Subject: Re: nfs tuninng with raid
To: Greg Oster <>
From: Brian Hechinger <>
List: current-users
Date: 07/10/2001 23:59:21
On Tue, Jul 10, 2001 at 09:23:35PM -0600, Greg Oster wrote:
> So for a given 8K read you're going to be reading from 1 or 2 disks.
> For a given 8K write, you're going to be reading from 2 or 3 disks, 
> and writing to 2 or 3 disks.  However: with a single RAID 5 set with 15 disks 
> with a stripe width of 63 sectors, you're never going to get the 882 blocks
> required to be able to do a 'full stripe write' (the most efficient write.)
> With a width of 16, you could *guarantee* to never read from more than one 
> disk for a regular block read, and never read and write more than 2 disks for 
> a regular block write.  Depending on what local IO you have, a width of 32 
> might even be better.  Of course this completely ignores updating file access 
> times and updating other metadata, which is going to make performance for 
> random file access of smallish files even worse :-/

i think it would probably be a wise idea for him to consider breaking this
thing up into two or three volumes.  i don't know how realistic that is, but
it's definitely not a bad idea.