I have 65TB stored on 24 OSDs on 3 hosts (8 OSDs per host). SSD journals and spinning disks. Our performance before was acceptable for our purposes - 300+MB/s simultaneous transmit and receive. Now that we're up to about 50% of our total storage capacity (65/120TB, say), the write performance is still ok, but the read performance is unworkable (35MB/s!)
I am using index sharding, with 256 shards. I don't see any CPUs saturated on any host (we are using radosgw by the way, and the load is light there as well). The hard drives don't seem to be *too* busy (a random OSD shows ~10 wa in top). The network's fine, as we were doing much better in terms of speed before we filled up.
Is there anything we can do about this, short of replacing hardware? Is it really a limitation of Ceph that getting 50% full makes your cluster unusable? Index sharding has seemed to not help at all (I did some benchmarking, with 128 shards and then 256; same result each time.)
Or are we out of luck?
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