At IEEE Cluster 2009 last week Dell was talking up the arguments in favor of iSCSI for storage clusters in HPC
The first approach — called an indirect SAN — has servers re-exporting iSCSI storage via a traditional parallel file system. With the second approach — called a direct SAN — the compute nodes attach directly to a clustered file system on the iSCSI storage via software iSCSI initiators.
…The scalability of the direct approach is limited by the capabilities of the underlying storage. For example, the MD3000i is limited to 16 client nodes while the PS 6000 series iSCSI SAN can scale to hundreds of client nodes. The advantage of the direct appraoch is that it eliminates the cost and performance associated with the data movers. The direct approach allows customers to allocate more of their budget to the workhorses that solve the problems.
Of course this is not ground breaking scientific research, but the direct SAN approach is a novel idea that merits further exploration. Given that commodity, standards based hardware and open source software are the forces that drive the widespread adoption of HPC clusters, iSCSI seems like a natural fit. iSCSI can provide flexible, block level access to shared storage without eroding a cluster’s favorable economics.
More, with pictures and links, at the link above.