> If you've got the internal system bandwidth to drive all drives then RAID-Z > is definitely > superior to HW RAID-5. Same with mirroring.
You'll need twice as much I/O bandwidth as with a hardware controller, plus the redundancy, since the reconstruction is done by the host. For instance, to be equivalent to the performance of a mirrored array on a single 4 Gb FC channel, you need to use four 4 Gb FC channels, at least if you can't tolerate a 50% degradation during reconstruction; or two 4 Gb FC channels if you don't mind the performance loss during reconstruction. RAID-Z also uses system CPU and memory bandwidth, which is fine for file servers since they're normally overprovisioned there anyway, but may be less appropriate for some other uses. > HW RAID can offload some I/O bandwidth from the system, but new systems, > like Thumper, should have more than enough bandwidth, so why bother with > HW RAID? Thumper seems to be designed as a file server (but curiously, not for high availability). It's got plenty of I/O bandwidth. Mid-range and high-end servers, though, are starved of I/O bandwidth relative to their CPU & memory. This is particularly true for Sun's hardware. Anton This message posted from opensolaris.org _______________________________________________ zfs-discuss mailing list zfs-discuss@opensolaris.org http://mail.opensolaris.org/mailman/listinfo/zfs-discuss
