[Linux-cluster] using GNBD versus iSCSI

[Benjamin Marzinski]

On Tue, Mar 27, 2007 at 10:22:01PM +0200, David Shwatrz wrote:
>    Hello,
>    In short: what are the advantages/disadvantages when using GNBD versus
>    iSCSI for exporting storage in a cluster?

The only real advantage of using GNBD is that it has built in fencing. With
iSCSI, you still need some somthing to fence all the machines (unless your scsi
target supports SCSI-3 persistent resrvations). Theoretically, GNBD could
run faster, since it doesn't need to do the work to imitate a SCSI device, but
but there's a lot of work that needs to be done for GNBD to reach it's speed
potential. Since there isn't much active development of GNBD, if iSCSI
isn't already faster than it, it will eventually be. I am pretty much the only
GNBD developer, and aside from bug fixing, I do very little work on it. iSCSI
has an active community of developers. Using iSCSI also allows a much more
seemless transition to a hardware shared storage solution later on.

If you don't have any fencing hardware, and your iSCSI target doesn't support
SCSI-3 persistent reservations, then you should probably go with GNBD. Otherwise
it's up to you.

-Ben

>    Regards,
>    Dave S.

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