On 9/10/07, Pawel Jakub Dawidek <[EMAIL PROTECTED]> wrote: > Hi. > > I've a prototype RAID5 implementation for ZFS. It only works in > non-degraded state for now. The idea is to compare RAIDZ vs. RAID5 > performance, as I suspected that RAIDZ, because of full-stripe > operations, doesn't work well for random reads issued by many processes > in parallel. > > There is of course write-hole problem, which can be mitigated by running > scrub after a power failure or system crash.
If I read your suggestion correctly, your implementation is much more like traditional raid-5, with a read-modify-write cycle? My understanding of the raid-z performance issue is that it requires full-stripe reads in order to validate the checksum. So to get better random read performance, why not simply have a separate checksum for each chunk in the stripe? You still eliminate the raid-5 write hole (albeit at some loss in performance because you have to compute and write extra checksums) but you allow multiple independent reads. -- -Peter Tribble http://www.petertribble.co.uk/ - http://ptribble.blogspot.com/ _______________________________________________ zfs-discuss mailing list zfs-discuss@opensolaris.org http://mail.opensolaris.org/mailman/listinfo/zfs-discuss
