Isn't this called an active hot spare? I think some hardware RAID controllers offer this feature: Keeping the spare in sync with the whole array, so when a failure happens, the spare takes its place immediately. That'd be an awesome feature to have! On Tue, Oct 13, 2009 at 11:38 PM, Bill Davidsen <davidsen@xxxxxxx> wrote: > Christian Pernegger wrote: >> >> Hi list! >> >> Sometimes I want to exchange a drive in an array even if it hasn't >> actually failed, e. g. >> - in preperation for a grow operation: >> exchange-resync-exchange-resync-...-grow >> - when removing old drives as part of regular maintenance >> - ... >> >> Currently one has to fail an active drive to trigger a resync to the >> replacement (assuming it was added as a spare beforehand) and thus >> suffer the loss of fault tolerance and performance until the sync is >> complete. >> >> Suggestion: allow adding drives as an explicit replacement for an >> active one. The active drive would then be copied to the new one in >> the background, effectively replacing the component device with a >> mirror. Bonus points if the resulting setup is a valid mode of >> operation and not just a temporary hack. I suppose one could see the >> feature as a special case of the reshaping that's all the rage now :) >> > > I think what you want is a subset of the problem many of us face, moving a > member of an array to a larger partition on a (much) larger drive. That > migration, followed by a grow, is getting more appealing, as various drive > drop to "prize in a cereal box" pricing. And as data grows, backup to > something other than disk is getting pretty impractical, resulting in unit > upgrades to save space, time, power, etc, etc. > > I agree with the need, I have several ugly methods of doing this which boil > down to replacing a member with a raid-1 of the member and the new drive. I > have done it several ways, including the "I can't fit another drive in the > box" solution, using nbd and write mostly. Uglier than a hedgehog's ass, but > it worked... eventually. > > -- > Bill Davidsen <davidsen@xxxxxxx> > Unintended results are the well-earned reward for incompetence. > > -- > To unsubscribe from this list: send the line "unsubscribe linux-raid" in > the body of a message to majordomo@xxxxxxxxxxxxxxx > More majordomo info at http://vger.kernel.org/majordomo-info.html > -- Majed B. -- To unsubscribe from this list: send the line "unsubscribe linux-raid" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
