On Thu, 11 Sep 2014, Gregory Farnum wrote: > On Thu, Sep 11, 2014 at 4:13 AM, Kenneth Waegeman > <Kenneth.Waegeman at ugent.be> wrote: > > Hi all, > > > > I am testing the tiering functionality with cephfs. I used a replicated > > cache with an EC data pool, and a replicated metadata pool like this: > > > > > > ceph osd pool create cache 1024 1024 > > ceph osd pool set cache size 2 > > ceph osd pool set cache min_size 1 > > ceph osd erasure-code-profile set profile11 k=8 m=3 > > ruleset-failure-domain=osd > > ceph osd pool create ecdata 128 128 erasure profile11 > > ceph osd tier add ecdata cache > > ceph osd tier cache-mode cache writeback > > ceph osd tier set-overlay ecdata cache > > ceph osd pool set cache hit_set_type bloom > > ceph osd pool set cache hit_set_count 1 > > ceph osd pool set cache hit_set_period 3600 > > ceph osd pool set cache target_max_bytes $((280*1024*1024*1024)) > > ceph osd pool create metadata 128 128 > > ceph osd pool set metadata crush_ruleset 1 # SSD root in crushmap > > ceph fs new ceph_fs metadata cache <-- wrong ? > > > > I started testing with this, and this worked, I could write to it with > > cephfs and the cache was flushing to the ecdata pool as expected. > > But now I notice I made the fs right upon the cache, instead of the > > underlying data pool. I suppose I should have done this: > > > > ceph fs new ceph_fs metadata ecdata > > > > So my question is: Was this wrong and not doing the things I thought it did, > > or was this somehow handled by ceph and didn't it matter I specified the > > cache instead of the data pool? > > Well, it's sort of doing what you want it to. You've told the > filesystem to use the "cache" pool as the location for all of its > data. But RADOS is pushing everything in the "cache" pool down to the > "ecdata" pool. > So it'll work for now as you want. But if in future you wanted to stop > using the caching pool, or switch it out for a different pool > entirely, that wouldn't work (whereas it would if the fs was using > "ecdata"). > > We should perhaps look at prevent use of cache pools like this...hrm... > http://tracker.ceph.com/issues/9435 Should we? I was planning on doing exactly this for my home cluster. sage
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