From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from [10.34.131.9] (dhcp131-9.brq.redhat.com [10.34.131.9]) by int-mx11.intmail.prod.int.phx2.redhat.com (8.14.4/8.14.4) with ESMTP id u3J8BRb9003723 for ; Tue, 19 Apr 2016 04:11:27 -0400 References: From: Zdenek Kabelac Message-ID: <5715E82D.1070300@redhat.com> Date: Tue, 19 Apr 2016 10:11:25 +0200 MIME-Version: 1.0 In-Reply-To: Content-Transfer-Encoding: 7bit Subject: Re: [linux-lvm] Thin Pool Performance Reply-To: LVM general discussion and development List-Id: LVM general discussion and development List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , List-Id: Content-Type: text/plain; charset="us-ascii"; format="flowed" To: linux-lvm@redhat.com 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