On Thu, Oct 6, 2011 at 3:21 PM, Mark Knecht <markkne...@gmail.com> wrote: > 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.
The drive's not gone, it's not offline, it's just not spinning. I don't think mdraid would even know that.
