RE: Is my Oracle Server issuing more IO than it can handle

From: Amaral, Rui <>
Date: Tue, 7 Dec 2010 14:32:00 -0500
Message-ID: <1B861F1ABE40A84AA92AD585B20C558B26E4E11D0B_at_EX7T2-CV06.TDBFG.COM>

you said moved to a different storage so a couple of questions come to mind on this:
  1. ask your storage guys how the 2 differ in configuration, ie., RAID types, FC configuration, I/O port sharing ( different db systems sharing the same port can be a problem)
  2. from the OS how the filesystem is configured. Misaligned block sizes between the array and the os filesystem can slow things down (think of it in terms of chained rows and you'll get close to the idea). This applies equally to ASM and regular filesystems
  3. and of course if they can tell if the luns are on the outside of the physical disks or not.

in terms of calculating IOPS use Orion or Bonnie for pure OS throughput and then go from there. Just some thoughts

Rui Amaral
Database Administrator
TD Bank Financial Group
220 Bay St., 11th Floor
Toronto, ON, CA, M5K1A2
(bb) (647) 204-9106

From: [] On Behalf Of Oracle Dba Wannabe Sent: Tuesday, December 07, 2010 2:26 PM To: Harel Safra
Cc: Niall Litchfield;; Subject: Re: Is my Oracle Server issuing more IO than it can handle

No in fact a san is being used which is being shared with other database servers in the environment - so based on what you;ve said the san cache would be shared too. The servers are hp servers connected to an xp san. That said, if this hp server was the only one attached to it - the calculation i used below would then be valid? If not does anyone know how to calculate how many iops are possible from a storage and how much the oracle server is issuing? thanks

From: Harel Safra <> To:
Cc: Niall Litchfield <>;; "" <> Sent: Wed, December 8, 2010 12:12:42 AM
Subject: Re: Is my Oracle Server issuing more IO than it can handle

This calculation is only true if you work with disk drive directly attached to you servers, and even then when there is no cache in the raid controller. Once you start working with central storage systems things like cache size, i/o distribution and disk sharing start to come into play.

For example, our EMC dMX4 storage has 96GB of cache. If your database is smaller than that (and nothing else uses the cache in this example) you could get very high throughput even with a single physical disk.

Do you know which kind of storage you use? Is you system the only system attached to it?

Harel Safra

On 07/12/2010 20:05, Oracle Dba Wannabe wrote: Do any of you have any thoughts w.r.t to question 1 - whether those calculations can be representative of the disks i may need. thanks

  1. Is there someway from awr that I can determine that the Oracle server is issuing more IO than the storage system can handle for example: Physical reads: 954.74 16.68 Physical writes: 418.89 7.32 Phy Reads + Phy Writes = 1372 IOPS Can I then say that if each disk can do 100 IOPS, that the storage system should at least have 13 Disks? (13x100 IOPS)? Or is that an over simplification?

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Received on Tue Dec 07 2010 - 13:32:00 CST

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