Xuechen and I continued this discussion off list and found that varstrip
is not the right tool for the job. It does not control which servers
are used and also does not let you start at an arbitrary strip as I
suggested in the B example.
Right now we don't really have hooks in PVFS to control the layout this
specifically at a directory level.
-Phil
Phil Carns wrote:
Hi Xuechen,
I believe that this is possible with the varstrip distribution in PVFS.
Here is some further information:
http://www.pvfs.org/fisheye/browse/PVFS/doc/pvfs2-tuning.tex?r=1.1.22.1#l328
For example, I think on directory A you would set something like:
setfattr -n user.pvfs2.dist_name -v varstrip_dist A
setfattr -n user.pvfs2.dist_params -v "strips:0:64K;1:64K" A
And this for B:
setfattr -n user.pvfs2.dist_name -v varstrip_dist B
setfattr -n user.pvfs2.dist_params -v "strips:2:64K;3:64K" B
That should automatically set the number of datafiles to 2 based on the
distribution parameters, but it is possible that some previous releases
didn't do that. If you have trouble use these commands to make it
explicit:
setfattr -n user.pvfs2.num_dfiles -v "2" A
setfattr -n user.pvfs2.num_dfiles -v "2" B
A few other misc. pointers:
- this only affects new files in any given directory and does not change
existing files
- make sure to test the results by using "pvfs2-viewdist -f <filename>"
to see how new files are distributed
-Phil
Xuechen Zhang wrote:
There is a question about setting PVFS2 directory attributes. I have
four I/O servers (0-3). I want to locate file A in directory A on
server 0&1 and file B in directory B on server 2&3 by settting stripe
distribution for the two directory. Can I implement this kind of
distribution in PVFS2? If not, any suggestion for that? Thanks.
Xuechen
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