> I don't see much similarity between mirroring and raidz other than > that they both support redundancy.
A single parity device against a single data device is, in essence, mirroring. For all intents and purposes, raid and mirroring with this configuration are one and the same. > A RAID system with distributed parity (like raidz) does not have a > "parity device". Instead, all disks are treated as equal. Without > distributed parity you have a bottleneck and it becomes difficult to > scale the array to different stripe sizes. Agreed. Distributed parity is the way to go. Nonetheless, if I have an array with a single parity, then I still have one device dedicated to parity, even if the actual device which holds the parity information will vary from stripe to stripe. The point simply was that it might be straightforward to add a device and convert a raidz array into a raidz2 array, which effectively would be adding a parity device. An extension of that is to convert a raidz2 array back into a raidz array and increase its size without adding a device. -- This message posted from opensolaris.org _______________________________________________ zfs-discuss mailing list zfs-discuss@opensolaris.org http://mail.opensolaris.org/mailman/listinfo/zfs-discuss
