Re: [gentoo-user] Raid 5 creation is slow - Can this be done quicker? [SOLVED]
On Monday 01 February 2010 12:58:49 J. Roeleveld wrote: > Hi All, > > I am currently installing a new server and am using Linux software raid to > merge 6 * 1.5TB drives in a RAID5 configuration. > > Creating the RAID5 takes over 20 hours (according to " cat /proc/mdstat ") > > Is there a way that will speed this up? The drives are new, but contain > random data left over from some speed and reliability tests I did. I don't > care about keeping the current 'data', as long as when the array is > reliable later. > > Can I use the " --assume-clean " option with mdadm and then expect it to > keep working, even through reboots? > Or is this a really bad idea? > > Many thanks, > > Joost Roeleveld > Hi all, Many thanks for all the input, I did wait the 20 hours, but when it was finished, the performance was still slow. And trying out different options for the array didn't actually help. Thanks to the thread "1-Terabyte drives - 4K sector sizes? -> bar performance so far" I figured out the problem (4KB sectors). After changing the partitions to use sector 64 as start (as opposed to 63) a build of the array should only take 6 hours. Hopefully, the raid-array will also show a better performance when this is finished. -- Joost Roeleveld
Re: [gentoo-user] Raid 5 creation is slow - Can this be done quicker?
>> It would be interesting to know whether hardware RAID would behave any >> differently or allow the sync to perform in the background. I have >> only 1.5TB in RAID5 across 4 x 500gb drives at present; IIRC the >> expansion from 3 x drives took some hours, but I can't recall the >> initial setup. LSI, 3ware and Areca hardware raid controllers are capable of doing a background init but their performance is impacted, I can't speak on other controllers as I haven't used them before. I've built many RAID6 arrays with all three controllers - 8x 1TB and 8x 1.5TB and I'll usually start a foreground init and let them run overnight because it does take a long time. Also, RAID10 is much faster to get up and running because it doesn't have to calculate parity. -- Kyle
Re: [gentoo-user] Raid 5 creation is slow - Can this be done quicker?
On Monday 01 February 2010 14:20:28 Stroller wrote: > On 1 Feb 2010, at 11:58, J. Roeleveld wrote: > > ... > > I am currently installing a new server and am using Linux software > > raid to > > merge 6 * 1.5TB drives in a RAID5 configuration. > > > > Creating the RAID5 takes over 20 hours (according to " cat /proc/ > > mdstat ") > > > > Is there a way that will speed this up? The drives are new, but > > contain random > > data left over from some speed and reliability tests I did. I don't > > care about > > keeping the current 'data', as long as when the array is reliable > > later. > > > > Can I use the " --assume-clean " option with mdadm and then expect > > it to keep > > working, even through reboots? > > Or is this a really bad idea? > > It wasn't my intention to chide you - I don't use software RAID > myself, and your question piqued my curiosity - but the first three > Google hits for "assume-clean" indicate that this isn't safe to use > with RAID5. > > The 4th Google hit contains an extract from the manpage: > >... It can >also be used when creating a RAID1 or RAID10 if you want >to avoid the initial resync, however this practice -- >while normally safe -- is not recommended. Use this >only if you really know what you are doing. I did find the same results on Google, but not really a proper explanation as to why it's a "bad idea". Unfortunately, my budget doesn't extend to a hardware raid solution. (The cheap cards offload it to the CPU anyway and are generally considered slower in various benchmarks) > I kinda expected this 20 hours to be spent verifying that the disks > contain no bad sectors, which would really hose you if it were the case. True, but I already ran "badblocks" twice on each disk to verify that the disks are fine. (No badblocks found). > But OTOH, 20 hours does not seem an outrageous amount of time for > building a 7.5TB array. You're not going to do this often, and you > want it done right. Good point, and I agree, which is why I will let it finish it's course, but I also expected it could be done quicker. > It would be interesting to know whether hardware RAID would behave any > differently or allow the sync to perform in the background. I have > only 1.5TB in RAID5 across 4 x 500gb drives at present; IIRC the > expansion from 3 x drives took some hours, but I can't recall the > initial setup. I'm hoping someone with more knowledge about RAID-systems can throw in his/her 2cents. Thanks, Joost
Re: [gentoo-user] Raid 5 creation is slow - Can this be done quicker?
On 1 Feb 2010, at 11:58, J. Roeleveld wrote: ... I am currently installing a new server and am using Linux software raid to merge 6 * 1.5TB drives in a RAID5 configuration. Creating the RAID5 takes over 20 hours (according to " cat /proc/ mdstat ") Is there a way that will speed this up? The drives are new, but contain random data left over from some speed and reliability tests I did. I don't care about keeping the current 'data', as long as when the array is reliable later. Can I use the " --assume-clean " option with mdadm and then expect it to keep working, even through reboots? Or is this a really bad idea? It wasn't my intention to chide you - I don't use software RAID myself, and your question piqued my curiosity - but the first three Google hits for "assume-clean" indicate that this isn't safe to use with RAID5. The 4th Google hit contains an extract from the manpage: ... It can also be used when creating a RAID1 or RAID10 if you want to avoid the initial resync, however this practice -- while normally safe -- is not recommended. Use this only if you really know what you are doing. I have to say that I don't fully understand this. I would have thought that one could pretend the entire array was empty, and the RAID driver would just overwrite the disk as you write to the filesystem. The parts used by the filesystem are the only parts you care about, and I wouldn't have thought it would matter if the unused parts weren't in sync. I would be delighted if someone could explain me. I kinda expected this 20 hours to be spent verifying that the disks contain no bad sectors, which would really hose you if it were the case. But OTOH, 20 hours does not seem an outrageous amount of time for building a 7.5TB array. You're not going to do this often, and you want it done right. It would be interesting to know whether hardware RAID would behave any differently or allow the sync to perform in the background. I have only 1.5TB in RAID5 across 4 x 500gb drives at present; IIRC the expansion from 3 x drives took some hours, but I can't recall the initial setup. Stroller.
Re: [gentoo-user] Raid 5 creation is slow - Can this be done quicker?
Most of the wait I would assume is due to the size of the volume and creating parity. If it was my array I'd probably just sit tight and wait it out. On 2/1/10, J. Roeleveld wrote: > Hi All, > > I am currently installing a new server and am using Linux software raid to > merge 6 * 1.5TB drives in a RAID5 configuration. > > Creating the RAID5 takes over 20 hours (according to " cat /proc/mdstat ") > > Is there a way that will speed this up? The drives are new, but contain > random > data left over from some speed and reliability tests I did. I don't care > about > keeping the current 'data', as long as when the array is reliable later. > > Can I use the " --assume-clean " option with mdadm and then expect it to > keep > working, even through reboots? > Or is this a really bad idea? > > Many thanks, > > Joost Roeleveld > > -- Sent from my mobile device Kyle
[gentoo-user] Raid 5 creation is slow - Can this be done quicker?
Hi All, I am currently installing a new server and am using Linux software raid to merge 6 * 1.5TB drives in a RAID5 configuration. Creating the RAID5 takes over 20 hours (according to " cat /proc/mdstat ") Is there a way that will speed this up? The drives are new, but contain random data left over from some speed and reliability tests I did. I don't care about keeping the current 'data', as long as when the array is reliable later. Can I use the " --assume-clean " option with mdadm and then expect it to keep working, even through reboots? Or is this a really bad idea? Many thanks, Joost Roeleveld
