On Sunday 16 December 2007 23:36:21 SJS wrote: > begin quoting David Brown as of Sun, Dec 16, 2007 at 02:19:44PM -0800: > > On Sun, Dec 16, 2007 at 02:11:59PM -0800, SJS wrote: > > >A hardware RAID controller can write to each disk in parallel, computing > > >the necessary checksums, etc., while a JBOD with a single controller > > >will need to write to each disk separately (if the data is to span > > >multiple disks). > > > > Software RAID can do this as well, if you're willing to put each drive on > > a separate bus, and the OS and the rest of the architecture can handle > > it. > > Yeah, but that extra hardware starts pushing you in to hardware RAID > territory. The line is a bit fuzzy.. > > > You do have to compute checksums with one of the CPUs on the host. This > > becomes more of a problem with more complex parity algorithsm, such as > > RAID-6 uses. > > I think we probably have enough excess CPU processing power to mitigate > the cost of computing a checksum.
Not really. My fileserver as an A64 3400+ CPU and still can't go past 10MB/s write speed on a 4x250GB array. Dex -- -----BEGIN GEEK CODE BLOCK----- Version: 3.12 GCS d--(+)@ s-:+ a- C++++ UL++ P+>++ L+++>++++ E-- W++ N o? K- w--(---) !O M+ V- PS+ PE Y++ PGP t++(---)@ 5 X+(++) R+(++) tv--(+)@ b++(+++) DI+++ D- G++ e* h>++ r* y? ------END GEEK CODE BLOCK------ http://www.stop1984.com http://www.againsttcpa.com -- [email protected] http://www.kernel-panic.org/cgi-bin/mailman/listinfo/kplug-list
