software iSCSI (debian wheezy) on Xen 6.2 + CS 4.3

[Erdősi Péter <fa...@niif.hu>]

Hi,

I faced with a strange problem, when configured iscsi storage one of my 
VM-s.
The Vm has 2 dedicated vif (which is connected to 10GB/s NICs), and i 
successfully logged in to iSCSI with them.
When I started some dd write test, it's going with 200-230MB/s (on whole 
100GB size, and the VM has 4G mem, so it was not cacheing)
After that, I started read test (simple copy from multipathed block 
device to /dev/null) and the read speed is around 30MB/s.

I know, it's not exactly a CS question, but may somebody faced this kind 
of problem too.

(cause the LUN is 48TB, I cannot add it to CS as primary storage, or if 
I do it, I need to add the whole 48T in ~2TB chunks... However if i 
connect iSCSI to Xen, the read and write speed is normal...)

Thanks,
  Peter

Re: software iSCSI (debian wheezy) on Xen 6.2 + CS 4.3

[Tim Mackey <tm...@gmail.com>]

Peter,

I'm going to recommend you to look at the various blog posts by Felipe
Franciosi on xenserver.org  (
http://xenserver.org/blog/blogger/listings/franciozzy.html).  He is one of
the performance engineers on the team, and has some pretty deep
understanding of why things behave the way they do.  There have also been a
number of storage performance threads on xs-devel at xenserver.org covering
results obtained with Creedence.  While some of the observations on't apply
to your situation, it will be a good starting point.

-tim

On Wed, Dec 3, 2014 at 7:02 PM, Erdősi Péter <fa...@niif.hu> wrote:

> Hi,
>
> I faced with a strange problem, when configured iscsi storage one of my
> VM-s.
> The Vm has 2 dedicated vif (which is connected to 10GB/s NICs), and i
> successfully logged in to iSCSI with them.
> When I started some dd write test, it's going with 200-230MB/s (on whole
> 100GB size, and the VM has 4G mem, so it was not cacheing)
> After that, I started read test (simple copy from multipathed block device
> to /dev/null) and the read speed is around 30MB/s.
>
> I know, it's not exactly a CS question, but may somebody faced this kind
> of problem too.
>
> (cause the LUN is 48TB, I cannot add it to CS as primary storage, or if I
> do it, I need to add the whole 48T in ~2TB chunks... However if i connect
> iSCSI to Xen, the read and write speed is normal...)
>
> Thanks,
>  Peter
>