On 11/06/2012 11:59 AM, Sage Weil wrote:
When i have one pool with 800 pgs and i add 20 new OSDs how does a new pool
help? I mean the old pools will stay with 800 pgs.
It make the distribution of existing data less coarse, but as the size of
teh PGs for the new pool increases things will tend to level out.
My suggestion is to overshoot the PG count a little bit (not too much!),
maybe ~200 pgs per osd. If things get too unbalanced after a significant
expansion you can put new data is new pools, or make fine-grainted
adjustments in the CRUSH map.
I suspect that this will be sufficient for just about everyone until the
splitting functionality is in place... hopefully in 1-2 dev releases after
bobtail.
Maybe I missed something but do you mean about 100-200 PG's per pool per
OSD or 100-200 PG's per OSD? Because when you create new pools, the PG's
per OSD increases a lot.
Stefan
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