I am looking for a little help to find out what block sizes (as shown by stat) by Linux based parallel filesystems.
You can find this by running stat on a file. For example on Lustre: # stat /lfs0/bigfile File: `/lfs0//bigfile' Size: 1073741824 Blocks: 2097160 IO Block: 2097152 regular file Device: 59924a4a8h/1502839976d Inode: 45361266 Links: 1 Access: (0644/-rw-r--r--) Uid: ( 0/ root) Gid: ( 0/ root) Access: 2010-06-17 20:24:32.000000000 +0000 Modify: 2010-06-17 20:16:49.000000000 +0000 Change: 2010-06-17 20:16:49.000000000 +0000 If anyone can run this test and provide me with the filesystem and result (as well as the OS used), it would be a big help. I am specifically looking for GPFS results, but other products (Panasas, GlusterFS, NetApp GX) would be helpful. Why do I care? Because in netcdf, when nf_open or nf_create are called, it will use the blocksize that is found in the stat structure. On lustre it is 2M so writes are very fast. However, if the number comes back as 4k (which some filesystems do), then writes are slower than they need to be. This isn't just a netcdf issue. The Linux tool cp does the same thing, it will use a block size that matches the specified blocksize of the destination filesystem. Thanks, Craig _______________________________________________ Beowulf mailing list, Beowulf@beowulf.org sponsored by Penguin Computing To change your subscription (digest mode or unsubscribe) visit http://www.beowulf.org/mailman/listinfo/beowulf
