4th USENIX Conference on File and Storage TechnologiesAbstract
Pp. 87100 of the Proceedings
Journal-guided Resynchronization for Software RAID
Timothy E. Denehy, Andrea C. Arpaci-Dusseau, and Remzi H. Arpaci-Dusseau, University of Wisconsin, Madison
We investigate the problem of slow, scan-based, software
RAID resynchronization that restores consistency
after a system crash. Instead of augmenting the RAID
layer to quicken the process, we leverage the functionality
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 outstanding
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 evaluate
the effect of journal-guided resynchronization and
find that it provides improved software RAID reliability
and availability after a crash, while suffering little performance
loss during normal operation.
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