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Re: How many of you use S.A.M.E?

From: amonte <ax.mount_at_gmail.com>
Date: Fri, 2 Feb 2007 00:45:12 +0100
Message-ID: <85c1fb130702011545t536b4c24g1daa14ac81dc23d1@mail.gmail.com>


Hi

Its Symmetrix, DMX XXX not sure about the model. It's not that new, probably 2.5 years.

Regarding the slices, the EMC guy told me that this ship the storage that way only when customers are in hurry, usually they do better jobs he said.

BTW I also heard quite a few time that disabling the write cache improves perormance but is that ritten anywhere? Imagine I tell the SAN admin to disable the cache he would probably say... "WTF are you talking about" :-P

Thanks

Alex

On 2/2/07, Bryan Thomas <bthomas_at_perftuning.com> wrote:
>
> Alex,
>
>
>
> Are you using a Clariion or a Symetrix? There is a big difference in how
> these are configured.
>
>
>
> I mainly have experience setting up Clariions.
>
>
>
> A Meta is probably a Meta LUN made up of multiple LUN's. The Meta-LUN
> allow you to add drives to LUN without having to reconfigure the OS.
>
>
>
> As for performance, it seems that you do have an I/O issue. This is
> probably due to not enough spindles. You really need more disks. The
> Meta-LUNs and SAME just try and spread the load across all of your available
> spindles.
>
>
>
> If you are using 120 Disks in a RAID 1+0 configuration with 256 GB drives,
> you probably have 10k speed spindles. This is slow in this day and age.
> You can do approximately 100 IOPS per disk for a total of 12000 IOPS. If
> your applications require more than that, you have an I/O issue. SAME or
> Meta will not solve the underlying issue of not enough disks.
>
>
>
> You really need to size your SAN these days based on I/O's per second
> (IOPS) not space. The disks are getting larger, but not necessarily
> faster. Check to make sure your cache is turned on. I have seen huge
> performance hits from the Clariion cache being disabled.
>
>
>
> If you have a symetrix, everything is a slice across all disks in the
> box. That is just the way it works. Of course you have a much larger cache
> with the Sym too, but that's another discussion in itself.
>
>
>
> I hope this helps,
>
> Bryan
>
>
>
> Bryan Thomas
>
> Senior Consultant and Practice Manager
>
> Performance Tuning Corporation
>
> www.perftuning.com
>
>
>
>
> ------------------------------
>
> *From:* oracle-l-bounce_at_freelists.org [mailto:
> oracle-l-bounce_at_freelists.org] *On Behalf Of *amonte
> *Sent:* Thursday, February 01, 2007 2:52 PM
> *To:* oracle-l_at_freelists.org
> *Subject:* How many of you use S.A.M.E?
>
>
>
> Hi
>
>
>
> Anyone here use Stripe.All.Mirror.Everything methology? The one claimed by
> Mr Loaiza 6 years ago?
>
>
>
> Not long ago I posted to list several I/O problems I have with Storage. I
> was told yesterday that the EMC we have is using Meta Devices, some sort of
> SAME. I was told by the EMC guy that the SAN has 120 disks with RAID 1+0,
> 256GB disks. In the factory it is configured with a internal stripe, 256GB
> disk is divided into slices of 8GB. So we have 120 disks each disk with 32
> slices.
>
>
>
> With that configuration you take slices from several physical disks to
> form LUNs. He syas that this is what they call Mete Devices and usually they
> do that only when the customer is in a hurry and needs the disks badly and
> dont have time to make a better planning. He further said that this sort of
> configuration he has seen response times of over 120ms and it is not
> unusual. The porblem with our disks is that sometimes we get like 80ms
> responsetime and most of time beteen 25 and 60.
>
>
>
> I wonder, is Mete Device a SAME configuration? Sure it is deadly easy to
> configure and maintain but then we are suffering performance problems. The
> EMC box is used by over 10 databases, from OLTP to DWH and some of them
> Hybrid configuration. So the chance that a disk is used by all 10 databases
> is quite easy. Wont the disk head go crazy when 10 databases is asking for
> data in several sectors in the same disk? May the chance of that is quite
> small however I would not be surprised that a disk is being used by 3, 4
> databases concurrently.
>
>
>
> TIA
>
>
>
> Alex
>
>
>

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Received on Thu Feb 01 2007 - 17:45:12 CST

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