RE: Squid on IDE

From: William Stucke <>
Date: Mon, 26 Oct 1998 11:20:02 +0200

On Monday, October 26, 1998 9:28 AM, Marc van Selm
[] wrote:
> At 12:03 PM 10/23/98 -0400, Mike.Richards wrote:
> >Gustavo,
> > DO NOT USE IDE for heavy disk IO application servers, e.g. Sun Ultra
> > 10,
> > it will/does not perform anywhere near SCSI.....

Usually, but not always true - beware of the SCSI manufacturers' propaganda
;-) For a single disk, the raw speeds are as follows : (Data from various
sources, some slightly contradictory!)

ESDI: 3 MB/s - very old stuff!
IDE (= ATA): 4 - 12 MB/s - 1981 to ~1990
EIDE (ATA Mode 2): 17 MB/s - 1994
Ultra ATA (Mode 4); 33 MB/s - 1997
Ultra ATA/66 - brand new: 66 MB/s
SCSI - "standard" controller: 5 MB/s
SCSI - Fast: 10 MB/s
SCSI - Fast & Wide: 40 MB/s
SCSI - Ultra: 20 MB/s sustained, 80 MB/s burst rate

However, if you have multiple disks, then SCSI scores, because it is
capable of multi-processing - while one disk is doing a seek, another can
be doing a read. What this means to you and me is that SCSI has no
significant performance benefit for the "standard off the shelf" version
of either technology. In fact, it can even be slower, and is significantly
more expensive. However, for a machine which is especially used for
disk-intensive applications, and therefore has multiple drives, SCSI is
definitely better.

> Also make sure your machine isn't swapping to much. If you say you have
> not
> very much mem I expect this is your main problem.
> Squid keeps a lot in memory (and becomes very fast) but if it has to swap
> it
> becomes very slow...

VERY true. Remember that your RAM is somewhere between 300,000 and
1,000,000 times faster than the disk. If you are swapping to disk, then
this will REALLY slow you down. Depending on your OS and application, plan
on having 128 MB and up of RAM.

Up to a limit, the amount of RAM is much more important than the CPU speed.
For example, considering Windows 95 running typical office applications: A
Pentium 100 with 64 MB RAM is significantly faster than a 200 MHz Pentium
with 16 MB of RAM. Over ~55 MB it doesn't make a real difference in this
example. Other cases will require more RAM, e.g. a server of almost any


William Stucke
ZAnet Internet Services (Pty) Ltd
+27 11 465-0700
Received on Mon Oct 26 1998 - 02:37:10 MST

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