Andrew Holway wrote: > I've been playing around with GFS and Gluster a bit recently and this > has got me thinking... Given a fast enough, low enough latency network > might it but possible to have a Gluster like or GFS like memory space?
For random access, hard disk access times are milliseconds when the r/w head needs to move whereas Infiniband switch latency is less then ten microseconds. So if an algorithm needs highly random access over more memory than a single node, combining memory of a cluster might be the best solution for certain problems. I do not know of any parallel filesystem that uses memory mapping rather than parallel disks, but it seems like a useful utility. While it is possible to put a huge amount of memory into a single node, that node would be specialized, whereas using the memory of a cluster means that the same memory serves a general-purpose cluster when not being used for the specialized memory-based parallel file system. I once (many years ago) looked at PVFS, which has drivers for various interconnection hardware. It appeared to me that in order to modularize the software, read/write was done from the user program to virtual memory then copied over to DMA-able memory of the specific interconnect driver. It would be useful to write similar software with lower latency due to fewer copies. (I looked at PVFS because the source code is available.) No doubt some members of this list can provide much more up-to-date information and a more sophisticated description of the problem and possible solutions. I merely want to indicate that due to the low latency of some interconnects, for some applications it would be useful to combine distributed memory to look like a filesystem. I would suppose that for any given algorithm the highest performance could be obtained by distributing the calculation, whereas, my focus here is speeding-up applications that use conventional file I/O without rewriting the application but rather by changing the underlying file I/O implementation. Regards, Alan -- Alan Scheinine 200 Georgann Dr., Apt. E6 Vicksburg, MS 39180 Email: [email protected] Mobile phone: 225 288 4176 http://www.flickr.com/photos/ascheinine _______________________________________________ Beowulf mailing list, [email protected] sponsored by Penguin Computing To change your subscription (digest mode or unsubscribe) visit http://www.beowulf.org/mailman/listinfo/beowulf
