[Lustre-discuss] lfs_migrate for rebalancing

[Andrus, Brian Contractor]

All,

 

Am I incorrect in the way I read that lfs_migrate can be used to rebalance  a filesystem after adding OSTs?

 

Here is some output on a 22M file that was all on one OST and we now have 9:

 

[root@compute-3-1 ps2]# lfs getstripe PS01-071.xml

PS01-071.xml

lmm_stripe_count:   1

lmm_stripe_size:    1048576

lmm_stripe_offset:  6

        obdidx           objid          objid            group

             6         4411098       0x434eda                0

 

[root@compute-3-1 ps2]# lfs_migrate -y PS01-071.xml

PS01-071.xml: done

[root@compute-3-1 ps2]# lfs getstripe PS01-071.xml

PS01-071.xml

lmm_stripe_count:   1

lmm_stripe_size:    1048576

lmm_stripe_offset:  4

        obdidx           objid          objid            group

             4        50856625      0x30802b1                0

 

[root@compute-3-1 ps2]# cp PS01-071.xml PS01-071.xml.tmp

[root@compute-3-1 ps2]# lfs getstripe PS01-071.xml.tmp

PS01-071.xml.tmp

lmm_stripe_count:   9

lmm_stripe_size:    1048576

lmm_stripe_offset:  2

        obdidx           objid          objid            group

             2        73524719      0x461e5ef                0

             5         4389362       0x42f9f2                0

             3        53566843      0x3315d7b                0

             0        47139754      0x2cf4baa                0

             6         4411100       0x434edc                0

             1        56746451      0x361e1d3                0

             8         4416089       0x436259                0

             7         4411127       0x434ef7                0

             4        50856626      0x30802b2                0

 

[root@compute-3-1 ps2]#

 

So it moved the file to another OST, but left the strip count as 1.

But when I cp’ed the file, it properly striped it across all the OSTs.

 

This doesn’t seem all that useful for rebalancing.

 

Brian Andrus

ITACS/Research Computing

Naval Postgraduate School

Monterey, California

voice: 831-656-6238

 

[Sebastien Piechurski]

Hi,

 

lfs_migrate will rebalance space usage across the OSTs of your filesystem by copying files and deleting the original ones on the most empty OSTs. It will not change stripe count of files. You have to migrate lots of files to see the new balance. This is why you don't see the usefulness with only one file.

lfs_migrate also accepts options to specify which OSTs you want to redistribute.

 

Sebastien.

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From: lustre-disc...@lists.lustre.org [mailto:lustre-disc...@lists.lustre.org] On Behalf Of Andrus, Brian Contractor
Sent: samedi 16 juillet 2011 18:31
To: lustre-...@lists.lustre.org
Subject: [Lustre-discuss] lfs_migrate for rebalancing