Journal-guided Resynchronization for Software RAID
Timothy E. Denehy,
Andrea C. Arpaci-Dusseau,
Remzi H. Arpaci-Dusseau
Department of Computer Sciences
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,
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.