>With ZFS however the in-between cache is obsolete, as individual disk caches >can be used >directly. I also openly question whether even the dedicated RAID >HW is faster than the newest >CPUs in modern servers.
Individual disk caches are typically in the 8-16 MB range; for 15 disks, that gives you about 256 MB. A RAID with 15 drives behind it might have 2-4 GB of cache. That's a big improvement. The dedicated RAID hardware may not be faster than the newest CPUs, but as a friend of mine has pointed out, even though delegating a job to somebody else often means it's done more slowly, it frees him up to do his other work. (It's also pondering the difference between latency and bandwidth. When parity is computed inline with the data path, as is often the case for hardware controllers, the bandwidth is relatively low since it's happening at the speed of data transfer to an individual disk, but the latency is effectively zero, since it's not adding any time to the transfer.) This message posted from opensolaris.org _______________________________________________ zfs-discuss mailing list zfs-discuss@opensolaris.org http://mail.opensolaris.org/mailman/listinfo/zfs-discuss
