20TB Storage System (fsck????)

[Brooks Davis]

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.
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