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Re: software vs hw hard on linux

From: aturner(at)neteconomist(dot)com
To: Jeff <threshar(at)torgo(dot)978(dot)org>
Cc: pgsql-performance(at)postgresql(dot)org
Subject: Re: software vs hw hard on linux
Date: 2003-09-12 14:49:24
Message-ID: (view raw, whole thread or download thread mbox)
Lists: pgsql-performance
My personal experience with RAID cards is that you have to spend money to get good performance.  You need battery backed cache because RAID 5 only works well with write to cache turned on, and you need a good size cache too.  If you don't have it, RAID 5 performance will suck big time.  If you need speed, RAID 10 seems to be the only way to go, but of course that means you are gonna spend $$s on drives and chasis.  I wish someone would start a website like for RAID cards because I have had _vastly_ differing experience with different cards.  We currently have a compaq ML370 with a Compaq Smart Array 5300, and quite frankly it sucks (8MB/sec write).  I get better performance numbers off my new Tyan Thunder s2469UGN board with a single U320 10k RPM drive (50MB/sec) than we get off our RAID 5 array including seeks/sec.  Definately shop around, and hopefully some other folks can give some suggestions of a good RAID card, and a good config.

Alex Turner

P.S. If there is movement for a RAID review site, I would be willing to start one, I'm pretty dissapointed at the lack of resources out there for this.

On Fri, Sep 12, 2003 at 10:34:26AM -0400, Jeff wrote:
> Due to various third party issues, and the fact PG rules, we're planning
> on migrating our deplorable informix db to PG.  It is a rather large DB
> with a rather high amount of activity (mostly updates).  So I'm going to
> be aquiring a dual (or quad if they'll give me money) box. (In my testing
> my glorious P2 with a 2 spindle raid0 is able to handle it fairly well)
> What I'm wondering about is what folks experience with software raid vs
> hardware raid on linux is.  A friend of mine ran a set of benchmarks at
> work and found sw raid was running obscenely faster than the mylex and
> (some other brand that isn't 3ware) raids..
> On the pro-hw side you have ones with battery backed cache, chacnes are
> they are less likely to fail..
> On the pro-sw side you have lots of speed and less cost (unfortunately,
> there is a pathetic budget so spending $15k on a raid card is out of the
> question really).
> any thoughts?
> --
> Jeff Trout <jeff(at)jefftrout(dot)com>
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