Re: [Xen-users] Xen - AoE benchmarks

[Markus Hochholdinger <Markus@xxxxxxxxxxxxxxxxx>]

Hi,

Am Donnerstag, 14. August 2008 04:09 schrieb Fajar A. Nugraha:
> Markus Hochholdinger wrote:
> > The only reason i'm looking forward to use aoe is because the
> > disconnection of malfunctioning storage servers is better handled than
> > with gnbd. gnbd (in "No Cluster" mode) waits forever if the server dies
> > and i had to write my own programs to handle such a situation. aoe just
> > gives i/o error, and that's what i want.
> Is there a reason whay you're not looking at iscsi?
> Redhat's iscsi-initiator-utils (from open-iscsi) has
> node.session.timeo.replacement_timeout, which
> "specify the length of time to wait for session re-establishment before
> failing SCSI commands back to the application when running the Linux
> SCSI Layer error handler". I assume this is what you want.

yeah, i'm very satisfied with iscsi. It seems _there_ was the development the 
last years. My first tests indicate that it has a similar load on the server 
side as gnbd has. The load on the client was not really noticeable. And the 
performance is at least equal to gnbd. Read throughput is slightly better and 
write throughput is more than 5% better than with gnbd. I'm impressed. I'll 
make more tests with iscsi against gnbd and it seems iscsi will be the choice 
for the future.

I used http://iscsitarget.sourceforge.net/ for the server and 
http://www.open-iscsi.org/ for the client. Interesting is that the server 
part is a kernel module and not user land software like with gnbd and aoe 
(vblade).

I tried the disconnecting feature and it is really what i want. I just turned 
off the iscsi target and waited till my raid1 degraded. Then turned on the 
iscsi target and simply resynced my raid1. I didn't had to do any 
re-discovering or resetting anything! That's what i want.

The only disadvantage i see so far is the complexity of iscsi. But this 
shouldn't be a excuse.


-- 
greetings

eMHa

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