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List: linux-nfs
Subject: Re: [NFS] nfs performance problem
From: "Matt Heaton" <admin () 0catch ! com>
Date: 2002-11-05 20:46:04
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Cachefs will help quite a lot in my opinion because it doesn't just store
the files in RAM,
it uses the hard drive. So if you have an NFS client with an extra 5 gig
that you can
designate as cache then reads to the NFS server will go down DRAMATICALLY as
it will hit local cache on the NFS clients drive.
I agree raid 1+0 should be much faster for writes and a little for read, but
RAID 5 still
reads from all drives simultaneously (Has to read parity in too I know), but
can read
all 7 drives at once instead of only 4 drives at once in a raid 1+0
configuration with 8 drives
in the array. I have never used 1+0 so I am only talking about physical
drive layout rather
than any personal experience. Are my assumptions correct that raid 5 does
in fact read
from all drives at the same time? If so, reading might be a LITTLE faster
on raid 1+0 than
raid 5, but it shouldn't be HUGE. When I contacted 3ware, they basically
said the same thing.
I do agree that writes are MUCH faster on 1+0 than raid 5.
Any thoughts?
L8r...
Matt
> On Tue, Nov 05, 2002 at 01:22:25PM -0700, Matt Heaton wrote:
> > each NFS server. So even though our throughput of only 1.5 MB isn't
high.
> > The number of files per second is
> > actually quite high, and causes things to slow down because of seek time
> > issues. PLEASE GIVE US CACHEFS SOMEONE??
>
> How is cachefs going to help? The kernel is already trying to cache data
> as much as possible. Once you're trying to serve more data than you have
> RAM, this are naturally going to degreate quite significantly as the
system
> becomes seek bound.
>
> > Does anyone have experience with IDE Raid arrays that get over 250 tps
in
> > iostat that work fine? I would
> > be VERY VERY VERY interested to find out.
>
> Use raid1+0 and you'll be much happier, as read requests will be balanced
> over multiple drives (mirroring means the same data can be read from all
> of the mirrors). Additionally, you'll have much lower CPU utilization
> and writes won't cause all disks in the array to seek for strip updates.
> Read the archives for the past couple of weeks for another example of the
> performance increase when going from raid5 to raid1+0.
>
> -ben
>
>
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