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Re: synchronization of XFS

To: Steve Lord <lord@xxxxxxx>
Subject: Re: synchronization of XFS
From: Stefan Smietanowski <stesmi@xxxxxxxxxx>
Date: Fri, 26 Mar 2004 00:06:06 +0100
Cc: Christoph Hellwig <hch@xxxxxxxxxxxxx>, Chris Wedgwood <cw@xxxxxxxx>, "IKARASHI, Seiichi" <ikarashi@xxxxxxxxxxxxxxxx>, linux-xfs@xxxxxxxxxxx
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Hi Steve.

>> Yup. That's what's happening. It first does one run with --just-copy
>> where it writes the files using the filesystem then reads the same
>> files using the blockdevice and it's own filesystem code basically.
>>
>> // Stefan
>>
> 
> And I presume the files are missing?
> 
> The bizzare part of this is that if you read the via the block
> device interface, you are looking at the same in memory pages
> which xfs uses for the metadata cache. So even if the data has
> not hit disk yet, things such as names in directories should
> be visible in the metadata cache. Inodes may be more tricky,
> since flushing of inodes into the metadata cache is delayed.
> 
> Try this for an experiment, before the run, set
> 
> /proc/sys/fs/xfs/sync_interval
> 
> down to some small number like 1000, pause for a couple
> of seconds after calling sync, and then see if grub
> can see the files via the block device.
> 
> This tunable controls how long xfs delays writing out
> inodes into the metadata cache from their internal format.

Alright. I'll try that on my DVD in a few hours and get back to you.

Just to verify to be accurate : That /proc entry exists regardless of
if xfs is statically compiled or as a module, correct? (ATRPMS makes
it a module).

// Stefan


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