[Top] [All Lists]

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

To: Linux fs XFS <xfs@xxxxxxxxxxx>
Subject: Re: XFS: Abysmal write performance because of excessive seeking (allocation groups to blame?)
From: Stefan Ring <stefanrin@xxxxxxxxx>
Date: Tue, 10 Apr 2012 17:56:57 +0200
Dkim-signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20120113; h=mime-version:in-reply-to:references:date:message-id:subject:from:to :content-type:content-transfer-encoding; bh=ZLhC4hFmThcqIHe5NDTtTnVlaBgbyOXLsK8CzTjeguo=; b=OkTO7RG/trsgW1IdEWyL+4reVht4NvCOzzX3q1mkJYXb6mZvkJUE82onTUMzKOeVzV H74el1RX4O3ZQU2tGWpnEizBS2OngLTW5dNONFHXds24BH1uDhEbMrF9o9nYKrLnmmgr M3FEX59jS276v1VGwoZMUXzIQXO6do4qZ2iR1TFQQlBYVNGmEAq5RNIyaUL8FfAkifrS RyQ27ATqTxsaTJQj31PMP0+RkaYwL4kFUgfccgGSbdCtf+7nIaLQUbBzu2uClPhnTPHm CCGT2gEqiICyT2DdiWAHCcU5dD1N7I9SlP9Hvb1qm58xswPZANWkib3QpkTrnB36iZBE SIQw==
In-reply-to: <4F844474.3010005@xxxxxxxxx>
References: <CAAxjCEwBMbd0x7WQmFELM8JyFu6Kv_b+KDe3XFqJE6shfSAfyQ@xxxxxxxxxxxxxx> <20120405213740.GA22824@xxxxxxxxxxxxx> <CAAxjCExBcaB6J-u7ivZKWnKiF7oP10JRxzKzQNRuppHkTE2Tzw@xxxxxxxxxxxxxx> <201204072057.38286.Martin@xxxxxxxxxxxx> <CAAxjCEzRa7CpbA9iESEDjmWQMsJTjkWHJj69ADOXDa4CiRpx3w@xxxxxxxxxxxxxx> <4F844474.3010005@xxxxxxxxx>
> try 128k to 512k for stripe size.  And try to increase your agcount by
> (nearly) an order of magnitude.

Would that be of any real value to anyone here, except for satisfying
curiosity (which I feel as well ;))? Because frankly, it’s a lot of
work, and I’m quite through with this tedious kind of activity…

My conclusion is that everything should work well if the levels below
the file system behaved the way they should and brought the writes
into a sane order. Apparently, both the RAID controller as well as the
Linux block scheduler fail to do so. Despite the annoying nature of
this state of affairs, I do believe that file systems should be able
to count on the lower levels of the stack for such low-level work and
not work around them, but apparently, they are often failed. Probably
that’s one of the reasons why almost every file system acquires some
sort of block scheduling over time. Maybe some day, the Linux IO
scheduler will do a better job. Unfortunately, by then, this entire
issue will be irrelevant because nobody will be using rotational
storage anymore, at least not for everyday work.

<Prev in Thread] Current Thread [Next in Thread>