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Re: sipping lightly or drinking deeply from the ASM koolaid?

From: <pdxkevinc_at_gmail.com>
Date: 27 Nov 2006 16:21:27 -0800
Message-ID: <1164673287.161585.72550@j44g2000cwa.googlegroups.com>

uality and timely support
> > from any of our big vendors.
>
> IIRC, he is the chief architect for polyserve, which makes...HA NAS
> filesystem software/utilities. I know some people run ASM on NAS, but
> it always seemed a bit kludgy to me. From what I have read by him
> (other whitepapers in addition to the link you provided), he is a
> really smart guy, it just looks like he may not be completely unbiased.

I am not unbiased and I hope it hasn't sounded as though I'm presenting myself as such on my blog. I do try my best to fortify all my positions with as much fact as possible though.

>
> We have a 2.5TB non RAC data warehouse on ASM (which lives on an EMC
> DMx), and we get 6-7ms single block reads with no
> performance/availability issues at all. I understand the need to
> diversify your vendors, but I also see value in the firm that provides
> the RDBMS software also providing the filesystem to which the RDBMS I/O
> requests will be made.

If you read enough of my blog postings, you'll see that I'm not suggesting ASM doesn't work. I have been trying to make the point that it is a tool that should not be force-fed into all deployment scenarios--most notably in a commodity computing paradigm.And even more so not with NAS.

 I don't doubt your I/O latency measurements at all. ASM is __not__ in the I/O code path. The ASM extent pointer array is cached in each SGA so an I/O can be shot off to an offset in an ASM disk without comms (OCI) with the ASM instance...the latter happening mostly when the structure of objects stored in ASM change.

As an aside, do all your RAC SGAs have the same ASM extent pointer array content?

http://kevinclosson.wordpress.com/

>
> Regards,
>
> Steve
Received on Mon Nov 27 2006 - 18:21:27 CST

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