On Apr 02, 2007 05:57 -0700, i.vlad@xxxxxxxxx wrote: > My question is -- can the filesystem actually read/write to files truly > in parallel (more processors -- faster read/write), or if I write such > a code the I/O commands from the CPUs will just queue after each other > and it would be the same thing as using a single CPU? If parallel I/O > is possible, can it be accomplished entirely transparently, or using > special libraries, or only in special circumstances, like reading in > parallel with N CPUs from N different physical disks? Or only on some > types of hardware? Is there a max nr of threads/processes that can > write to disk in parallel? If ext3 does not do this, which (stable) > Linux filesystem does it? You can do this with Lustre (www.lustre.org), which is a GPL parallel, distributed filesystem that runs on top of ext3 (essentially ext4 though). Since Lustre does its own distributed extent locking on a file, it is possible to do fully parallel IO to a single file from multiple nodes. > I know that the vast majority of clusters use something else than ext3 > (NFS, Lustre, etc), but the question still stands because: (1) individual > nodes in commodity clusters do have very often individual ext3 disks that > are used for temporary files (intermediate computational results); (2) > grid computers made of standalone user machines are likely to have the > most common filesystem, ext3; (3) There are scientific data processing > steps that need to be done on a single shared-memory machine because of > intensive data exchange between CPUs. (4) Software development is easier > to do on a single machine (i.e. powerful multi-core laptop). We are looking to make even single-node file locking better than just i_mutex (i.e. fine-grained extent locking in the VFS) but this is not a high priority task for us, since we target large systems mostly. If anyone is interested in doing such work we would definitely want to help out with it. Cheers, Andreas -- Andreas Dilger Principal Software Engineer Cluster File Systems, Inc. _______________________________________________ Ext3-users mailing list Ext3-users@xxxxxxxxxx https://www.redhat.com/mailman/listinfo/ext3-users
