Read-from-replica does not happen unless you go through some contortions with config and developer setups. However, all n OSDs should be the primary for about 1/n% of the data, so you should be seeing reads to to both OSDs as long as you touch several objects at a time. -Greg
On Wednesday, August 28, 2013, daniel pol wrote: > Hi ! > > I need a little help understanding reads from replicas. I've read a few > conflicting messages and the documentation is not very clear to me on this > subject (maybe I didn't find the proper doc). > Here's the question: With default replication of 2 (size=2), when doing > reads (big sequential reads in my case) are we expecting to see read going > to the "primary" object AND it's replicas ? (similar to RAID1 where you > read from both sides of the mirror) > > I'm not seeing that on my setup right now. I have a pool with 16 PGs on 2 > OSDs. When I do reads only one 1 OSD gets IO. > If that's normal (replica involved in IO only when primary is down) I'll > take a note, otherwise I'll have to find why I don't get reads from > replicas. > > Have a nice day, > Dani > -- Software Engineer #42 @ http://inktank.com | http://ceph.com
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