Messages in this thread | | | Date | Tue, 17 Apr 2001 13:53:38 +0200 | From | Ookhoi <> | Subject | Re: fsck, raid reconstruction & bad bad 2.4.3 |
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Hi Linas Vepstas,
(nice name ;-)
> First problem: In kernel-2.4.2 and earlier, if the machine is not cleanly > shut down, then upon reboot, RAID reconstruction is automatically started. > (For RAID-1, this more-or-less ammounts to copying the entire contents > of one disk partition on one disk to another). The reconstruction > code seems to be clever: it will try to use the full bandwidth when > the system is idle, and it will throttle back when busy. It will > only throttle back so far: it tries to maintain at least a minimum amount > of work going, in order to gaurentee forward progress even on a busy system. > > The problem: this dramatically slows fsck after an unclean shut-down. > You can hear the drives machine-gunning. I haven't stop-watch timed it, > but its on the order of 5x slower to fsck a raid partition when there's > reconstruction going on, then when the raid thinks its clean. This > makes unclean reboots quite painful. > > (There is no config file to disable/alter this .. no work-around that I > know of ..)
One possible 'work-around' is to use a journaling filesystem (like reiserfs) which eliminates the fsck after a unclean shutdown. It's very nice to have a crashed system back online fast. The raid sync makes the system a bit slow, but as you said, it syncs at full speed when idle, and is nice when less idle. :-)
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