On Wednesday, April 13, 2011 09:18 PM, Ross Walker wrote: > On Apr 13, 2011, at 8:45 AM, Christopher > Chan<christopher.c...@bradbury.edu.hk> wrote: > >> On Wednesday, April 13, 2011 04:00 PM, Sorin Srbu wrote: >> >>> With today's CPU-performance and RAM available, software raids are not a >>> problem >>> to power. >>> >> >> That depends. Software raid is fine for raid1 and raid0. If you want >> raid5 or raid6, you have to use hardware raid with bbu cache that >> matches the size of the array notwithstanding the limiting to 10 disks >> max. consideration. >> >> cpu performance/amount of RAM available is a non-issue and has been for >> a decade. > > The battery backed cache is essential in avoiding the parity write hole as > well as avoiding the performance penalty of short writes, those less then the > stripe width where the remaining chunks need to be read to calculate the new > parity, as the cache can attempt to cache the write until it gets a full > stripe width and/or cache future writes until the read-calc-write is > completed. >
While we are at it, disks being directly connected to the raid card will mean there won't be bus contention from nics and what not whereas software raid 5/6 would have to deal with that. _______________________________________________ CentOS mailing list CentOS@centos.org http://lists.centos.org/mailman/listinfo/centos
