Hi Toby, You're right. The healthcheck would definitely find any issues. I misinterpreted your comment to that effect as a question and didn't quite latch on. A zpool MAID-mode with that healthcheck might also be interesting on something like a Thumper for pure-archival, D2D backup work. Would dramatically cut down on the power. What do y'all think?
Best Regards, Jason On 1/29/07, Toby Thain <[EMAIL PROTECTED]> wrote:
On 29-Jan-07, at 11:02 PM, Jason J. W. Williams wrote: > Hi Guys, > > I seem to remember the Massive Array of Independent Disk guys ran into > a problem I think they called static friction, where idle drives would > fail on spin up after being idle for a long time: You'd think that probably wouldn't happen to a spare drive that was spun up from time to time. In fact this problem would be (mitigated and/or) caught by the periodic health check I suggested. --T > http://www.eweek.com/article2/0,1895,1941205,00.asp > > Would that apply here? > > Best Regards, > Jason > > On 1/29/07, Toby Thain <[EMAIL PROTECTED]> wrote: >> >> On 29-Jan-07, at 9:04 PM, Al Hopper wrote: >> >> > On Mon, 29 Jan 2007, Toby Thain wrote: >> > >> >> Hi, >> >> >> >> This is not exactly ZFS specific, but this still seems like a >> >> fruitful place to ask. >> >> >> >> It occurred to me today that hot spares could sit in standby (spun >> >> down) until needed (I know ATA can do this, I'm supposing SCSI >> does >> >> too, but I haven't looked at a spec recently). Does anybody do >> this? >> >> Or does everybody do this already? >> > >> > I don't work with enough disk storage systems to know what is the >> > industry >> > norm. But there are 3 broad categories of disk drive spares: >> > >> > a) Cold Spare. A spare where the power is not connected until >> it is >> > required. [1] >> > >> > b) Warm Spare. A spare that is active but placed into a low power >> > mode. ... >> > >> > c) Hot Spare. A spare that is spun up and ready to accept >> > read/write/position (etc) requests. >> >> Hi Al, >> >> Thanks for reminding me of the distinction. It seems very few >> installations would actually require (c)? >> >> > >> >> Does the tub curve (chance of early life failure) imply that hot >> >> spares should be burned in, instead of sitting there doing nothing >> >> from new? Just like a data disk, seems to me you'd want to know >> if a >> >> hot spare fails while waiting to be swapped in. Do they get tested >> >> periodically? >> > >> > The ideal scenario, as you already allude to, would be for the disk >> > subsystem to initially configure the drive as a hot spare and >> send it >> > periodic "test" events for, say, the first 48 hours. >> >> For some reason that's a little shorter than I had in mind, but I >> take your word that that's enough burn-in for semiconductors, motors, >> servos, etc. >> >> > This would get it >> > past the first segment of the "bathtub" reliability curve ... >> > >> > If saving power was the highest priority, then the ideal situation >> > would >> > be where the disk subsystem could apply/remove power to the spare >> > and move >> > it from warm to cold upon command. >> >> I am surmising that it would also considerably increase the spare's >> useful lifespan versus "hot" and spinning. >> >> > >> > One "trick" with disk subsystems, like ZFS that have yet to have >> > the FMA >> > type functionality added and which (today) provide for hot spares >> > only, is >> > to initially configure a pool with one (hot) spare, and then add a >> > 2nd hot >> > spare, based on installing a brand new device, say, 12 months >> > later. And >> > another spare 12 months later. What you are trying to achieve, >> > with this >> > strategy, is to avoid the scenario whereby mechanical systems, like >> > disk >> > drives, tend to "wear out" within the same general, relatively >> short, >> > timeframe. >> > >> > One (obvious) issue with this strategy, is that it may be >> > impossible to >> > purchase the same disk drive 12 and 24 months later. However, it's >> > always >> > possible to purchase a larger disk drive >> >> ...which is not guaranteed to be compatible with your storage >> subsystem...! >> >> --Toby >> >> > and simply commit to the fact >> > that the extra space provided by the newer drive will be wasted. >> > >> > [1] The most common example is a disk drive mounted on a carrier >> > but not >> > seated within the disk drive enclosure. Simple "push in" when >> > required. >> > ... >> > Al Hopper Logical Approach Inc, Plano, TX. [EMAIL PROTECTED] >> approach.com >> > Voice: 972.379.2133 Fax: 972.379.2134 Timezone: US CDT >> > OpenSolaris.Org Community Advisory Board (CAB) Member - Apr 2005 >> > OpenSolaris Governing Board (OGB) Member - Feb 2006 >> >> _______________________________________________ >> zfs-discuss mailing list >> zfs-discuss@opensolaris.org >> http://mail.opensolaris.org/mailman/listinfo/zfs-discuss >>
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