RAID 5 max disk nos

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gjb

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Hi,

Is there a recommended or suggested max no of disks that should be placed in
a single RAID-5 array. Recently a SAN engineer suggested that up to 9 is
optimum and that as well as increased risk of multiple disk failure in a
single set, performance is also affected.
We have a no of 15 disk enclosures that historically have been built as
single arrays whereas I think that splitting into 2 x7 with GHS would be
better albeit at the cost of some storage capacity.
Comments appreciated

Geejay
 
Re: RAID 5 max disk nos

In article <ut904HInIHA.2396@TK2MSFTNGP02.phx.gbl>, gjb <gjb@ntl.com>
writes
>Hi,
>
>Is there a recommended or suggested max no of disks that should be placed in
>a single RAID-5 array. Recently a SAN engineer suggested that up to 9 is
>optimum and that as well as increased risk of multiple disk failure in a
>single set, performance is also affected.
>We have a no of 15 disk enclosures that historically have been built as
>single arrays whereas I think that splitting into 2 x7 with GHS would be
>better albeit at the cost of some storage capacity.
>Comments appreciated
>
>Geejay
>
>

I have seen 3, 5, 7, 9, 10, 15 disks in RAID 5.

They all work well under normal running but the larger number the slower
it is if one fails.

On the EMC SANs I work on that have 15 disks to a tray, I tend to slice
into 2 x 7 and a hot spare and use them for the low throughput data
areas. The higher throughput areas I put on 3 x 5.

Don C
 
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