On 10 October 2013 22:27, steve-ALUG@hst.me.uk wrote:
Out of interest, I wonder if
hdparm -I /dev/sda
shows anything interesting, adjusting to your drive names as appropriate.
Define "interesting"!
See http://pastebin.com/bAxaa1BH
This thread was quite interesting http://ubuntuforums.org/archive/index.php/t-1681924.html
Thanks for that, interesting reading.
So, it seems that some WD Green drives have had problems, that seem to be solved (at least once) by disabling NCQ - Native Command Queuing.
OK, sounds like it wouldn't do me any harm to disable it (hdparm confirms it's enabled). However the two steps of performing a zero-fill, then setting the idle time to 300s, prior to rebuilding the array has resulted in a fully functioning array this morning. My instinct is that it was the idle timeout change that fixed it, particularly in light of the thread you found.
I do have another RAID5 array in another box, also using WD drives (identical drives I think) that never presented an issue in building or in use, although I suspect now that the discs have taken an undue hammering and need to be pensioned off early.
It appears that NCQ can be disabled by
$ echo 1 > /sys/block/sda/device/queue_depth $ echo 1 > /sys/block/sdb/device/queue_depth
I note that hdparm -Q can report and set the queue depth (currently set to 31). Any suggestions from anyone as to which way I *should* disable NCQ?
It also occurs me that perhaps the drives have acoustic management (i.e. quiet mode) which may slow things down or cause problems. If it's still not working, perhaps try to turn that off too.
As far as I can tell these drives don't have a configurable acoustic management, they're just tuned to low energy use
Meanwhile, can anyone recommend a good choice of desktop drives for a simple RAID5 array? By "simple" I mean for basically a NAS box storing various files for occasional use in an office with two people in it, so not heavy usage. Obviously a set of SAS disks in a decent server would be preferable but I don't have the budget for that, and I know what the "I" in RAID stands for...