[ovirt-users] Poor iSCSI Performance

[InterNetX - Juergen Gotteswinter]

Hi,

already captured some iscsi Traffic of both Situations and compared them?

MTU maybe?


Juergen

Am 18.02.2015 um 02:08 schrieb John Florian:
> 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?
> 
> 
> 
> 
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