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Hi all,<br>
<br>
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:<br>
<ul>
<li>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<br>
</li>
<li>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<br>
</li>
<li>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</li>
</ul>
<p>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.<br>
</p>
<p>Here's a typical example of the poor performance I get (as tested
with bonnie++) with the normal virtual disk setup:<br>
</p>
<p><tt># bonnie++ -d . -r 2048 -u root:root<br>
<snip><br>
Version 1.96 ------Sequential Output------ --Sequential
Input- --Random-</tt><tt><br>
</tt><tt>Concurrency 1 -Per Chr- --Block-- -Rewrite- -Per
Chr- --Block-- --Seeks--</tt><tt><br>
</tt><tt>Machine Size K/sec %CP K/sec %CP K/sec %CP K/sec
%CP K/sec %CP /sec %CP</tt><tt><br>
</tt><tt>narvi-f21.double 4G 806 91 18507 1 15675 1 3174
56 33175 1 176.4 3</tt><tt><br>
</tt><tt>Latency 15533us 8142ms 2440ms
262ms 1289ms 780ms</tt><tt><br>
</tt><tt>Version 1.96 ------Sequential Create------
--------Random Create--------</tt><tt><br>
</tt><tt>narvi-f21.doubledog -Create-- --Read--- -Delete--
-Create-- --Read--- -Delete--</tt><tt><br>
</tt><tt> files /sec %CP /sec %CP /sec %CP /sec
%CP /sec %CP /sec %CP</tt><tt><br>
</tt><tt> 16 13641 24 +++++ +++ 22702 17 18919
31 +++++ +++ +++++ +++</tt><tt><br>
</tt><tt>Latency 27724us 247us 292us
71us 30us 172us</tt><br>
<br>
</p>
<p>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:<br>
</p>
<p><tt>bonnie++ -d . -r 2048 -u root:root</tt><tt><br>
</tt><tt><snip></tt><tt><br>
</tt><tt>Version 1.96 ------Sequential Output------
--Sequential Input- --Random-</tt><tt><br>
</tt><tt>Concurrency 1 -Per Chr- --Block-- -Rewrite- -Per
Chr- --Block-- --Seeks--</tt><tt><br>
</tt><tt>Machine Size K/sec %CP K/sec %CP K/sec %CP K/sec
%CP K/sec %CP /sec %CP</tt><tt><br>
</tt><tt>narvi-f21.double 4G 2051 89 103877 4 36286 3 4803
88 88166 4 163.6 3</tt><tt><br>
</tt><tt>Latency 7724us 191ms 396ms
48734us 73004us 1645ms</tt><tt><br>
</tt><tt>Version 1.96 ------Sequential Create------
--------Random Create--------</tt><tt><br>
</tt><tt>narvi-f21.doubledog -Create-- --Read--- -Delete--
-Create-- --Read--- -Delete--</tt><tt><br>
</tt><tt> files /sec %CP /sec %CP /sec %CP /sec
%CP /sec %CP /sec %CP</tt><tt><br>
</tt><tt> 16 6531 18 +++++ +++ 16388 20 5924
15 +++++ +++ 17906 23</tt><tt><br>
</tt><tt>Latency 15623us 64us 92us
1281us 14us 256us</tt><br>
</p>
<p>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?<br>
</p>
<p><br>
</p>
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