On 03/12/2013 15:06, Gerald Brandt wrote:
Anybody have an idea whats happened (see below)? The iSCSI and NFS load are
both KVM images (iSCSI is LVM based).
Gerald
----- Original Message -----
From: "Gerald Brandt" <[email protected]>
To: [email protected]
Sent: Saturday, November 30, 2013 11:00:20 AM
Subject: [DRBD-user] DRBD with iSCSI vs NFS issue
Hi,
I've been running DRBD on my servers for quite some time on some
servers at a clients (a little over a year with this client, I
believe). I've been exporting drbd0 as iSCSI for the entire time.
Write tests over GigE (1B block size, sequential write) gives me an
everage of 118MB/s. Very good.
Last week, I switched drbd0 from iSCSI to NFSv3 exports.
Performing the same test (I use XenServer Performance VM tool), I get
very strange behaviour. atop shows an average write speed of ~35
MB/s. The Perf Tool shows 117-118 MB/s, with drops down to 0MB/s.
There are a lot of drops, and the average via the tool equals what
atop shows.
If I remove the secondary, performance via NFS jumps and stays at
117-118 MB/s.
The underlying DRBD config has not changed at all.
Why am I seeing the difference between iSCSI exports on drbd0 vs NFS
exporst on drbd0, only when the secondary is attached?
Gerald
Hi
I have a similar issue (look for my recent post), except my issue causes
load on my nfs clients to climb under lots or read/writes, I have
lowered the impact now by adjusting the nfs mount options. According to
the research I have done the slower speeds of nfs are just the nature of
the nfs server due to it being a "shared" file system where as iscsi is
dedicated to a single hosts read/writes.
Thank you,
Mark Adrian Coetser
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