Anders Norrbring wrote:

Greg Freemyer skrev:

...

On 5/11/06, Anders Norrbring wrote:

...

Which transport method is generally faster than the other between two Linux boxes?

NFS or software based iSCSI?

Anders.

I don't know, but you do realize that the 2 are very different, right?

iSCSI exports a dedicated block device (ie. a disk drive, partition, etc.). Even the iSCSI server should not access the dedicated device except at the request of a client.

NFS exports a non-dedicated FS, so it has the potential to be more flexible and allows multiple clients as well as the server itself to access the same FS.

I think the eventual use case for iSCSI is to build a server with tons of reconfigurable disk space, then export pieces of that to a set of iSCSI clients. Very much like Fibre-Channel. Then if server 1 ends up needing less space and server 2 needs more you can shift your resources around.

I don't think the above reallocation capability works in generic linux yet. It would require LVM (or something like it) to be running on the server below the iSCSI driver.

Another use case for iSCSI that I believe does work today in Linux is to use iSCSI as the shared stored in a clustered FS like GFS. Be warned the GFS runs slower than local disk, so really have to need the cluster FS feature to justify the performance drop.

Greg

Thanks Greg, I know all that.. :) What I'm up to is to build a NAS with as high throughput as possible, and the differencies between the two ways aren't significant in this case, it should just be storage... It doesn't matter if it's a mounted directory (NFS) or a mounted device (iSCSI).

Anders.

This might be a good read: http://www.usenix.org/events/fast04/tech/radkov.html regards, Maarten -- ------------------------------------------------------- M.L.Hilgenga University of Groningen Department of Applied Physics Nijenborgh 4, 9747 AG Groningen The Netherlands tel: +31-50-3638045 fax: +31-50-3634886 email : m.l.hilgenga@rug.nl -------------------------------------------------------

Anders Norrbring wrote:

I know all that.. :) What I'm up to is to build a NAS with as high throughput as possible, and the differencies between the two ways aren't significant in this case, it should just be storage... It doesn't matter if it's a mounted directory (NFS) or a mounted device (iSCSI).

If you have a concrete application in mind, then your best bet is to benchmark it. Performance may vary a lot, in particular with different patterns of meta-data access. Try it out. You have a dedicated GBit-switch for that, don't you? Joachim -- =-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=- Joachim Schrod Email: jschrod@acm.org Roedermark, Germany