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Re: file preallocation without unwritten flag being set

To: p v <pvlogin@xxxxxxxxx>
Subject: Re: file preallocation without unwritten flag being set
From: Eric Sandeen <sandeen@xxxxxxxxxxx>
Date: Tue, 12 May 2009 19:04:06 -0500
Cc: xfs@xxxxxxxxxxx
In-reply-to: <283244.29270.qm@xxxxxxxxxxxxxxxxxxxxxxxxxxx>
References: <283244.29270.qm@xxxxxxxxxxxxxxxxxxxxxxxxxxx>
User-agent: Thunderbird (Macintosh/20090302)
p v wrote:
> Hello,
> I need to create large files fast without initializing them - in the
> past I used these steps -
> mkfs -t xfs -f -d unwritten=0 /dev/sda1 mount -t xfs -o noatime
> /dev/sda1 /hay touch /hay/foo xfs_io /hay/foo xfs_io> resvsp 0 1024g 
> xfs_io> quit ls -i /hay/foo 131 /hay/foo umount /hay xfs_db -x
> /dev/sda1 xfs_db> inode 131 xfs_db> write core.size 1099511627776 
> core.size = 1099511627776 xfs_db> q

Is there a reason that you don't want the unwritten flag set?  (You know
that not using the unwritten extents feature exposes garbage from the
disk in this case?)

There may well be a legit reason but I just want to make sure you're
doing what you think you're doing :)


> But unwritten=0 is failing as unrecognized option now (was it
> deprecated????) so I tried to clear the unwritten extent flag
> directly -
> xfs_db> a u.bmbt.ptrs[1] xfs_db> write recs[1].extentflag 0 
> recs[1].extentflag = 1 xfs_db>
> It just won't change to 0 - any way to do this? Or is there any
> straightforward way to preallocate a large file and set it's file
> size without the unwritten flags being turned on?
> Thanks
> Peter Vajgel
> _______________________________________________ xfs mailing list 
> xfs@xxxxxxxxxxx http://oss.sgi.com/mailman/listinfo/xfs

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