linux-ext4 - Re: sparsify - utility to punch out blocks of 0s in a file

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Date:	Sun, 5 Feb 2012 20:35:44 +0530
From:	Raghavendra D Prabhu <raghu.prabhu13@...il.com>
To:	Eric Sandeen <sandeen@...hat.com>
Cc:	ext4 development <linux-ext4@...r.kernel.org>,
	xfs-oss <xfs@....sgi.com>
Subject: Re: sparsify - utility to punch out blocks of 0s in a file

Hi,


* On Sat, Feb 04, 2012 at 02:10:30PM -0600, Eric Sandeen <sandeen@...hat.com> wrote:
>On 2/4/12 2:04 PM, Eric Sandeen wrote:
>> Now that ext4, xfs, & ocfs2 can support punch hole, a tool to
>> "re-sparsify" a file by punching out ranges of 0s might be in order.
>
>Gah, of course I sent the version with the actual hole punch commented out ;)
>Try this one.
>
>[root@...de sparsify]# ./sparsify -v fsfile
>blocksize is 4096
>orig start/end 0/536870912/0
>new start/end/min 0/536870912/4096
>punching out holes of minimum size 4096 in range 0-536870912
>punching at 16384 len 16384
>punching at 49152 len 134168576
>punching at 134234112 len 134201344
>punching at 268455936 len 134197248
>punching at 402669568 len 134201344
>[root@...de sparsify]#
>
>Hm but something is weird, right after the punch-out xfs says
>it uses 84K:
>
>[root@...de sparsify]# du -hc fsfile
>84K	fsfile
>84K	total
>
>but then after an xfs_repair it looks saner:
># du -hc fsfile
>4.8M	fsfile
>4.8M	total
>
>something to look into I guess... weird.
>
>
>
>
>_______________________________________________
>xfs mailing list
>xfs@....sgi.com
>http://oss.sgi.com/mailman/listinfo/xfs


So I tried with both resparsify and with cp --sparse, the results 
before xfs_repair looks different (5 extents vs 1) but after that 
it looks similar (5 extents vs 4)


Regards,
-- 
Raghavendra Prabhu
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