Re: ASM LUN sizes and number of disks

From: Greg Rahn <>
Date: Mon, 10 Nov 2008 14:17:28 -0800
Message-ID: <>

On Mon, Nov 10, 2008 at 1:19 AM, hrishy <> wrote:
> I am still confused (although i do agree with ideas of Greg)
> Is there a paper which describes whats the ideal combination of disks and sik sizes for ASM.

There are many resources here:

> I am using external redundancy should i still be worried about having only 2 disks ?

If you only have 2 disks, the only external redundancy you can have is to mirror them, then they would appear to the host as a single LUN. Sure, you could partition the disks and present that as multiple LUNs but that buys you zero.

> I am planning to add 2 2000Gb disks and then simulatenously drop the
> 6 50Gb disks so rebalance is a single operation

Space is cheap, but spindles are expensive. IOPS and I/O scan rates are proportional to the number of spindles. In your case, by moving from 6 to 2 drives you are cutting down the IOPS and I/O scan rates by a factor of 3, so you are reducing your drive performance in order to add capacity. Be careful...

Greg Rahn
Received on Mon Nov 10 2008 - 16:17:28 CST

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