Question regarding xfs_repair / memory requirement.

Question regarding xfs_repair / memory requirement.

[Justin Piszcz]

Hi,

I am looking at FS to use for a possible 43TB array.
If there is a problem with a volume this large, how much ram will 
xfs_repair need to fsck the volume?

Justin.

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Re: Question regarding xfs_repair / memory requirement.

[Emmanuel Florac]

Le Mon, 20 Dec 2010 05:20:18 -0500 (EST) vous écriviez:

> I am looking at FS to use for a possible 43TB array.
> If there is a problem with a volume this large, how much ram will 
> xfs_repair need to fsck the volume?
> 

Nothing special, I have tens of such filesystems. With a < 3.0 xfs_progs
you should be able to run xfs_repair with 8 GB of RAM. With newer
versions the memory requirement are even lower.

I often needed at times to run older xfs_repair on big filesystems with
only 1 GB of RAM, and using lots of swap (3, 4 GB or more) did the
trick, though of course it was slow as a caterpillar swimming in
molasses.

-- 
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Emmanuel Florac     |   Direction technique
                    |   Intellique
                    |	<eflorac@intellique.com>
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Re: Question regarding xfs_repair / memory requirement.

[Dave Chinner]

On Mon, Dec 20, 2010 at 05:20:18AM -0500, Justin Piszcz wrote:
> Hi,
> 
> I am looking at FS to use for a possible 43TB array.
> If there is a problem with a volume this large, how much ram will
> xfs_repair need to fsck the volume?

$ dd if=/dev/zero of=/mnt/scratch/test.img bs=1048576 count=1 seek=50000000
1+0 records in
1+0 records out
1048576 bytes (1.0 MB) copied, 0.00463602 s, 226 MB/s
$ ls -lh /mnt/scratch/test.img 
-rw-r--r-- 1 dave dave 48T Dec 21 09:22 /mnt/scratch/test.img
$ sudo mkfs.xfs -d name=/mnt/scratch/test.img,file,size=43t
[sudo] password for dave: 
meta-data=/mnt/scratch/test.img  isize=256    agcount=43, agsize=268435455 blks
         =                       sectsz=512   attr=2
data     =                       bsize=4096   blocks=11542724565, imaxpct=5
         =                       sunit=0      swidth=0 blks
naming   =version 2              bsize=4096   ascii-ci=0
log      =internal log           bsize=4096   blocks=521728, version=2
         =                       sectsz=512   sunit=0 blks, lazy-count=1
realtime =none                   extsz=4096   blocks=0, rtextents=0
$ sudo xfs_repair -m 1 -vv /mnt/scratch/test.img 
Phase 1 - find and verify superblock...
        - max_mem = 1024, icount = 64, imem = 0, dblock = 11542724565, dmem = 5636095
Required memory for repair is greater that the maximum specified with the -m option. Please increase it to at least 5552
$

Not taking inodes into account, you'll need at least 5.5GB of RAM to run
xfs_repair on a 43TB filesystem.

Cheers,

Dave.
-- 
Dave Chinner
david@fromorbit.com

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