[Lustre-discuss] lfs_migrate for rebalancing

Andrus, Brian Contractor bdandrus at nps.edu
Sat Jul 16 09:30:45 PDT 2011


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 at 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 at compute-3-1 ps2]# lfs_migrate -y PS01-071.xml
PS01-071.xml: done
[root at 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 at compute-3-1 ps2]# cp PS01-071.xml PS01-071.xml.tmp
[root at 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 at 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

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