Date: Wed, 3 Sep 2003 12:47:34 -0700 From: Brooks Davis <brooks@one-eyed-alien.net> To: Chuck Swiger <cswiger@mac.com> Cc: freebsd-performance@freebsd.org Subject: Re: 20TB Storage System (fsck????) Message-ID: <20030903194734.GA7936@Odin.AC.HMC.Edu> In-Reply-To: <3F5642FF.6060702@mac.com> References: <ILENIMHFIPIBHJLCDEHKOECFDDAA.max.clark@media.net> <3F5634FE.9080303@mac.com> <20030903184506.GC14797@sgh.waw.pl> <3F5642FF.6060702@mac.com>
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[-- Attachment #1 --] On Wed, Sep 03, 2003 at 03:37:35PM -0400, Chuck Swiger wrote: > Piotr KUCHARSKI wrote: > >On Wed, Sep 03, 2003 at 02:37:50PM -0400, Chuck Swiger wrote: > >>I'm wary of the write-performance hit from putting too many drives wide > >>in a RAID-5 (or -5,0) configuration. > > > >How many is "too many"? > > At one point, the advice used to be to use between four and seven disks for > a RAID-5 volume. For example, the Apple XServe RAID box has 14 bays, but > Apple seems to recommend configuring it as two 7-drive RAID-5 volumes, > rather than a single 14-drive-wide RAID-5 volume. As far as I can tell from taking one of ours apart, that's not recommendation, that's a hard limit due to the system design. The XServe RAID is two 100% independent 7-disk RAID systems. If you look at the controller boards, each one has four High-Point ATA controllers which means it can only access 8 disks with reasonable performance. There appears to be no communication between the halves of the systems. -- Brooks -- Any statement of the form "X is the one, true Y" is FALSE. PGP fingerprint 655D 519C 26A7 82E7 2529 9BF0 5D8E 8BE9 F238 1AD4 [-- Attachment #2 --] -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.2.1 (GNU/Linux) iD8DBQE/VkVVXY6L6fI4GtQRAjH7AJ0Wy7SliPnuHDctJtcZ4o2XA7B9JACgtVwq rl01HZTF3w6O3FU1qMi2BTY= =K9k3 -----END PGP SIGNATURE-----
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