Ceph - how to check and monitor journaling on SSD

[kyob]

I have journaling on SSD for each SATA drive but how can I:

1. check that journaling on SSD work?
2. monitor utlization,activity,etc. for journaling on SSD?
3. what are the best settings for journaling on SSD when one SATA has one SSD with journaling?
4. how can I measure journaling performance on SSD drives?

 

[udo]

I have journaling on SSD for each SATA drive but how can I:

1. check that journaling on SSD work?
2. monitor utlization,activity,etc. for journaling on SSD?

Hi,
simply look for IO on the journal-SSD.

EG with iostat (package sysstat)

root@ceph-01:~# iostat -dm 10 /dev/sdo /dev/sdn
Linux 3.16.0-0.bpo.4-amd64 (ceph-01)    16.10.2015      _x86_64_        (12 CPU)

Device:            tps    MB_read/s    MB_wrtn/s    MB_read    MB_wrtn
sdn              25,65         0,04         2,10      70888    3998738
sdo              26,41         0,03         1,91      57450    3636715

Device:            tps    MB_read/s    MB_wrtn/s    MB_read    MB_wrtn
sdn              22,90         0,00         0,52          0          5
sdo              13,80         0,00         0,07          0          0

first entry show how much is written since start and every 10 seconds you see how much is written in this time.
You should allmost see no (or onlyvery small) reads, because the content is in the buffer also and written from there to the OSD-

• what are the best settings for journaling on SSD when one SATA has one SSD with journaling?

what do you mean with best settings?

• how can I measure journaling performance on SSD drives?

the yournal performance is your ceph write preformance - if you have an pool named test, you can test with

rados -p test bench 60 write --no-cleanup

Udo