On Thu, Oct 6, 2011 at 1:03 PM, Paul Hartman <paul.hartman+gen...@gmail.com> wrote: > On Thu, Oct 6, 2011 at 2:44 PM, Mark Knecht <markkne...@gmail.com> wrote: >> Paul, >> Would hdparm be advisable if the drive was part of a RAID? I suspect not. >> >> I don't think this applies to the OP but for the sake of discussion >> why not include RAID as part of the solution, if possible. > > I use hdparm to set power-saving on all members of my RAID5 and it > works (in my case, I'm setting them to never spin-down). I created a > file /etc/local.d/hd-power-level-fix.start containing one line: > > hdparm -B 254 /dev/sd[abcdef] > > which automatically sets those drives to never spin down. > > In my original recommendation, I hadn't considered hdparm's "spindown > immediately" option. I was thinking of the -B command like I used > above, to adjust the "spin down after X idle time" option. If all > members of the RAID have the same idle time they'll probably all spin > up and down together under normal usage (well, depending what kind of > RAID it is, I suppose). In my case, I found the "click, whirr, click, > whirr, click, whirr, click, whirr, click, whirr" waiting for 5 disks > to spin-up when I accessed the RAID annoying, so I disabled it. (I > have not done any power-consumption measurements to see what that's > costing me...) >
My worry was that if the mdraid daemon saw one drive gone - either when starting to spin down or when one spins up slowly - and if mdraid didn't understand that all this stuff was taking place intentionally then it might mark that drive as having failed. I can see the utility of spinning down a RAID in something like a home video server where I keep movies. The machine could be on, ready to serve a movie, but the drives aren't drawing much power. I suspect that there's a pretty substantial power savings on a big RAID if done right, but I haven't done any measurements either. Cheers, Mark
