Re: HDD + FD info

From: Marc van Selm <>
Date: Fri, 20 Mar 1998 08:33:48 +0100

At 11:02 AM 3/20/98 +1000, Dancer wrote:
>Michael Samuel wrote:
>> On Thu, 19 Mar 1998, Bill Wichers wrote:
>> > I'm doing some research into building a series of smaller caches (for
>> > schools mainly), and the idea is too keep costs down as much as possible.
>> > My question:

>> I haven't done any production level tests, but I can tell you, if you use
>> Linux, to get the performance required for a proxy cache to be worth
>> having on IDE (nothing does real UDMA anyway yet), you'll need so much RAM
>> that it would be the same cost to just buy a SCSI hard disk :-)
>> This wasn't even on a production machine (just a home test)...
>I think that's subjective. It depends on the number of clients,
>available bandwidth, number of requests, etc, etc, etc. We use IDE
>drives in all our squid caches (we have 9 in toto), and in most cases we
>choose IDE drives with slower seek times. At the available
>input-bandwidth, the faster drives just aren't worth it, since even the
>slowest of our IDE drives will still outperform our uplink by a
>significant factor.
>It starts to make a difference when you have many clients hammering away
>at hits. We deployed satellite caches for that, which was a wise
>decision anyway, given the intermediate links. All in all, the users are
>very happy with the performance, as opposed to living without.

I fully support "Dancers" statement. OK SCSI is faster but if the link or
the money is a bottleneck it doesn't make sense. Also there are some nice
fast IDE's on the market right now. Only make sure you have a fast chip set
(and OS support) so you get the most of it.

As a comparison: I'm running an Sun Ultra-1 with 2x 4GB ultra-wide SCSI for
cache. Average available link speed (shared link with priority queueing) is
150kbps (peak 384kbps). In this setup the disks are only 20% active and the
response times of the cache good. We have about 200 users with internet
access. This suggests that for smaller caches there is some room to reduce
the hardware performance in order to save a buck. (even in our case the
proxy is a bit over designed)

If you have the money why not get the best but if you don't ....



Marc van Selm
NATO C3 Agency
Communication Systems Division, A-Branch

   "Nobody will ever need more than 640k RAM!"
                           -- Bill Gates, 1981
   "Windows 95 needs at least 8 MB RAM."
                           -- Bill Gates, 1996
   "Nobody will ever need Windows 95."
                           -- logical conclusion
Received on Thu Mar 19 1998 - 23:43:59 MST

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