Le Wed, 27 Oct 2010 09:00:06 +0200
Stefan Priebe - Profihost AG <s.priebe@xxxxxxxxxxxx> écrivait:
> So what values do you recommand in general for iSCSI on Serverside
> and which values on iSCSI client side?
>
Depends upon the hardware. nr_requests should be 512 for 3Ware cards,
256 to 1024 for other controllers (always more than the default 128
anyway).
Same rule goes for read-ahead; however many RAID controllers (Areca,
Adaptec) "cheat" and do read-ahead optimisation by themselves (which
may harm random access). The default read-ahead value (256) was OK for
obsolete ATA drives with a few KB of cache; nowadays all drives have 32
or 64 MB, and controllers 512 MB to several GB, so more read-ahead can
do no harm but fill the cache up. I often go up to 65536 or 131072
sectors (for 24 or 48 drives arrays). Keep in mind that this is
sequentail-raid optimisation; random access (such as VM work) may give
better result with lower read-ahead values. Benchmarking your
application is king here.
Just for information : I currently run some servers with kernel
2.6.22.18 (march 2008) and 3Ware firmware 4.10.0.7, so upgrading your
2.6.23 system should be perfectly safe from a driver compatibility
point of view.
--
------------------------------------------------------------------------
Emmanuel Florac | Direction technique
| Intellique
| <eflorac@xxxxxxxxxxxxxx>
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