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: 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] > 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
_______________________________________________ zfs-discuss mailing list zfs-discuss@opensolaris.org http://mail.opensolaris.org/mailman/listinfo/zfs-discuss
