Hi Allen,
On a somewhat related note, I wanted to mention that I had forgotten
that chhabaremesh's min_alloc_size commit for different media types was
committed into master:
https://github.com/ceph/ceph/commit/8185f2d356911274ca679614611dc335e3efd187
IE those tests appear to already have been using a 4K min alloc size due
to non-rotational NVMe media. I went back and verified that explicitly
changing the min_alloc size (in fact all of them to be sure) to 4k does
not change the behavior from graphs I showed yesterday. The rocksdb
compaction stalls due to excessive reads appear (at least on the
surface) to be due to metadata traffic during heavy small random writes.
Mark
On 06/08/2016 06:52 PM, Allen Samuels wrote:
Let's make a patch that creates actual Ceph parameters for these things so that we don't have to edit the source code in the future.
Allen Samuels
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-----Original Message-----
From: ceph-devel-owner@xxxxxxxxxxxxxxx [mailto:ceph-devel-
owner@xxxxxxxxxxxxxxx] On Behalf Of Manavalan Krishnan
Sent: Wednesday, June 08, 2016 3:10 PM
To: Mark Nelson <mnelson@xxxxxxxxxx>; Ceph Development <ceph-
devel@xxxxxxxxxxxxxxx>
Subject: RocksDB tuning
Hi Mark
Here are the tunings that we used to avoid the IOPs choppiness caused by
rocksdb compaction.
We need to add the following options in src/kv/RocksDBStore.cc before
rocksdb::DB::Open in RocksDBStore::do_open opt.IncreaseParallelism(16);
opt.OptimizeLevelStyleCompaction(512 * 1024 * 1024);
Thanks
Mana
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