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@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@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@redhat.com >> https://www.redhat.com/mailman/listinfo/linux-lvm >> read the LVM HOW-TO at http://tldp.org/HOWTO/LVM-HOWTO/ _______________________________________________ linux-lvm mailing list linux-lvm@redhat.com https://www.redhat.com/mailman/listinfo/linux-lvm read the LVM HOW-TO at http://tldp.org/HOWTO/LVM-HOWTO/
