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Re: Best hardware/cost tradoff?

From: "Scott Marlowe" <scott(dot)marlowe(at)gmail(dot)com>
To: "Fernando Hevia" <fhevia(at)ip-tel(dot)com(dot)ar>
Cc: cluster <skrald(at)amossen(dot)dk>, pgsql-performance(at)postgresql(dot)org
Subject: Re: Best hardware/cost tradoff?
Date: 2008-08-28 21:47:37
Message-ID: (view raw, whole thread or download thread mbox)
Lists: pgsql-performance
On Thu, Aug 28, 2008 at 2:04 PM, Fernando Hevia <fhevia(at)ip-tel(dot)com(dot)ar> wrote:
> I havent had any issues with software raid (mdadm) and hot-swaps. It keeps
> working in degraded mode and as soon as you replace the defective disk it
> can reconstruct the array on the fly. Performance will suffer while at it
> but the service keeps up.

I too put my vote behind mdadm for ease of use.  However, there are
reports that certain levels of RAID in linux kernel RAID that are
supposed to NOT handle write barriers properly.  So that's what
worries me.

> The battery backup makes a very strong point for a hw controller. Still, I
> have heard good things on combining a HW controller with JBODS leaving the
> RAID affair to mdadm. In your scenario though with "*lots* of random reads",

This is especially true on slower RAID controllers.  A lot of RAID
controllers in the $300 range with battery backed caching don't do
RAID real well, but do caching ok.  If you can't afford a $1200 RAID
card then this might be a good option.

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