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Re: XFS memory recomendation?

To: "Assarsson, Emil" <Emil.Assarsson@xxxxxxxxxxxxxxxx>
Subject: Re: XFS memory recomendation?
From: Dave Chinner <david@xxxxxxxxxxxxx>
Date: Fri, 17 Feb 2012 13:49:41 +1100
Cc: "xfs@xxxxxxxxxxx" <xfs@xxxxxxxxxxx>
In-reply-to: <2BF070A7A2375D46BA1B6087F8D5DCB68BEA721CA3@xxxxxxxxxxxxxxxxxxxxxxx>
References: <2BF070A7A2375D46BA1B6087F8D5DCB68BEA721CA3@xxxxxxxxxxxxxxxxxxxxxxx>
User-agent: Mutt/1.5.21 (2010-09-15)
On Thu, Feb 16, 2012 at 12:50:57PM +0100, Assarsson, Emil wrote:
> Hi,
> 
> Are there any recommendations about how much memory I need based
> on the size of the file system and/or amount of files?  For
> example: how much memory would be optimal for a 20TB file system
> with 3000000 files? 

/me shrugs

> I guess it depends on the usage pattern?

Totally.

> Is there any way to make sure that the file allocation table stays in the 
> memory?

What's a "file allocation table"? XFS doesn't have one. :)

XFS does have a sophisticated metadata cache and reclaim scheme that
keeps frequently referenced metadata hot in cache, but you as a
user have very little control over that because the cache size is
effectively controlled by memory pressure. i.e. it's size is
completely workload dependent.....

Cheers,

Dave.
-- 
Dave Chinner
david@xxxxxxxxxxxxx

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