From: Michael Monnerie <michael.monnerie@is.it-management.at>
To: xfs@oss.sgi.com
Subject: Re: data switchs su,sw and sunit,swidth
Date: Mon, 20 Jul 2009 13:22:21 +0200 [thread overview]
Message-ID: <200907201322.22102@zmi.at> (raw)
In-Reply-To: <4A626EC5.3090100@tlinx.org>
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On Sonntag 19 Juli 2009 Linda Walsh wrote:
> Then, for RAID 1 (mirror) would 'sw'==1? Would setting the su/sw
> value for a RAID 1 actually matter in any way? Ie, technically --
> it would fill in numbers for OS book-keeping, but wouldn't change
> anything in terms of performance or layout, vs. 'physically' -- where
> it could change disk layout or performance?
>
> At RAID 0, I'd guess sw==2?
Both RAID0 and RAID1 use sw=0.
> In RAID 5, would it be sw == #Disks-1? So even w/6 disks, it
> still only uses 1 disk for parity and sw == 5?
RAID5: sw = #Disks-1 ( so with 8 disks use 7)
RAID6: sw = #Disks-2 ( so with 8 disks use 6)
> I wonder what becomes a max-safe RAID 5 size? (or is the number of
> parity disks a settable option with RAID 5?)
RAID5 always only has 1 parity disk (well, technically it's not a
physical disk, but the parity is distributed over all disks in the
array).
Don't know what you mean by "max-safe" size. The more disks you have,
the bigger the chance that a single disk breaks. Also, I tested with
Areca controllers, using more than 7 disks in a single RAID array
doesn't improve speed anymore. So I use RAID-6 for up to 8 disks, and
make it RAID-60 for up to 16 disks (with Areca controllers).
mfg zmi
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prev parent reply other threads:[~2009-07-20 11:21 UTC|newest]
Thread overview: 2+ messages / expand[flat|nested] mbox.gz Atom feed top
2009-07-19 0:54 data switchs su,sw and sunit,swidth Linda Walsh
2009-07-20 11:22 ` Michael Monnerie [this message]
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