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Re: RAID6 r-m-w, op-journaled fs, SSDs

To: xfs@xxxxxxxxxxx
Subject: Re: RAID6 r-m-w, op-journaled fs, SSDs
From: Michael Monnerie <michael.monnerie@xxxxxxxxxxxxxxxxxxx>
Date: Sat, 30 Apr 2011 23:50:31 +0200
Cc: Stan Hoeppner <stan@xxxxxxxxxxxxxxxxx>
In-reply-to: <4DBC68DA.1090708@xxxxxxxxxxxxxxxxx>
Organization: it-management http://it-management.at
References: <19900.10868.583555.849181@xxxxxxxxxxxxxxxxxx> <20110430180213.6dcfc41c@xxxxxxxxxxxxxxx> <4DBC68DA.1090708@xxxxxxxxxxxxxxxxx>
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On Samstag, 30. April 2011 Stan Hoeppner wrote:
> Poor cache management, I'd guess, is one reason why you see Areca
> RAID  cards with 1-4GB cache DRAM whereas competing cards w/ similar
> price/performance/features from LSI, Adaptec, and others sport
> 512MB.

On one server (XENserver virtualized with ~14 VMs running Linux) which 
suffered from slow I/O on RAID-6 during heavy times, I upgraded the 
cache from 1G to 4G using an Areca ARC-1260 controller (somewhat 
outdated now), and couldn't see any advantage. Maybe it would have been 
measurable, but the damn thing was still pretty slow, so using more hard 
disks is still the better option than upgrading the cache.

Just for documentation if someone sees slow I/O on Areca. More spindles 
rock. That server had 8x 10krpm WD Raptor 150G drives by the time.

-- 
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Michael Monnerie, Ing. BSc

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