Re: [ovirt-users] Poor iSCSI Performance

Hi all, I've been trying to resolve a storage performance issue but have had no luck in identifying the exact cause. I have my storage domain on iSCSI and I can get the expected performance (limited by the Gbit Ethernet) when running bonnie++ on: * a regular physical machine configured with the iSCSI initiator connected to a dedicated iSCSI test target -- thus oVirt and VM technology are completely out of the picture * my oVirt host with the initiator connected to that same dedicated target -- thus I have an iSCSI connection on the oVirt host but I'm not using the iSCSI connection provided by oVirt's storage domain * a VM (hosted by oVirt) with the initiator (inside the VM) connected to that target -- thus bypassing oVirt's storage domain and the virtual disk it provides this VM However, if I just use a regular virtual disk via oVirt's storage domain the performance is much worse. I've tried both VirtIO and VirtIO-SCSI and have found no appreciable difference. Here's a typical example of the poor performance I get (as tested with bonnie++) with the normal virtual disk setup: # bonnie++ -d . -r 2048 -u root:root <snip> Version 1.96 ------Sequential Output------ --Sequential Input- --Random- Concurrency 1 -Per Chr- --Block-- -Rewrite- -Per Chr- --Block-- --Seeks-- Machine Size K/sec %CP K/sec %CP K/sec %CP K/sec %CP K/sec %CP /sec %CP narvi-f21.double 4G 806 91 18507 1 15675 1 3174 56 33175 1 176.4 3 Latency 15533us 8142ms 2440ms 262ms 1289ms 780ms Version 1.96 ------Sequential Create------ --------Random Create-------- narvi-f21.doubledog -Create-- --Read--- -Delete-- -Create-- --Read--- -Delete-- files /sec %CP /sec %CP /sec %CP /sec %CP /sec %CP /sec %CP 16 13641 24 +++++ +++ 22702 17 18919 31 +++++ +++ +++++ +++ Latency 27724us 247us 292us 71us 30us 172us For comparison, here's what I see if I run the same test, same VM, same host but this time the file system is mounted from a device obtained using iscsi-initiator-utils within the VM, i.e., the 3rd bullet config above: bonnie++ -d . -r 2048 -u root:root <snip> Version 1.96 ------Sequential Output------ --Sequential Input- --Random- Concurrency 1 -Per Chr- --Block-- -Rewrite- -Per Chr- --Block-- --Seeks-- Machine Size K/sec %CP K/sec %CP K/sec %CP K/sec %CP K/sec %CP /sec %CP narvi-f21.double 4G 2051 89 103877 4 36286 3 4803 88 88166 4 163.6 3 Latency 7724us 191ms 396ms 48734us 73004us 1645ms Version 1.96 ------Sequential Create------ --------Random Create-------- narvi-f21.doubledog -Create-- --Read--- -Delete-- -Create-- --Read--- -Delete-- files /sec %CP /sec %CP /sec %CP /sec %CP /sec %CP /sec %CP 16 6531 18 +++++ +++ 16388 20 5924 15 +++++ +++ 17906 23 Latency 15623us 64us 92us 1281us 14us 256us My host is Fedora 20 running oVirt 3.5 (hosted-engine). VM is running Fedora Server 21. Tonight I tried updating the host with the Fedora virt preview repo and I didn't see any significant change in the performance. Where should I look next? _______________________________________________ Users mailing list Users(a)ovirt.org http://lists.ovirt.org/mailman/listinfo/users