Greetings:
As usual, the replies were prompt and most helpful.
The original question was:
1) Is there a performance sacrifice with having swap space on 2 (or more)
disks?
Answer: Quite the contrary, there is actually a performance increase
due to the fact that IO to the disks can occur simultaneously, thus
decreasing access/write times.
2) Can disks have less than 3 partitions (ie one for swap and one for the
rest of the disk).
Answer: From the many replies I received, the consensus was that this
was possible - indeed many had done just that ("b" partition for swap,
"a" or "g" for everything else) However, there were differing opinions as to
what is the best thing to do. Since the disk label is at the begining
of the disk, putting swap at the beginning of the disk is a no-no. Some
recommended "optimal" placement of the swap partition to enhance
performance.
Selden E Ball Jr <SEB_at_LNS62.LNS.CORNELL.EDU> sez:
It is true that Digital UNIX requires that "a" start at block 0. However,
there is no problem making partition "a" large enough for your data and
putting "b" (for swapping) at the outside edge of the disk, That region
actually yields better performance, since modern disks have more sectors per
cylinder at larger radii, and thus a higher data bitrate.
The Good Dr. Thomas P. Blinn <tpb_at_zk3.dec.com> sez:
I have just an "a" and "b" partition in use on some of my disks. You can do
the allocation just about any way you like. In fact, with an RZ28, you may
want to put files at the beginning of the disk, swap in the middle, and
other inactive but sometimes needed files in a third partition on the other
side of the swap partition. This works. What you want to avoid is putting
swap partitions on a heavily accessed disk, if you can avoid it.
Many Many thanks to all who replied:
Per Boussard <pb_at_physto.se>
Jay Maynard <jmaynard_at_admin5.hsc.uth.tmc.edu>
Hellebo Knut <bgk1142_at_bggfu2.nho.hydro.com>
John Stoffel <john_at_WPI.EDU>
Selden E Ball Jr <SEB_at_LNS62.LNS.CORNELL.EDU>
Drew Kramer <drew_at_ny.ox.com>
David Warren <warren_at_atmos.washington.edu>
Per Boussard <pb_at_physto.se>
Reto Haeni <haeni_r_at_vptt.ch>
lboyd_at_isd.csc.com (Larry Boyd (CSC))
Steve Godersky <steveg_at_iii.com>
fabrice_at_cisk.atmos.Ucla.EDU (Fabrice Cuq)
Anthony D'Atri <aad_at_statsci.com>
luchini_at_siberia.ups-tlse.fr (Marco Luchini)
"Dr. Tom Blinn, 603-881-0646" <tpb_at_zk3.dec.com>
If you'd like a copy of all replies, send me a request and I'll make
them available to all interested parties.
Thanks once again!
_____________________________________________________________________
Cary A. Talbot, Hydraulic Engineer US Army Corps of Engineers
ATTN: CEWES-HH-G Waterways Experiment Station
3909 Halls Ferry Road
Vicksburg, Mississippi 39180
phone:(601)634-4286 fax:(601)634-4208 email:talbot_at_hl.wes.army.mil
Received on Mon May 22 1995 - 14:47:24 NZST