My intention is to just identify the root cause for the too much time
spent on a "table create" operation on CephFS. I am *not* trying to
benchmark with my testing. Sorry if it wasn't clear in my mail.
I am sure the time spent would be lesser if I had a proper CEPH setup.
But, I believe even then, the "Table create" operation takes more time
in CephFS than RBD. Please correct me if I am wrong.
On Monday 01 May 2017 08:58 PM, Scottix wrote:
I'm by no means a Ceph expert but I feel this is not a fair
representation of Ceph, I am not saying numbers would be better or
worse. Just the fact I see some major holes that don't represent a
typical Ceph setup.
1 Mon? Most have a minimum of 3
1 OSD? basically all your reads and writes are going to 1 HDD? (I
would say biggest flaw in the benchmark setup)
Is everything on a VM? worse, is it on 1 machine?
What is your network setup?
Why are you testing CephFS and RBD on an older kernel?
Why did you compile from source?
Journal And Data on same disk, is it a spinning drive, SSD, or other?
(We need way more specs to understand)
I would suggest if you want to benchmark you need to get actual
hardware to represent what you would do in production, to try to
maximize the performance of this type of test. Otherwise these numbers
are basically meaningless.
On Sun, Apr 30, 2017 at 9:57 PM Babu Shanmugam <b...@aalam.io
<mailto:b...@aalam.io>> wrote:
On Monday 01 May 2017 10:24 AM, David Turner wrote:
You don't have results that include the added network latency of
having replica 3 replicating across multiple hosts. The reads
would be very similar as the primary is the only thing that is
read from, but writes will not return until after all 3 copies
are written.
I started this as an experiment to see why table creation takes
too much time on CephFS. That was my prime focus, David. So
haven't tried it on pools with size > 1.
On Sat, Apr 29, 2017, 9:46 PM Babu Shanmugam <b...@aalam.io
<mailto:b...@aalam.io>> wrote:
Hi,
I did some basic experiments with mysql and measured the time
taken by a set of operations on CephFS and RBD. The RBD
measurements are taken on a 1GB RBD disk with ext4
filesystem. Following are my observation. The time listed
below are in seconds.
*Plain file system* *CephFS* *RBD*
Mysql install db 7.9 38.3 36.4
Create table 0.43 4.2 2.5
Drop table 0.14 0.21 0.40
Create table + 1000 recs 2.76 4.69 5.07
Create table + 10000 recs
7.69 11.96
Create table + 100K recs
12.06 29.65
From the above numbers, CephFS seems to fare very well while
creating records whereas RBD does well while creating a
table. I tried measuring the syscalls of ceph-osd, ceph-mds
and the mysqld while creating a table on CephFS and RBD.
Following is how the key syscalls of mysqld performed while
creating a table (time includes wait time as well).
*Syscalls of MYSQLD* *CephFS* *RBD*
fsync 338.237 ms 183.697 ms
fdatasync 75.635 ms 96.359 ms
io_submit 50 us 151 us
open 2266 us 61 us
close 1186 us 33 us
write 115 us 51 us
From the above numbers, open, close and fsync syscalls take
too much time on CephFs as compared to RBD.
Sysbench results are below;
*Sysbence 100K records in 60 secs* *CephFS* *RBD*
Read Queries performed 631876 501690
Other Queries performed 90268 71670
No. of transactions 45134 35835
No. of transactions per sec 752.04 597.17
R/W requests per sec 10528.55 8360.37
Other operations per sec 1504.08 1194.34
Above numbers seems to indicate the CephFS does very well
with MYSQL transactions, better than RBD.
Following is my setup;
Num MONs : 1
Num OSDs : 1
Num MDSs : 1
Disk : 10 GB Qemu disk file (Both journal and
data in the same disk)
Ceph version : 10.2.5 (Built from source)
<http://download.ceph.com/tarballs/ceph-10.2.5.tar.gz>
Build config : ./configure --without-debug --without-fuse
--with-libaio \
--without-libatomic-ops --without-hadoop --with-nss
--without-cryptopp \
--without-gtk2 --disable-static --with-jemalloc \
--without-libzfs --without-lttng --without-babeltrace \
--with-eventfd --with-python -without-kinetic
--without-librocksdb \
--without-openldap \
CFLAGS="-g -O2 -fPIC" CXXFLAGS="-g -O2 -std=c++11 -fPIC
Ceph conf : Apart from host and network settings nothing else
is configured
CephFS mount options: rw,relatime,name=cephfs,secret=<hidden>,acl
RBD mount options: rw,relatime,stripe=1024,data=ordered
All the processes were run in a Qemu virtual machine with
Linux 4.4.18 kernel
Searching for "Mysql on CephFS" in google does not give any
useful results. If this kind of experiments had been done
previously and shared publicly, kindly share a link to it.
If you are aware of anything that I can do to optimise this,
kindly let me know. I am willing to continue this experiment
to see how well we can optimise CephFs for mysql.
Thank you,
Babu Shanmugam
www.aalam.io <https://www.aalam.io>
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