IBM multi-petabyte cloud defies XIV storage
How does it scale that much?
Indirectly scaling out XIV
The XIV is a block storage device whereas GPFS is, obviously, a file system. Could we be looking at BladeCenter servers running GPFS and acting as network-attached storage (NAS) heads, each with its own XIV array? Scaling the system would mean adding more BladeCenter/GPFS servers plus an XIV array with all the inter-nodal functionality carried out at the server level. IBM says (pdf): "In addition to nodes that are directly attached to the storage, a single GPFS file system can be accessed by thousands of nodes using a LAN connection like Ethernet or InfiniBand."
That sounds promising. It has this to say about GPFS and block I/O: "GPFS has a very flexible cluster architecture providing many options to develop a solution including: direct attached, network block I/O, a combination of the two and multi-site operations... the network block I/O (also called network shared disk or NSD)... is a software layer that forwards block I/O requests from an NSD client application node to the LAN, which then passes the request to an NSD storage node to perform the disk I/O and pass data back to the client. GPFS makes the LAN-based I/O operation transparent to the application. Using a Network Block I/O configuration can be more cost-effective than a full-access SAN and can be used to tie together systems across a WAN."
XIV is an NSD storage node in this scenario.
Which XIV scaling route is IBM going to use: scaling up XIV nodes; scaling out XIV nodes; or indirect scaling out with nodes composed of BladeCenter/GPFS servers each with its own XIV array?
From here it looks as if existing XIV arrays linked to BladeCenter server/GPFS nodes will be tied together in a scale-out architecture with the GPFS/BladeCenter servers performing the interconnect functions. That seems far more likely, and easier to accomplish than scaling XIV up internally or developing XIV super clusters. ®
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