24 Apr
2018
24 Apr
'18
1:44 a.m.
On 2018-04-24 01:30, Grant Taylor <gtaylor(a)tnetconsulting.net> wrote:
On 04/23/2018 04:15 PM, Warner Losh wrote:
That must have been somewhere in the middle of history in that case. Old
(proper) drives had/have track 0 at the outer edge. The disk loaded the
heads after spin up, and that was at the outer edge, and then you just
locked on to track 0, which should be near.
Heads had to be retracted for the disk pack to be replaced.
But this whole optimization for swap based on transfer speeds makes no
sense to me. The dominating factor in spinning rust is seek times, and
not transfer speed. If you place the swap at one end of the disk, it
won't matter much that transfers will be faster, as seek times will on
average be much longer, and that will eat up any transfer gain ten times
over before even thinking. (Unless all your disk ever does is swapping,
at which time the heads can stay around the swapping area all the time.)
Which is also why the file system for RSX (ODS-1) placed the index file
(equivalent of the inode table) at the middle of the disk by default.
Not sure if Unix did that optimization, but I would hope so. (Never dug
into that part of the code.)
Johnny
--
Johnny Billquist || "I'm on a bus
|| on a psychedelic trip
email: bqt(a)softjar.se || Reading murder books
pdp is alive! || tryin' to stay hip" - B. Idol
It's weird. These days lower LBAs perform
better on spinning drives.
We're seeing about 1.5x better performance on the first 30% of a drive
than on the last 30%, at least for read speeds for video streaming....
I think
manufacturers have switched things around on us. I'm used to
higher LBA numbers being on the outside of the disk. But I've seen
anecdotal indicators that the opposite is now true.