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
