On Fri, 26 Jul 2013 11:48:28 +1000 Craig Sanders <cas@taz.net.au> wrote:
On Thu, Jul 25, 2013 at 06:31:54PM +1000, Russell Coker wrote:
I'm getting some errors on a zpool scrub operation. It's obvious that sdd has the problem both from the below output of zpool status and from the fact that the kernel message log has read errors about sdd.
what sort of controller is it on, and do you have standby/spin-down enabled? that can cause drives to be booted from a raid array or zpool if they don't respond fast enough.
that's the reason for using IT mode firmware rather than RAID mode firmware in LSI and similar cards - it's far more forgiving of consumer drives and their slow responses when waking up from standby. RAID mode firmware pretty much expects enterprise drives with standby disabled.
It's the onboard controller on a Dell PowerEdge T110, a fairly basic SATA controller. I don't think that spin-down is the issue, if it was then it would affect all disks in the set, it wouldn't give kernel read error messages, and it would only affect the start of the scrub process not happen throughout the scrub.
zpool status will tell you how much data was corrected when it has finished.
e.g. on my backup pool, zpool status says this:
scan: scrub repaired 160K in 4h21m with 0 errors on Sat Jul 20 06:03:58 2013
also the numbers in the READ WRITE and CKSUM columns will show you the number of errors detected for each drive.
However those numbers are all 0 for me. I'm now replacing the defective disk. I've attached a sample of iostat output, it seems to be reading from all disks and then reconstructing the parity for the new disk which is surprising, I had expected it to just read the old disk and write to the new disk but instead I get a scrub as well as the "resilver". So the rate of rebuild is considerably less than half what I had hoped for, I had expected something like 130MB/s for contiguous reads and writes and instead each of the 5 disks is doing about 45MB/s. -- My Main Blog http://etbe.coker.com.au/ My Documents Blog http://doc.coker.com.au/