... > For modern disks, media bandwidths are now getting to > be > 100 MBytes/s. > If you need 500 MBytes/s of sequential read, you'll > never get it from > one disk.
And no one here even came remotely close to suggesting that you should try to. > You can get it from multiple disks, so the questions > are: > 1. How to avoid other bottlenecks, such as a > shared fibre channel > ath? Diversity. > 2. How to predict the data layout such that you > can guarantee a wide > spread? You've missed at least one more significant question: 3. How to lay out the data such that this 500 MB/s drain doesn't cripple *other* concurrent activity going on in the system (that's what increasing the amount laid down on each drive to around 1 MB accomplishes - otherwise, you can easily wind up using all the system's disk resources to satisfy that one application, or even fall short if you have fewer than 50 disks available, since if you spread the data out relatively randomly in 128 KB chunks on a system with disks reasonably well-filled with data you'll only be obtaining around 10 MB/s from each disk, whereas with 1 MB chunks similarly spread about each disk can contribute more like 35 MB/s and you'll need only 14 - 15 disks to meet your requirement). Use smaller ZFS block sizes and/or RAID-Z and things get rapidly worse. - bill This message posted from opensolaris.org _______________________________________________ zfs-discuss mailing list zfs-discuss@opensolaris.org http://mail.opensolaris.org/mailman/listinfo/zfs-discuss
