jawitz@ursa.UUCP (Eric Jawitz) (06/04/90)
<dlg6627@uxa.cso.uiuc.edu> writes - >Don't forget to ask for 1:1 interleave for the controller card !. >I had some experience to purchase computer(s) from CompuAdd, they >usually give us 3:1 or 2:1 if we didn't ask. I'm curious to know what a 1:1 interleave disk controller card does for performance. I have two 40 meg. Seagate (ST 251-1) drives in my 386/25 system on which I recently ran SpinRite which supposedly optimizes the disk interleaving. SpinRite reported that the interleaving was set at 3:1 (yielding about a 176K/sec. throughput) and that the optimum interleave would be 2:1 (resulting in a 50% greater throughput). So I let SpinRite do its stuff and change the interleaving. The Norton SI disk index shows no change in performance between 3:1 and 2:1 disk interleaving (both yield an index of 2.6). I assume this is because SI does not measure throughput to derive the index. On the other hand, the Checkit disk benchmark shows a throughput of about 250K/sec. with 2:1 compared with 176K/sec. with 1:1. It seems, therefore, that SpinRite did make a difference. The talk about a 1:1 interleave disk controller puzzles me because if the interleave can be changed with software, what's the need for a special controller card? How is a 1:1 controller any different from my (apparently) 3:1 controller? Should I consider getting one? On a related note, my system has a selectable bus speed (8/12 megahertz I believe). I realize that some cards may not work at the higher speed. However assuming that everything checks out OK, are there any drawbacks to increasing the speed? Would the system run hotter? Would I be shortening the life of my boards? Am I likely to see an increase in disk throughput? Is this in turn likely to affect the optimum interleaving for my system? If you have insights into any or all of the above questions, I'd be most grateful to hear from you. -Ed Thieberger beareq!thieb@wheaties.ai.mit.edu
tmurphy@wpi.wpi.edu (Tom [Chris] Murphy) (06/05/90)
Interleave refers to the spacing between consecutive sectors on a hard drive.
1:1 is the closest sectors can be placed, as this is a sequential layout.
Not all controllers can deal with this rate, and my have to let the disk spin
around once before getting the next sector. A 1:1 controller can handle
this rate properly, giving the fastest possible access on the drive. But
other controllers may work OPTIMALLY at interleaves of 1:2 or 1:3. Depends
on your hardware. Spinrite reports the optimal interleve for a system.
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Worcester Polytechnic Institute CAD Lab | tmurphy@zaphod.wpi.edu
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Guns don't kill people, people kill people ... usually with guns.silver@xrtll.uucp (Hi Ho Silver) (06/05/90)
In article <4627@ursa.UUCP> jawitz@ursa.UUCP (Eric Jawitz) writes:
$I'm curious to know what a 1:1 interleave disk controller card does for
$performance. [...]
$The talk about a 1:1 interleave disk controller puzzles me because if
$the interleave can be changed with software, what's the need for a
$special controller card? How is a 1:1 controller any different from
$my (apparently) 3:1 controller? Should I consider getting one?
I guess a brief, nontechnical overview of interleave is in order. In
the past, the typical disk drive could provide information to the controller
faster than the controller could ship it off to the PC, so by the time
the controller was ready to receive the next sector from the disk drive,
the read/write head had already gone past the next sector and you'd have
to wait until the disk completed a revolution, which obviously is not good
for performance. To remedy this, interleave factors are used so that the
position the read/write head is in once the controller is ready for the
next sector is about where the next sector in the file will be on the
diskette. I hope that explains it well enough ... this is something that's
much easier to explain with a diagram.
So how is the 1:1 controller different? Well, it can handle the
data quickly enough that interleave factors are not needed, and it allows
you to use the disk drive to the limit of its performance.
$On a related note, my system has a selectable bus speed (8/12 megahertz I
$believe). I realize that some cards may not work at the higher speed. However
$assuming that everything checks out OK, are there any drawbacks to increasing
$the speed? Would the system run hotter? Would I be shortening the life
$of my boards? Am I likely to see an increase in disk throughput? Is this
$in turn likely to affect the optimum interleaving for my system?
Just because everything checks out OK when you try it out for a minute
or two doesn't mean it will always work OK ... if you find it works at the
higher rate, don't be surprised if you start thinking there are gremlins
in your computer from time to time, as some cards may be at the very limit
of their performance and may work some of the time but not all of the time
at the higher rate.
If all your cards can handle it, though, you should have no problems.
The life of your system may be shortened a little bit, but most systems
will normally last beyond the time when you want to replace them with
more recent technology anyway. Also, as long as you make sure everything
doesn't get clogged up with dust, you should have enough airflow in most
machines to keep things adequately cool. As for disk throughput, you
will quite likely have to alter the interleave for optimal performance
if you change the bus speed, since that alters the rate at which the
controller can transfer data between itself and the PC.
--
/Nikebo \ Nikebo says "Nikebo knows how to post. Just do it."\silver@xrtll/
/---------\_____________________________________________________\----------/
/yunexus!xrtll!silver (L, not 1)\ Hi Ho Silver \ just silver for short /
/Silver: Ever Searching for SNTF \ Life sucks. \ someone buy me a BEER! /jca@pnet01.cts.com (John C. Archambeau) (06/05/90)
jawitz@ursa.UUCP (Eric Jawitz) writes: ><dlg6627@uxa.cso.uiuc.edu> writes - > >>Don't forget to ask for 1:1 interleave for the controller card !. >>I had some experience to purchase computer(s) from CompuAdd, they >>usually give us 3:1 or 2:1 if we didn't ask. > >I'm curious to know what a 1:1 interleave disk controller card does for >performance. I have two 40 meg. Seagate (ST 251-1) drives in my 386/25 >system on which I recently ran SpinRite which supposedly optimizes >the disk interleaving. SpinRite reported that the interleaving was set >at 3:1 (yielding about a 176K/sec. throughput) and that the optimum >interleave would be 2:1 (resulting in a 50% greater throughput). So I >let SpinRite do its stuff and change the interleaving. The Norton SI >disk index shows no change in performance between 3:1 and 2:1 disk >interleaving (both yield an index of 2.6). I assume this is because >SI does not measure throughput to derive the index. On the other hand, >the Checkit disk benchmark shows a throughput of about 250K/sec. with 2:1 >compared with 176K/sec. with 1:1. It seems, therefore, that SpinRite did >make a difference. > >The talk about a 1:1 interleave disk controller puzzles me because if >the interleave can be changed with software, what's the need for a >special controller card? How is a 1:1 controller any different from >my (apparently) 3:1 controller? Should I consider getting one? > >On a related note, my system has a selectable bus speed (8/12 megahertz I >believe). I realize that some cards may not work at the higher speed. However >assuming that everything checks out OK, are there any drawbacks to increasing >the speed? Would the system run hotter? Would I be shortening the life >of my boards? Am I likely to see an increase in disk throughput? Is this >in turn likely to affect the optimum interleaving for my system? > >If you have insights into any or all of the above questions, I'd be most >grateful to hear from you. Your 1:1 interleave controllers have the ability to buffer an entire track on the card. I interleave the drive at what the controller is rated at. My current controller is a 2:1 WA3-16 (WD1003-WA2 clone) and the optimal interleave via inspection was what the manufacturer rated the controller at which is 2:1. If you jump to a WD1006V controller and interleave the drive at 1:1, I'd be surprised if you didn't get a performance increase. Yes, it is true you can change the interleave via software, the issue of optimal interleave though is if your hardware configuration can handle 1:1 or not and yield optimal performance. So, thus, the interleave of the controller is the optimal interleave the controller is rated at by the manufacturer of the controller. As for bus speed, it may or may not. I doubt it would since it's your controller that's reading the drive, it's only shooting the data across the bus. A word of warning, if you deviate from the de facto ISA bus speed standard of 8 MHz, you can damage cards that are pushed at a higher speed. I killed an internal modem that couldn't handle the increase in bus speed when I pulled it out of my XT and put it into my 286 a couple of years back. I neglected to configure the bus speed at 8 MHz. My drive controller worked just fine since it's rated to run up to 16 MHz. So a word to the wise, unless you buy high speed cards, stay at the de facto standard of 8 MHz on the ISA bus. // JCA /* **--------------------------------------------------------------------------* ** Flames : /dev/null | Small memory model only for ** ARPANET : crash!pnet01!jca@nosc.mil | Unix? Get the (*bleep*) out ** INTERNET: jca@pnet01.cts.com | of here! ** UUCP : {nosc ucsd hplabs!hd-sdd}!crash!pnet01!jca **--------------------------------------------------------------------------* */