On Wed, Feb 2 at 20:45, Edward Ned Harvey wrote:
For sustained throughput, I don't measure in IOPS. I measure in MB/s, or Mbit/s. For a slow hard drive, 500Mbit/s. For a fast one, 1 Gbit/s or higher. I was surprised by the specs of the seagate disks I just emailed a moment ago. 1Gbit out of a 7.2krpm drive... That's what I normally expect out of a 15krpm drive.
It used to be that enterprise grade, higher RPM devices used more expensive electronics, but that's not really the case anymore. It seems most vendors are trying to use common electronics across their product lines, which generally makes great business sense. These days I think most HDD companies get their channel working at a certain max bitrate, and format their drive zones to match that bitrate at the max radius where velocity is the highest. This is a bit of a simplification, but it's the general idea. When the drive is spinning the media less quickly, in a 7200 RPM device, they can pack the bits in more tightly, which lowers overall cost because they need fewer heads and platters to achieve a target capacity. It just so happens that the max bits/second flying under the read head is a constant pegged to the channel design. All other things being equal, the 15k and the 7200 drive, which share electronics, will have the same max transfer rate at the OD.
I know people sometimes (often) use IOPS even when talking about sequential operations, but I only say IOPS for random operations.
Me too, though not everyone realizes how much overhead there can be in small operations, even sequential ones. --eric -- Eric D. Mudama edmud...@bounceswoosh.org _______________________________________________ zfs-discuss mailing list zfs-discuss@opensolaris.org http://mail.opensolaris.org/mailman/listinfo/zfs-discuss
