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.
On Sat, Apr 29, 2017, 9:46 PM Babu Shanmugam <babu@xxxxxxxx> 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)
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="">
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
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