Henrique de Moraes Holschuh wrote:
On Tue, 07 Jun 2011, Miles Fidelman wrote:b. you're running RAID - instead of the drive dropping out of the array, the entire array slows down as it waits for the failing drive to (eventually) respond
Linux software raid is much more forgiving by default (and it can tune the timeout for each component device separately), and will just slow down most of the time instead of kicking component devices off the array until dataloss happens. Could be useful if you got duped by the vendor and sold a defective drive that can only operate safely out-of-spec, but can still be useful to you.
Not necessarily the best strategy if you have enough drives to survive 2 drive failures. Sometimes better to have a drive drop out of the array and trigger an alarm than to have a system slow to a crawl precipitously (particularly as that makes it hard to run diagnostics to figure out which drive is bad).
Re. tuning: How? I've tried to find ways to get md to track timeouts, and never been able to find any relevant parameters. Queries to the linux-raid list have yielded some fairly definitive sounding statements, from folks who should know, that md doesn't have any such timeouts. If they're there, please.. more information!
-- In theory, there is no difference between theory and practice. In<fnord> practice, there is. .... Yogi Berra