[Linux-cluster] SAN, software raid, iscsi or GNBD, GFS

Markus Hochholdinger Markus at hochholdinger.net
Tue Aug 12 18:04:46 UTC 2008


Am Donnerstag, 7. August 2008 14:28 schrieb Alex:
> I would like to build a SAN using cheap hardware.
> Let say that we have N computers (N>8) exporting their volumes (volX, where
> X=N) using ataoe or iscsi or gnbd protocol. Each volX is arround 120GB.

i'm in a similar situation. I've a setup with gnbd (with "No Cluster" 
configuration) and i'm trying to switch to aoe, because i read that aoe 
should perform better.

Well, my tests indicate a very poor performance for aoe! I setup gnbd without 
great hassle and tweaking. Performance is as fast as the network and the 
disks can handle.

First, with aoe i had very poor performance. I had to use latest aoe module, 
latest vblade and a lot of network tweaking (jumbo frames, ..) to have nearly 
the performance from gnbd. OK, with reads i'm a litter faster with aoe.
But the drawback is that vblade needs a lot more cpu than gnbd_serv! So if you 
export more than one block device with aoe your performance will drop.

> Cons:
> - Using iSCSI also allows a much more seemless transition to a hardware
> shared storage solution later on
> - GNBD seems to be slower then ISCSI and lot of work that needs to be done
> for GNBD to reach its full speed potential.

Have you tested this? As far as i can tell (my tests are over two years old) 
iscsi needed much more cpu and had less performance than gnbd.


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