There is a particular kind of application, single-client and serial process, for which a striped file system using RAM disk would be very useful. Consider reading small blocks at random locations on a hard disk. The latency of the HDD could be large, a few milliseconds. Adding more HDD's does not solve the problem, unlike an application based on streaming. Adding more disks and parallelizing the program could be a solution but sometimes there is no time to parallelize the program.
A possible solution is RAM disk. But if we put, for example, 64 GB of RAM on a single computer then that computer becomes specialized and expensive, whereas the need for a huge amount of RAM may be only temporary. An alternative is to use a cluster of nodes, a typical Beowulf cluster. For example, using a striped file system over 16 nodes where each node has 4 GB of RAM. Each node would have a normal amount of RAM and yet could provide the aggregate storage of 64 GB when the need arises. While we have not yet created this configuration, I suppose that Gbit Ethernet could provide 100 microsecond latency and Infiniband or Myrinet could provide 10 microsecond latency. Much, much less than the seek time of a HDD. The idea is so simple that I imagine it has already been done. I would be interested in learning from other sites that have used this method with the Lustre file system. best regards, _______________________________________________ Lustre-discuss mailing list [email protected] https://mail.clusterfs.com/mailman/listinfo/lustre-discuss
