> >We have designed a new stackable file system that we called RAIF: > >Redundant Array of Independent Filesystems. > > > >Similar to Unionfs, RAIF is a fan-out file system and can be mounted over > >many different disk-based, memory, network, and distributed file systems. > >RAIF can use the stable and maintained code of the other file systems and > >thus stay simple itself. Similar to standard RAID, RAIF can replicate the > >data or store it with parity on any subset of the lower file systems. RAIF > >has three main advantages over traditional driver-level RAID systems: > > > >1. RAIF can be mounted over any set of file systems. This allows users to > > create many more useful configurations. For example, it is possible to > > replicate the data on the local and remote disks, and stripe the data on > > the local hard drives and keep the parity (or even ECC to tolerate > > multiple failures) on the remote server(s). In the latter case, all the > > read requests will be satisfied from the fast local disks and no local > > disk space will be spent on parity. > > As for striping on a simplistic level, look at the Equal File > Distribution patch for unionfs :-) > > http://www.mail-archive.com/unionfs@xxxxxxxxxxxxxxxxxxxxxx/msg01936.html > > Files are stored normally so that after the union is unmounted, the > files appear in one piece (unlike real RAID0 over two block devices). RAIF supports rules that describe how to store particular files or groups of files. A rule with RAIF level 0 (which is similar to RAID level 0) and a special striping unit size = '-1' will do the same (distribute the files on the lower file systems) for files that match any given file name pattern. A rule with level 4 and striping unit size = '-1' will distribute files on several file systems and store an extra copy of the files on a dedicated file system (e.g., an NFS mount with lots of space). Now guess what RAIF's level 6 will do with a special striping unit size = '-1' :-) Nikolai. ---------------- Nikolai Joukov, Ph.D. Filesystems and Storage Laboratory Stony Brook University - To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
