used to replace a current drive then there will be no option to format because formatting is included when the partition is rebuilt. When replacing a drive the contents should be available continuously. thanks for the reply - but after pre-clearing, i'm going to throw them in a temp/test setup. and put some files on there. after my testing, i want to remove these drives and add them to my other array. so even though the drive has been formatted after the pre-clear, adding it to another array will let me reformat? that would be ideal :-) Link to comment
garycase Posted December 28, 2013 Share Posted December 28, 2013 After you've added data to the drive, it will need to be cleared again to add it to your array. UnRAID will do this; or you can simply run another pre-clear run. Since I assume at that point you will already be confident in the drive, you can do just the pre-clear operation itself, skipping the pre- and post- reads, so it will be MUCH quicker (about 1/4th the normal time). Just use the -n option with the preclear. Link to comment
axeman Posted December 28, 2013 Author Share Posted December 28, 2013 After you've added data to the drive, it will need to be cleared again to add it to your array. UnRAID will do this; or you can simply run another pre-clear run. Since I assume at that point you will already be confident in the drive, you can do just the pre-clear operation itself, skipping the pre- and post- reads, so it will be MUCH quicker (about 1/4th the normal time). Just use the -n option with the preclear. thanks - that sounds like a plan - i was DREADING having to run pre-clear on these drives, AGAIN. on a 4TB drive, it takes a very very very long time (great for stress testing the hell out of the drive while driving my patience into the ground). Link to comment
Joe L. Posted December 29, 2013 Share Posted December 29, 2013 After you've added data to the drive, it will need to be cleared again to add it to your array. UnRAID will do this; or you can simply run another pre-clear run. Since I assume at that point you will already be confident in the drive, you can do just the pre-clear operation itself, skipping the pre- and post- reads, so it will be MUCH quicker (about 1/4th the normal time). Just use the -n option with the preclear. thanks - that sounds like a plan - i was DREADING having to run pre-clear on these drives, AGAIN. on a 4TB drive, it takes a very very very long time (great for stress testing the hell out of the drive while driving my patience into the ground). Almost any writing to a precleared drive would either invalidate its preclear signature OR give you a false sense that parity is correct after adding the drive to the array, when in reality, it is not. Best bet is to test with files first, then to run the preclear. Joe L. Link to comment
garycase Posted December 29, 2013 Share Posted December 29, 2013 As Joe noted, you do not want to write to the disk after you do another preclear. I assume that's obvious ... and that after you do the preclear -n I noted above you plan to directly add it to your array; but it doesn't hurt to emphasize that if you then wrote anything else to the disk you'd have to do it again Link to comment
axeman Posted December 29, 2013 Author Share Posted December 29, 2013 After you've added data to the drive, it will need to be cleared again to add it to your array. UnRAID will do this; or you can simply run another pre-clear run. Since I assume at that point you will already be confident in the drive, you can do just the pre-clear operation itself, skipping the pre- and post- reads, so it will be MUCH quicker (about 1/4th the normal time). Just use the -n option with the preclear. thanks - that sounds like a plan - i was DREADING having to run pre-clear on these drives, AGAIN. on a 4TB drive, it takes a very very very long time (great for stress testing the hell out of the drive while driving my patience into the ground). Almost any writing to a precleared drive would either invalidate its preclear signature OR give you a false sense that parity is correct after adding the drive to the array, when in reality, it is not. Best bet is to test with files first, then to run the preclear. Joe L. thanks Joe - i'm pretty much done with testing, do I need to run a FULL pre-clear? or as gary stated, will the -n option put me back into actually pre-cleared status again? Link to comment
garycase Posted December 29, 2013 Share Posted December 29, 2013 As I noted above, the -n option pre-clears the disk. It simply skips the pre-read and post-read steps, which together take about 75% of the time for a full cycle ... so the preclear will finish in about 1/4th the time of a full cycle. Link to comment
axeman Posted December 29, 2013 Author Share Posted December 29, 2013 As I noted above, the -n option pre-clears the disk. It simply skips the pre-read and post-read steps, which together take about 75% of the time for a full cycle ... so the preclear will finish in about 1/4th the time of a full cycle. thanks Gary! Link to comment
axeman Posted February 14, 2014 Author Share Posted February 14, 2014 hello - waking this thread up again... so some time passed... and i just added the 4TB to my production array. i'm pretty sure i ran a pre-clear with the -n option way back when after testing... but it's been so long, that I don't remember. Upgrading the parity drive causes a full sync, right? does that mean i'm safe and protected, or if i skipped pre-clearing after testing, am i potentially at risk? Should I stop the array and re-preclear the parity drive with the -n option? as always - guidance is appreciated. Link to comment
trurl Posted February 14, 2014 Share Posted February 14, 2014 Upgrading parity will sync (rebuild) the parity drive. Doesn't matter whether precleared or not. You are not protected until parity is valid again. Link to comment
jumperalex Posted February 14, 2014 Share Posted February 14, 2014 You are sort of protected. That is to say if you have a data drive fail in the middle of the parity build on the new parity drive, you can stop it all, shut down, reinstall the OLD parity drive, [possible config step], and you are good to go just as if you hadn't messed with parity at all. At that point of course you'd want to get your array back up to snuff by swapping in a good data-drive, and rebuild the array. THEN ... you could try to once again upgrade your parity drive to 4TB. Link to comment
trurl Posted February 14, 2014 Share Posted February 14, 2014 As long as you don't write to the array during the parity rebuild, then the old parity would be valid. Link to comment
garycase Posted February 14, 2014 Share Posted February 14, 2014 As trurl noted, you must NOT do ANY writes to the array during the parity sync if you want the ability to restore to your old parity drive. Note that IF you should need to do that, you have to do a "New Config" with the "Trust Parity" box checked after you replace the old drive. It's very unlikely that you'll need to do this if you (a) run a parity check immediately before you switch the parity drive, to confirm all is okay (all zeroes); and then (b) do the switch, and simply do not use the array during the initial parity sync on the new (larger) drive. Be sure to run a parity check immediately after the parity sync completes ... a parity sync just writes the parity, it does not validate the writes. Link to comment
jumperalex Posted February 14, 2014 Share Posted February 14, 2014 As trurl noted, you must NOT do ANY writes to the array during the parity sync if you want the ability to restore to your old parity drive. Can you actually write to the array during a parity build? If so, then yes that certainly would be a good thing to avoid if you want to maintain your old parity disk's usefulness (a) run a parity check immediately before you switch the parity drive, to confirm all is okay (all zeroes) huh? "all zeroes" has nothing to do with a validated parity. I'm not saying it is impossible, but I would cry trying to calculate the probability of that happening on a used production array ;-) and then (b) do the switch, and simply do not use the array during the initial parity sync on the new (larger) drive. again, are you actually able to write to the array during a parity build? Be sure to run a parity check immediately after the parity sync completes ... a parity sync just writes the parity, it does not validate the writes. This seems like overkill since you just read the data and wrote the parity bit without a drive reported write error. But hey, whatever keeps you warm at night ;-) Link to comment
JonathanM Posted February 14, 2014 Share Posted February 14, 2014 Be sure to run a parity check immediately after the parity sync completes ... a parity sync just writes the parity, it does not validate the writes. This seems like overkill since you just read the data and wrote the parity bit without a drive reported write error. But hey, whatever keeps you warm at night ;-) There have been several instances of a parity build completing successfully, and then not checking ok. It's not just the write operation completing without error, the drive has to actually read that data before it's any good. Controller errors, RAM errors, drives that return seemingly random values for certain addresses, I think I've seen each of those multiple times in all the years I've been playing with computers. Just like a backup routine that's never been restored and compared to test it, a parity build is suspect until proven otherwise. Link to comment
jumperalex Posted February 14, 2014 Share Posted February 14, 2014 Can't argue with that logic. [tips hat] Link to comment
sureguy Posted February 14, 2014 Share Posted February 14, 2014 As trurl noted, you must NOT do ANY writes to the array during the parity sync if you want the ability to restore to your old parity drive. Can you actually write to the array during a parity build? If so, then yes that certainly would be a good thing to avoid if you want to maintain your old parity disk's usefulness Yes you can, but it will be slow. Link to comment
jumperalex Posted February 14, 2014 Share Posted February 14, 2014 hmmm seems like there should be a setting to disable writes. i guess a reboot into safe more (no plugins) and disconnect the NIC is the best bet for now. Link to comment
garycase Posted February 14, 2014 Share Posted February 14, 2014 Can you actually write to the array during a parity build? If so, then yes that certainly would be a good thing to avoid if you want to maintain your old parity disk's usefulness Yes, you can write to the array during a drive rebuild, whether it's parity or otherwise. But if you do, as I noted earlier, than the parity on the old parity drive will no longer be valid ... so if the goal is to retain the ability to do that (just in case) you should NOT do any writes. huh? "all zeroes" has nothing to do with a validated parity. I'm not saying it is impossible, but I would cry trying to calculate the probability of that happening on a used production array ;-) There's virtually no chance of the parity drive being all zeroes -- nor was I saying that . What I was referring to is all zeroes in the error column and the number of corrected sync errors Those are, of course, what you look at after a parity check. If you do a correcting check (the only kind I ever do), then if they're not all zeroes, if you run it again they should be. If not, then you do NOT want to mess with the array's configuration until you figure out what's wrong. This seems like overkill since you just read the data and wrote the parity bit without a drive reported write error. Yes, you read all the data disks; but the write is NOT validated. True that if the drive logic doesn't report an error it's probably okay; but the drive doesn't read it back either. This true for any rebuild -- whether a data disk or the parity. It's always a good idea to do a parity check after a rebuild to confirm everything went well. Link to comment
axeman Posted February 15, 2014 Author Share Posted February 15, 2014 okay - thanks everyone for the informative replies! the parity build succeeded, and as a few pointed out, i'm going to go ahead and run a sync. I still have another 5 drives to add to this array. After the parity succeeded, i ran a pre-clear -n on the original parity drive. After all of this is said and done, my array will be at the 24TB mark :-)... going up from 10TB. Link to comment
dgaschk Posted February 15, 2014 Share Posted February 15, 2014 Unless you actually need all of the capacity right now, it's a good idea to keep a spare handy. If a drive has a problem you can quickly replace it and have the array protected. Then the problem drive can be pre-cleared at your leisure. If the drive looks good after a pre-clear then it becomes the new spare. Link to comment
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