Dne 19.4.2016 v 03:05 shankha napsal(a):
Hi,
Please allow me to describe our setup.
1) 8 SSDS with a raid5 on top of it. Let us call the raid device : dev_raid5
2) We create a Volume Group on dev_raid5
3) We create a thin pool occupying 100% of the volume group.
We performed some experiments.
Our random write operations dropped by half and there was significant
reduction for
other operations(sequential read, sequential write, random reads) as
well compared to native raid5
If you wish I can share the data with you.
We then changed our configuration from one POOL to 4 POOLS and were able to
get back to 80% of the performance (compared to native raid5).
To us it seems that the lvm metadata operations are the bottleneck.
Do you have any suggestions on how to get back the performance with lvm ?
LVM version: 2.02.130(2)-RHEL7 (2015-12-01)
Library version: 1.02.107-RHEL7 (2015-12-01)
Hi
Thanks for playing with thin-pool, however your report is largely incomplete.
We do not see you actual VG setup.
Please attach 'vgs/lvs' i.e. thin-pool zeroing (if you don't need it keep it
disabled), chunk size (use bigger chunks if you do not need snapshots), number
of simultaneously active thin volumes in single thin-pool (running hundreds of
loaded thinLV is going to loose battle on locking) , size of thin pool
metadata LV - is this LV located on separate device (you should not use RAID5
with metatadata)
and what kind of workload you try on ?
Regards
Zdenek
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