On 07/28/2012 02:59 AM, Vladimir Bashkirtsev wrote:
Hello, I am working on optimization of ceph performance: CPU load vs OSD data load. Right now I have 576 PGs in total. Three pools: metadata, data, rbd. Each pool has 192 PGs. data is not used heavily, rbd is in heavy use. In total 6 OSDs in cluster. I have read recommendation about 100 PGs per OSD. Roughly I do have 100 PGs per OSD. But now it seems that PGs in data pool are mostly empty while PGs in rbd pool are quite busy. Would it make sense to increase number of PGs to be 100 per rbd pool per OSD? Technically it should take some memory and CPU but because other two pools are virtually stand still it should not make big difference while improving data placement on OSDs (which is currently somewhat skewed).
If you're not using them, you can delete the data and metadata pools. You can always recreate them later, or use different pools for cephfs.
So here two questions: 1. Should I increase number of PGs in rbd pool or better leave it where it is?
It would be better to increase it from a data balancing point of view, but it's not clear that it would help performance.
2. Wiki says that increase in PGs is not tested and only should be attempted on empty pool. Date on Wiki is quite old. Is this still an issue? Is it safe to increase PGs number on 0.49 on pool in use?
Right now the number of pgs in a pool can't be increased. This should be possible in a couple months. If you can stop I/O to the current pool, you can create a new one with more pgs, copy all the data to it, delete the original and rename the new one. Josh
Regards, Vladimir
-- To unsubscribe from this list: send the line "unsubscribe ceph-devel" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
