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The NT cache or Win 95/98 is a write-through cache, that means each time
there is a modification to be written on a file, the write must be done on
the Hard Disk before the program can continue to do other tasks.
This has advantages : Data is theorically never lost on disk, I say
theorically because practically, it might be lost when there is a power
failure and the file was not closed.
But it has also a huge impact on overall performance. SuperCache NT from
eecsys (I have never seen another program doing that on NT/ Win 95/98, but
they might be some) can be configured as a write-back cache : That means
that data write is commited before it is actually written to the disk, it
will be written on background by a lazy process, approximately 1 to 5
seconds later. This leads to a tremendous performance enhancement of the
overall system.
There is one big disadvantage as well if you are not protected against power
failure, a lot of data might be lost (up to 10 seconds). Therefore, make
sure you use an UPS before activating a write-back disk cache, and
regularly do backups.
Anyway, for me, there is definetly no confidence in a PC without power
failure. data might be lost anyway, so there is not really a big difference
between write back and write through cache, if the system crashes due to a
power failure, there is a high risk you loose data anyway.
There might be also some specific hardware to do this, this is very common
on large computers like SUN enterprise 5000 and other unix serve boxes on
which the hard disk controller has a large disk cache backed up by a battery
able to keep data up to 1 year when power is lost, and data will be written
on disk as soon as power is back.
This technology is also available on PC as well, on RAID controllers like
MYLEX DAC 960 or DPT or other Hard disk controllers, it is more expensive
and requires ultra wide SCSI disks, the complete hard disk system price will
be around $3000-$4000, but can give access to other possible performance
enhancement like raid 0 (data stripping i.e. if you are using 4 disks, then
all 4 disks will be seen as one single large volume and data written will be
splitted on disks by blocks of 8 K, it is used mainly for SQL databases and
programs on which performance is critical. I do not believe it would worth
the price unless you have a very large portofolio on which one day off would
result in a potential large loss. But in that case, I believe the smartest
thing would be to have a spare PC used as backup of the regular PC.
For backups : personally as I upgraded my PC, I changed my disk for a larger
one and I used my old disk as a backup disk on which I store disk images. It
is really faster than a tape backup (approx 5 minutes to do the backup of
the full disk).
-----Original Message-----
From: owner-metastock@xxxxxxxxxxxxx
[mailto:owner-metastock@xxxxxxxxxxxxx]On Behalf Of John Sellers
Sent: Monday, June 14, 1999 6:49 PM
To: 'metastock@xxxxxxxxxxxxx'
Subject: RE: Off Topic: Choice of Processor
This approach sounds interesting but would you please explain more about
the cache. I am aware that my computer has a swapping file which is managed
in size by the Windows system program or may be set to some amount of fixed
memory for each of the minimum and maximum values. I am aware that setting
both max and min values to one value a sufficiently high value for ones
programs; this approach I found from my experience achieved an increase in
operationally speed. I believe it may have been accomplished because of
faster data transfers.
Is this cache memory something different? I believe all of our group should
comprehend computer functionality because most of us at some time in the
future shall be considering purchase of an improved computer .
-----Original Message-----
From: Laurent GITTLER [SMTP:lgittler@xxxxxxxxxxx]
Sent: Monday, June 14, 1999 8:16 AM
To: metastock@xxxxxxxxxxxxx
Subject: RE: Off Topic: Choice of Processor
Here is my personal thoughts, it won't be what people will generally say,
but it is quite easy to find out if you are using several OS and compare
them, ie. Win 95&NT vs. Linux).
I am not using MS PRO, and what I do are genrally explorations on 9000
stocks to detect some patterns, divergence and so on on all stocks. What I
want is those explorations to be run as fast as possible, and I want smotth
screen output as well.
What I found is is somehow amazing : The CPU power on WIN 95/NT is not the
key element of the overall PC performance. Memory and hard disk have the
most impact on response time on explorations.
I have a K6-233 I bought a year and a half ago (so said "old CPU"), NT4
workstation. What I monitored is bottleneck is made on disk activity while
exploring. I switched from an average exploration time of 17 minutes to 6
minutes just by using a good hard disk write behind cache program. I made
test on a PII 350 MHz, NT4, 256 Mb RAM without hard disk write back cache,
and again, I got explorations of 16 minutes.
More than 32 Mb of my 96 Mb Memory are dedicated to cache. I consider
upgrading my system to a Celeron 350 MHz or K6-2 350 or whatever, but
emphasize the PC upgrade on memory (256 K RAM or 512 Mb RAM) and real fast
hard disks.
I wish I had 1 Gb RAM and then I would do MS explorations in RAM disk with
background writes to the Hard disk, I am sure it will really give blasting
performance.
So my advise would be : make sure you have the best hard disk, or even
consider RAID 0 disks (stripping) with write back cache. But all I say is
for explorations (i.e regularly scan the databse for patterns and so on).
My
problem might be totally different from yours.
Laurent GITTLER
-----Original Message-----
From: owner-metastock@xxxxxxxxxxxxx
[mailto:owner-metastock@xxxxxxxxxxxxx]On Behalf Of Essan Soobratty
Sent: Tuesday, June 15, 1999 3:36 PM
To: metastock@xxxxxxxxxxxxx
Subject: Off Topic: Choice of Processor
Hi,
I am about to upgrade my current PC which is an NEC PII 233mhz. I am
not an expert when t comes to hardware and therefore seek views as to an
appropriate upgrade.
Its main use would be for running metastock pro, excel, word, netscape
etc and it would be part of a LAN network. I don't think I would be
using it for any heavy duty graphics.
Browsing the shelves of Comp-USA it looks like my choices are between an
Intel Celeron, PII or PIII. Can anyone give some suggestions and in
particular describe the differences between the 3 processors? Whatever
the choice, I would have a minimum of 64meg or RAM and would prefer to
use win95.
Also as a bechmark, which Celeron chip would be the equivalent to my
current PII 233mhz?
Email direct if you prefer. Thanks in advance.
Essan Soobratty.
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