Date: Thu, 23 Sep 1999 02:25:26 -0700 (PDT) From: Matthew Dillon <dillon@apollo.backplane.com> To: current@freebsd.org Subject: CCD update committed Message-ID: <199909230925.CAA23816@apollo.backplane.com>
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I've made a bunch of fixes and enhancements to CCD. I do not believe
I've messed anything up but CCD is rather messy so I'm doing a little
head's up anyway.
* CCD panic when underlying storage has a sector size larger then 1K
fixed.
* CCD lockup when dd'ing from the raw ccd device using a block size
that causes the CCD partition's EOF to occur in the middle of an
I/O fixed.
* CCD complains to dmesg (but does not yet cause a configuration failure)
if you try to use a mirror with an interleave of 0.
* MIRRORing code enhanced:
- When reading, CCD will issue the read from either side of the
mirror. CCD now implements a zone selector to try to optimize
which disk is selected based on seek proximity.
- If a read error occurs, CCD will automatically try to recover by
reading from the other side of the mirror. If this also fails, the
read error is propogated back.
Note that CCD's mirroring has never been and still does not use any
formal recovery mechanisms. You cannot replace a disk in the mirror
and expect to get something coherent out of it. You can turn off a
disk in the mirror by unmounting the CCD and reconfiguring it without
the mirror disks as a non-mirror CCD, but that's about it. Replacing
a bad disk effectively requires backing up the good one, replacing
the disk, and then regenerating (to be safe) both disks from the backup.
The parity stuff never worked and probably never will.
-Matt
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