[linux-lvm] Thin Pool Performance

[shankha]

Chunk size for lvm was 64K.
Thanks
Shankha Banerjee


On Wed, Apr 20, 2016 at 11:55 AM, shankha <shankhabanerjee at gmail.com> wrote:
> I am sorry. I forgot to post the workload.
>
> The fio benchmark configuration.
>
> [zipf write]
> direct=1
> rw=randrw
> ioengine=libaio
> group_reporting
> rwmixread=0
> bs=4k
> iodepth=32
> numjobs=8
> runtime=3600
> random_distribution=zipf:1.8
> Thanks
> Shankha Banerjee
>
>
> On Wed, Apr 20, 2016 at 9:34 AM, shankha <shankhabanerjee at gmail.com> wrote:
>> Hi,
>> I had just one thin logical volume and running fio benchmarks. I tried
>> having the metadata on a raid0. There was minimal increase in
>> performance. I had thin pool zeroing switched on. If I switch off
>> thin pool zeroing initial allocations were faster but the final
>> numbers are almost similar. The size of the thin poll metadata LV was
>> 16 GB.
>> Thanks
>> Shankha Banerjee
>>
>>
>> On Tue, Apr 19, 2016 at 4:11 AM, Zdenek Kabelac <zkabelac at redhat.com> wrote:
>>> 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
>>>
>>> _______________________________________________
>>> linux-lvm mailing list
>>> linux-lvm at redhat.com
>>> https://www.redhat.com/mailman/listinfo/linux-lvm
>>> read the LVM HOW-TO at http://tldp.org/HOWTO/LVM-HOWTO/