Pool Migration

External documentation

• dcache book: http://www.dcache.org/manuals/Book/cookbook/cb-pool-migration.shtml

Example for copying pool t3fs05_cms to t3fs07_cms using the 'migration copy' command

Set source pool to read only

The dcache book documentation describes setting the pool to readonly by using the pool disable -rdonly command of the pool cell. I noticed that this led to a whole number of stuck transfers, but was not able to analyze the situation adequately. However, one can also set a pool to readonly inside the PoolManager configuration or by using psu set pool rdonly in the PoolManager cell. This only affects the routing of the requests. I prefer to do it in both places!

We have a shelltool for setting the PoolManager pool configuration (as most shelltools, it can take a list of arguments on stdin, therefore the leading echo):

echo  t3fs05_cms | dc_set_pools_readonly.sh -f

Enter the admin shell and switch to the source pool's cell:

[t3se01.psi.ch] (local) admin > cd t3fs05_cms
[t3se01.psi.ch] (t3fs05_cms) pool disable -rdonly

You can check which pools are disabled and which pools are set to readonly, by using

dc_get_pool_list.sh -o d

dc_get_pool_list.sh -o ro

Start the migration

[t3se01.psi.ch] (t3fs05_cms) migration copy t3fs07_cms

You can list the active migrations

[t3se01.psi.ch] (t3fs05_cms) migration ls

This yields 1 for our example

You can check on the progress of the migration

[t3se01.psi.ch] (t3fs05_cms) migration info 1

You can set the number of parallel copy processes to two for our migration job by using

[t3se01.psi.ch] (t3fs05_cms) migration concurrency 1 2

Check whether all files have been migrated

Simple way using the shelltools

Get the contents of both pools

dc_get_rep_ls.sh t3fs05_cms > t3fs05_cms.lst
dc_get_rep_ls.sh t3fs07_cms > t3fs07_cms.lst

Run a simple loop to find the missing entries on the target pool

for n in $(cat t3fs05_cms.lst); do grep -q $n t3fs07_cms.lst; if test $? -ne 0; then echo $n >> missing-on-t3fs07.lst; fi; done

If there are missing entries, use the shelltools to find out more about them, e.g. map to pnfs IDs:

dc_get_pnfsname_from_IDlist.sh missing-on-t3fs07.lst

It may well be that you find that all of these files lack a mapping in pnfs (which can happen if during the migration these entries were deleted by users. Since the source pool is set to read only, the physical file will remain on the disk until the pool is made read/write again).

Remove files on the source pool

dc_rep_rm_list.sh t3fs05_cms.lst t3fs05_cms.lst

Using migration move

Instead of copying the files, checking the correct copying and then removing the source files one can also use the migration move command instead of the migration copy. Then dcache itself will remove the copied source files.

-- DerekFeichtinger - 2010-03-17