--On 1 November 2010 15:45:12 -0600 Andreas Dilger <adilger.kernel@xxxxxxxxx> wrote:
What is it you really want to do in the end? Shared concurrent writers to the same file? High-bandwidth IO to the underlying disk?
High bandwidth I/O to the underlying disk is part of it - only one reader/writer per file. We're really using ext4 just for its extents capability, i.e. allocating space, plus the convenience of directory lookup to find the set of extents. It's easier to do this than to write this bit from scratch, and the files are pretty static in size (i.e. they only grow, and grow infrequently by large amounts). The files on ext4 correspond to large chunks of disks we are combining together using an device-mapper type thing (but different), and on top of that lives arbitary real filing systems. Because our device-mapper type thing already understands what blocks have been written to, we already have a layer that prevents the data on the disk before the file's creation being exposed. That's why I don't need ext4 to zero them out. I suppose in that sense it is like the swap file case. Oh, and because these files are allocated infrequently, I am not /that/ concerned about performance (famous last words). The performance critical stuff is done via direct writes to the SAN and don't even pass through ext4 (or indeed through any single host). -- Alex Bligh _______________________________________________ Ext3-users mailing list Ext3-users@xxxxxxxxxx https://www.redhat.com/mailman/listinfo/ext3-users
