> From: Robert Milkowski [mailto:mi...@task.gda.pl] > > [In raidz] The issue is that each zfs filesystem block is basically > spread across > n-1 devices. > So every time you want to read back a single fs block you need to wait > for all n-1 devices to provide you with a part of it - and keep in mind > in zfs you can't get a partial block even if that's what you are asking > for as zfs has to check checksum of entire fs block.
Can anyone else confirm or deny the correctness of this statement? If you read a small file from a raidz volume, do you have to wait for every single disk to return a small chunk of the blocksize? I know this is true for large files which require more than one block, obviously, but even a small file gets spread out across multiple disks? This may be the way it's currently implemented, but it's not a mathematical requirement. It is possible, if desired, to implement raid parity and still allow small files to be written entirely on a single disk, without losing redundancy. Thus providing the redundancy, the large file performance, (both of which are already present in raidz), and also optimizing small file random operations, which may not already be optimized in raidz. _______________________________________________ zfs-discuss mailing list zfs-discuss@opensolaris.org http://mail.opensolaris.org/mailman/listinfo/zfs-discuss
