[422] in Release_7.7_team
Sun Swap partition performance.
daemon@ATHENA.MIT.EDU (Bill Cattey)
Fri Jan 19 21:08:12 1996
Date: Fri, 19 Jan 1996 21:08:04 -0500 (EST)
From: Bill Cattey <wdc@MIT.EDU>
To: trb@MIT.EDU, release-team@MIT.EDU
Using our Alliance Plus contact with Sun I posed the question:
With the new Solaris 2.4 might there be performance improvements if the
/usr partition was moved closer to the center of the disk.
IE change:
root/swap/usr
to
root/usr/swap
Jim Hill answered the question:
Maybe.
Issues of interest:
As we expected, the layout of the filesystems will effect the performance due
to the size of the average seek time between the sections on the disk.
Also it was confirmed that Solaris 2.4 does swap read-only text pages
directly from the files so a performance improvement could occur in
cases of very text-intensive job mixes.
Unexpectedly, it was mentioned that many disk drive makers do variable
sectoring, placing more sectors on the OUTER cylinders than inner ones
before providing the logical blocks to the SCSI interface. This has the
effect of making OUTER cylinders sometimes higher performance than inner
ones. Unfortunately, the only way to know for sure if such an
enhancement has occurred is to find out who made the disk, and inquire
of their senior technical folks.
Apparently Sun Storage Arrays and many of the 3 1/2 inch drives they
ship with their machines have this enhancement.
I glean this useful information:
1. Gauging performance of swap placement on the drives is even more
complicated than we expected, and we already KNEW it was complicated.
2. Exchanging swap and usr should not have much of a negative impact
because the performance of the drive and the operating system has been
enhanced to smooth out the differences.
3. There is a book out that I plan to get for us: _Performance_Tuning_
by Adrian Cokrov (spelling unclear), which has been recommended as
covering this and many other issues in good detail.
-wdc
