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    SubjectRe: Raid5 resync slow with one linear array
    On Thu, Apr 04, 2002 at 02:03:16PM +1000, Neil Brown wrote:
    > On Monday April 1, mfedyk@matchmail.com wrote:
    > > Hi,
    > >
    > > I just setup a 4 (5 really) drive raid5 array.
    > >
    > > It is syncing up right now and nothing else is running on the system.
    > >
    > > I have three 18GB SCA scsi drives and 2x9GB linear array in a four "drive"
    > > raid5 array.
    > >
    > > Unfortunately, it is syncing up quite slowly. Only about 2MB/sec on a
    > > 40MB/sec array. The system is idle.
    > >
    > > 2.4.19-pre4-ac3
    > >
    > > Is there something about this config that says "Don't do that!"? I've
    > > heard about RAID10, but not Linear+RAID5...
    >
    > echo 10000 > /proc/sys/dev/raid/speed_limit_min
    >
    > md tries to monitor the activity on the component devices and limits
    > rebuild activity when there appears to be other activity.
    > It measures "other activity" as "blocks added to kstat.dk_drive_?blk",
    > minus "block due to resync activity".
    >
    > When a component device is an md array, nothing gets recorded
    > in kstat, but lots is recorded as resync activity, so this "other
    > activity" appears as a negative number which, due to storage in an
    > unsigned long, appears rather large.
    >
    > NeilBrown

    Yeah, thought it was something like that. Thanks for the explanation. I
    didn't see your message until I sent the other one.

    Mike
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