From: Stefan Kaltenbrunner <stefan@kaltenbrunner.cc>
To: Joshua D. Drake <jd@commandprompt.com>
Cc: jason@ohloh.net <jason@ohloh.net>
Cc: Geoff Tolley <geoff@polimetrix.com>
Cc: pgsql-performance@postgresql.org
Subject: Re: SCSI vs SATA
Date: Wed, 04 Apr 2007 17:33:32 +0200
Message-ID: <4613C54C.4050207@kaltenbrunner.cc> (raw)
In-Reply-To: <4613C14A.4020703@commandprompt.com>
References: <9C0858F5-0A48-4AF9-80FF-E4BA14F0F965@ohloh.net>
<E1HYs6Y-0008O5-SN@elasmtp-banded.atl.sa.earthlink.net>
<E1HYsBX-0006ZE-JG@elasmtp-banded.atl.sa.earthlink.net>
<4613053F.5070401@polimetrix.com>
<DF6C723E-7362-4173-8309-B8AAFC968E2C@ohloh.net>
<4613C14A.4020703@commandprompt.com>
Joshua D. Drake wrote:
>
>>
>> Good point. On another note, I am wondering why nobody's brought up
>> the command-queuing perf benefits (yet). Is this because sata vs scsi
>> are at
>
> SATAII has similar features.
>
>> par here? I'm finding conflicting information on this -- some calling
>> sata's ncq mostly crap, others stating the real-world results are
>> negligible. I'm inclined to believe SCSI's pretty far ahead here but
>> am having trouble finding recent articles on this.
>
> What I find is, a bunch of geeks sit in a room and squabble about a few
> percentages one way or the other. One side feels very l33t because their
> white paper looks like the latest swimsuit edition.
>
> Real world specs and real world performance shows that SATAII performs,
> very, very well. It is kind of like X86. No chip engineer that I know
> has ever said, X86 is elegant but guess which chip design is conquering
> all others in the general and enterprise marketplace?
>
> SATAII brute forces itself through some of its performance, for example
> 16MB write cache on each drive.
sure but for any serious usage one either wants to disable that
cache(and rely on tagged command queuing or how that is called in SATAII
world) or rely on the OS/raidcontroller implementing some sort of
FUA/write barrier feature(which linux for example only does in pretty
recent kernels)
Stefan
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To: pgsql-performance@postgresql.org
Cc: stefan@kaltenbrunner.cc, jd@commandprompt.com, jason@ohloh.net, geoff@polimetrix.com
Subject: Re: SCSI vs SATA
In-Reply-To: <4613C54C.4050207@kaltenbrunner.cc>
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