| | |
Summary: Journal-guided Resynchronization for Software RAID
Timothy E. Denehy, Andrea C. Arpaci-Dusseau, and Remzi H. Arpaci-Dusseau
Department of Computer Sciences, University of Wisconsin, Madison
Abstract
We investigate the problem of slow, scan-based, soft-
ware RAID resynchronization that restores consistency
after a system crash. Instead of augmenting the RAID
layer to quicken the process, we leverage the functional-
ity present in a journaling file system. We analyze Linux
ext3 and introduce a new mode of operation, declared
mode, that guarantees to provide a record of all outstand-
ing writes in case of a crash. To utilize this information,
we augment the software RAID interface with a verify
read request, which repairs the redundant information for
a block. The combination of these features allows us to
provide fast, journal-guided resynchronization. We eval-
uate the effect of journal-guided resynchronization and
find that it provides improved software RAID reliability
and availability after a crash, while suffering little per-
formance loss during normal operation.
|
