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Speed up xfsdump ?

To: linux-xfs@xxxxxxxxxxx
Subject: Speed up xfsdump ?
From: Nicolas Kowalski <Nicolas.Kowalski@xxxxxxx>
Date: Mon, 12 Sep 2005 18:43:39 +0200
Sender: linux-xfs-bounce@xxxxxxxxxxx

I am testing the backup of a new SCSI-attached RAID5 SATA array on a 
SDLT320 tape drive, using xfsdump 2.2.27.

I noticed that xfsdump is "much" slower than tar of cpio, and I would 
like to know if I can do anything to speed up things. 

NB: I used kernels 2.4.31 and, and did not see a noticable 
difference using the one or the other. I tried the ihashsize mount 
option (when using 2.6.x kernel), and approximatively got the same 

1) First, the testbed

The storage is a ~1.5TB array, that I partially filled with the some 
contents of our user homes. The 'df' and 'df -i' commands shows the 

# df /dev/sda1
/dev/sda1            1463454592  29337040 1434117552   3% /raid

# df -i /dev/sda1
Filesystem            Inodes   IUsed   IFree IUse% Mounted on
/dev/sda1            1444198400  526803 1443671597    1% /raid

The filesystem is completely inactive during the tests.

The SDLT320 drive is 25MB/s capable (tested by pulling a big 500MB tar 
file with dd on the tape).

2) The tests

2.a) xfsdump

command used: xfsdump -J - /raid | dd obs=64k of=/dev/nst0

dd shows: 5985202 bytes/sec

I also tested with a 1M blocksize, and did not get a much better number 

2.b) tar

command used: tar cf - /raid | dd obs=64k of=/dev/nst0

dd shows: 16518724 bytes/sec

2.c) cpio

command used: find /raid -xdev -print0 | cpio -0 -H newc -o \
                | dd obs=64k of=/dev/nst0

dd shows: 15911069 bytes/sec

3) Any tips to speed up xfsdump ?


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