Notice for instance a comparison of random 512k writes between
filestore, newstore with no overlay, and newstore with 8m overlay:
http://nhm.ceph.com/newstore/20150409/filestore/RBD_00524288_randwrite.png
http://nhm.ceph.com/newstore/20150409/8m_overlay/RBD_00524288_randwrite.png
http://nhm.ceph.com/newstore/20150409/no_overlay/RBD_00524288_randwrite.png
The client rbd throughput as reported by fio is:
filestore: 20.44MB/s
newstore+no_overlay: 4.35MB/s
newstore+8m_overlay: 3.86MB/s
But notice that in the graphs, we see very different behaviors on disk.
Filestore does a lot of reads and writes to a couple of specific
portions of the device and has peaks/valleys when data gets written out
in bulk. I would have expected to see more sequential looking writes
during the peaks due to journal writes and no reads to that portion of
the disk, but it seems murkier to me than that.
http://nhm.ceph.com/newstore/20150409/filestore/RBD_00524288_randwrite_OSD0.mpg
newstore+no_overlay does kind of a flurry of random IO and looks like
it's somewhat seek bound. It's very consistent but actual write
performance is low compared to what blktrace reports as the data hitting
the disk. Something happening toward the beginning of the drive too.
http://nhm.ceph.com/newstore/20150409/no_overlay/RBD_00524288_randwrite_OSD0.mpg
newstore+8m overlay is interesting. Lots of data gets written out to
the disk in seemingly large chunks but the actual throughput as reported
by the client is very slow. I assume there's tons of write
amplification happening as rocksdb moves the 512k objects around into
different levels.
http://nhm.ceph.com/newstore/20150409/8m_overlay/RBD_00524288_randwrite_OSD0.mpg
Mark
On 04/10/2015 02:41 PM, Mark Nelson wrote:
Seekwatcher movies and graphs finally finished generating for all of the
tests:
http://nhm.ceph.com/newstore/20150409/
Mark
On 04/10/2015 10:53 AM, Mark Nelson wrote:
Test results attached for different overlay settings at various IO sizes
for writes and random writes. Basically it looks like as we increase
the overlay size it changes the curve. So far we're still not doing as
good as the filestore (co-located journal) though.
I imagine the WAL probably does play a big part here.
Mark
On 04/10/2015 10:28 AM, Sage Weil wrote:
On Fri, 10 Apr 2015, Ning Yao wrote:
KV store introduces too much write amplification, we may need
self-implemented WAL?
What we really want is to hint to the kv store that these keys (or this
key range) is short-lived and should never get compacted. And/or, we
need
to just make sure the wal is sufficiently large so that in practice that
never happens to those keys.
Putting them outside the kv store means an additional seek/sync for
disks,
which defeats most of the purpose. Maybe it makes sense for flash...
but
the above avoids the problem in either case.
I think we should target rocksdb for our initial tuning attempts. So
far
all I've done is played a bit with the file size (1mb -> 4mb -> 8mb)
but my ad hoc tests didn't see much difference.
sage
Regards
Ning Yao
2015-04-10 14:11 GMT+08:00 Duan, Jiangang <jiangang.duan@xxxxxxxxx>:
IMHO, the newstore performance depends so much on KV store
performance due to the WAL - so pick up the right KV or tune it
will be the 1st step to do.
-jiangang
-----Original Message-----
From: ceph-devel-owner@xxxxxxxxxxxxxxx
[mailto:ceph-devel-owner@xxxxxxxxxxxxxxx] On Behalf Of Mark Nelson
Sent: Friday, April 10, 2015 1:01 AM
To: Sage Weil
Cc: ceph-devel
Subject: Re: Initial newstore vs filestore results
On 04/08/2015 10:19 PM, Mark Nelson wrote:
On 04/07/2015 09:58 PM, Sage Weil wrote:
What would be very interesting would be to see the 4KB performance
with the defaults (newstore overlay max = 32) vs overlays disabled
(newstore overlay max = 0) and see if/how much it is helping.
And here we go. 1 OSD, 1X replication. 16GB RBD volume.
4MB write read randw randr
default overlay 36.13 106.61 34.49 92.69
no overlay 36.29 105.61 34.49 93.55
128KB write read randw randr
default overlay 1.71 97.90 1.65 25.79
no overlay 1.72 97.80 1.66 25.78
4KB write read randw randr
default overlay 0.40 61.88 1.29 1.11
no overlay 0.05 61.26 0.05 1.10
Update this morning. Also ran filestore tests for comparison. Next
we'll look at how tweaking the overlay for different IO sizes
affects things. IE the overlay threshold is 64k right now and it
appears that 128K write IOs for instance are quite a bit worse with
newstore currently than with filestore. Sage also just committed
changes that will allow overlay writes during append/create which
may help improve small IO write performance as well in some cases.
4MB write read randw randr
default overlay 36.13 106.61 34.49 92.69
no overlay 36.29 105.61 34.49 93.55
filestore 36.17 84.59 34.11 79.85
128KB write read randw randr
default overlay 1.71 97.90 1.65 25.79
no overlay 1.72 97.80 1.66 25.78
filestore 27.15 79.91 8.77 19.00
4KB write read randw randr
default overlay 0.40 61.88 1.29 1.11
no overlay 0.05 61.26 0.05 1.10
filestore 4.14 56.30 0.42 0.76
Seekwatcher movies and graphs available here:
http://nhm.ceph.com/newstore/20150408/
Note for instance the very interesting blktrace patterns for 4K
random writes on the OSD in each case:
http://nhm.ceph.com/newstore/20150408/filestore/RBD_00004096_randwrite.png
http://nhm.ceph.com/newstore/20150408/default_overlay/RBD_00004096_randwrite.png
http://nhm.ceph.com/newstore/20150408/no_overlay/RBD_00004096_randwrite.png
Mark
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