Re: Storage array advice anyone?

Amir,

Obviously, you need more cache :).

(ducking and running)

It might be that you're saturated at the controller (FCHBAs - host bus adapter(s)) or in internal bandwidth - depends upon the number of paths allocated to your mount points.

Paul

On Wed, 15 Dec 2004 20:34:40 -0000, Barr, Stephen <Stephen.Barr_at_bskyb.com> wrote:
> Hi Amir,
> We also have a DMX 3000 box and have it striped 8 ways.
>
> We have 83 meta devices, each meta device is ~67Gb is size and is
> made of eight 8.43Gb volumes. Each volume is RAID 1, however, each meta
> volume is striped across it's eight individual volumes with a stripe size of
> 0.94Mb.
>
> The issue we have at present is that we are a datawarehouse doing
> lots of 1Mb direct path reads. Each read will hit 8 physical devices (with
> 1Mb stripe unit size at OS). I assuming this is a bad thing - surely each of
> our reads should be hitting only a single device? i.e. we're waiting on 8
> devices instead of only one.
>
> I've performed a number of tests with PQ on the current setup, and
> it looks like the IO subsystem is saturated with a single PQ query (degree
> 4) to such an extent that two PQ queries running together BOTH take twice as
> long to complete....surely this isn't the pattern we should be seeing? It
> essentially means that the system is 100% non-scalable.
>
> 1 query PARALLEL 4 (FTS)
>
> 1Mb Stripe unit 5 mins 18 secs
> 512k Stripe unit 5 mins 18 secs
> 128k Stripe unit 5 mins 52 secs
> CONCAT 5 mins 10 secs
>
> 2 queries hitting same table PARALLEL 4 (FTS)
>
> 1Mb Stripe unit 8 mins 43 secs (each)
> 512k Stripe unit 10 mins 12 secs (each)
> 128k Stripe unit 8 mins 35 secs (each)
> CONCAT 8 mins 10 secs (each)
>
> Does anyone have any experience of setting up this type of storage solution
> for a data warehouse?
>
> Thanks,
>
> Steve.

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