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Re: XFS: Abysmal write performance because of excessive seeking (allocat

To: Stefan Ring <stefanrin@xxxxxxxxx>
Subject: Re: XFS: Abysmal write performance because of excessive seeking (allocation groups to blame?)
From: Emmanuel Florac <eflorac@xxxxxxxxxxxxxx>
Date: Sat, 7 Apr 2012 10:53:18 +0200
Cc: stan@xxxxxxxxxxxxxxxxx, Linux fs XFS <xfs@xxxxxxxxxxx>
In-reply-to: <CAAxjCEyJW1b4dbKctbrgdWjykQt8Hb4Sw1RKdys3oUsehNHCcQ@xxxxxxxxxxxxxx>
Organization: Intellique
References: <CAAxjCEwBMbd0x7WQmFELM8JyFu6Kv_b+KDe3XFqJE6shfSAfyQ@xxxxxxxxxxxxxx> <20350.9643.379841.771496@xxxxxxxxxxxxxxxxxx> <20350.13616.901974.523140@xxxxxxxxxxxxxxxxxx> <CAAxjCEzkemiYin4KYZX62Ei6QLUFbgZESdwS8krBy0dSqOn6aA@xxxxxxxxxxxxxx> <4F7F7C25.8040605@xxxxxxxxxxxxxxxxx> <CAAxjCEyJW1b4dbKctbrgdWjykQt8Hb4Sw1RKdys3oUsehNHCcQ@xxxxxxxxxxxxxx>
Le Sat, 7 Apr 2012 09:27:50 +0200 vous écriviez:

> So it sounds like that for poor guys like us, who can’t afford the
> hardware to have dozens of spindles, the best option would be to
> create the XFS file system with agcount=1? That seems to be the only
> reasonable conclusion to me, since a single RAID device, like a single
> disk, cannot write in parallel anyway.

You best option is to buy a SSD. Seriously, even a basic decent consumer
model will bury your array in the dust. Also, recent RAID controllers
from LSI and Adaptec are able to "enhance" a spinning rust array by
using an SSD as a cache.

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