Help. Recently I wrote that NAS and SAN access products couldn't share disk blocks. The reasoning was that a NAS stores blocks according to a file system and a SAN, not so constrained, doesn't. The blocks are organised differently on disk.

Well and good ... only not so good. Rory MacDonald of Technology Creative contacted me to say that Reldata's IP Storage Gateway 9200 can, in fact, do exactly that. He explained that the product organises the data blocks on disk at a layer below that at which a NAS or SAN would exist. As he said: "You create a LUN on top of that either for block or file storage."

This can be done on Fibre Channel disk or SATA disk; it really doesn't matter. The SAN or NAS Lun can co-exist on the disk or array with other LUNs and thus one virtual pool of storage exists from which either blocks or files can be served.

So the Reldata 9200 provides dedicated block-level iSCSI target volumes, or CIFS and NFS file systems, from a central virtualised storage volume pool.

Let's consider NetApp. A NetApp box could serve either file or block data because its Data ONTAP's system uses a Write Anywhere File Layout (WAFL), meaning that a CIFS or NFS access method is layered on top of WAFL.

Let's consider Windows Storage Server-based NAS filers: They can't serve blocks because the Windows file system dictates how the blocks are organised and accessed on disk.

What do you think? I've been given conflicting information about this, including info from the world's premier storage company. What's right? What do you think?


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