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Re: XFS with nfs over rdma performance

To: Samuel Kvasnica <samuel.kvasnica@xxxxxxxxx>
Subject: Re: XFS with nfs over rdma performance
From: Emmanuel Florac <eflorac@xxxxxxxxxxxxxx>
Date: Tue, 22 Jan 2013 14:42:55 +0100
Cc: xfs@xxxxxxxxxxx
Delivered-to: xfs@xxxxxxxxxxx
In-reply-to: <50FE8B33.3060208@xxxxxxxxx>
Organization: Intellique
References: <50FE73A4.7020308@xxxxxxxxx> <20130122123926.3e618de2@xxxxxxxxxxxxxxxxxxxx> <50FE8B33.3060208@xxxxxxxxx>
Le Tue, 22 Jan 2013 13:50:59 +0100
Samuel Kvasnica <samuel.kvasnica@xxxxxxxxx> écrivait:

> Actually, funny way, noalign is always better that sw/su alignment for
> any hardware-RAID I tried so far.

It may be because of lvm in case you're using it.

> But I do not think that mkfs or mount is that much relevant here as
> the local filesystem performance is pretty Ok (actually same as raw
> dd).
> 
> The bottleneck issue comes only when exported by NFS over RDMA. And it
> seems more like a "pumping effect"
> that bottleneck.
> 

NFS tends to make small IOs and can be tricky, in your case it reminds
me of a random access bottleneck, for instance log access. That's why
I'm wondering what iostat output looks like... Periodical log flushing
could be the culprit.

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