When doing random read IOPS to a ZFS-backed OST, the ZFS code will read the whole ZFS block from disk in order to do data checksum verification on the whole block. We may as well align the client read to the ZFS blocksize and fetch the whole ZFS block into client RAM so that the client could re-use those blocks if the file is small enough to fit into RAM. That avoids extra IO on the server that is not being used.