EIDE vs. SCSI?

EIDE vs. SCSI?

Post by allen kurt savegna » Thu, 21 Aug 1997 04:00:00



Hello,

   I have a Gigabyte GA-586DX Dual Pentium motherboard with the AIC 7880
onboard scsi controller.  This controller is rated at 20mb/s and I was
wondering if it would even be worth my while to go to a scsi drive?  The
controller takes 50 and 68pin connectors and I do have my Colorado T4000s
running fine.  I only have made full backups with it and haven't had to
do a restore yet.

  I am tied to Win 95 because my ISP uses a proprietary program and I
can't beat the $14.00 a month unlimited access.  Under Wintune,  I see
23 to 25mb/s transfer rates on the drives although I do not know if this
is some sort of an artifact.  My mobo does have busmastering and seems to
be working.  The disk transfer rates shot up 50% when I loaded the
busmastering drivers under 95.

  I am using kernel 2.0.30 and did compile in the busmastering drivers and
the machine seemed to run a bit faster.  Oh yes, I do know that only Linux
will use my second cpu and I did compile in SMP into the kernel with no
problem.  Any advice will be appreciated.  If I am not going to see much of
a performance increase under Linux, it might save me the cost of doing
an upgrade that wouldn't make much difference.

                                        Best regards,
                                        Kurt Savegnago

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EIDE vs. SCSI?

Post by Rod Smi » Thu, 21 Aug 1997 04:00:00


[Posted and mailed]



Quote:> Hello,

>    I have a Gigabyte GA-586DX Dual Pentium motherboard with the AIC 7880
> onboard scsi controller.  This controller is rated at 20mb/s and I was
> wondering if it would even be worth my while to go to a scsi drive?  The
> controller takes 50 and 68pin connectors and I do have my Colorado T4000s
> running fine.  I only have made full backups with it and haven't had to
> do a restore yet.

If you check the prices, you'll find that the price penalty for using
SCSI, given OTHERWISE IDENTICAL DRIVES, is quite small -- usually $20-$60
or so.  Given that, and given SCSI's various advantages, and given that
you've got the SCSI adapter, I'd say to go SCSI.  There are a couple of
caveats, though:

1) If you're on a shoestring budget, you CAN get cheaper EIDE drives,
   but they'll also not perform as well as the cheapest SCSI drives.  You
   get what you pay for.
2) I've heard that Adaptec plays games with its host adapters, and the
   Linux drivers don't always keep up with Adaptec's changes.  If you've
   run this host adapter fine with a tape backup, though, you've likely
   got a version that's not a problem one from the Linux point of view.

Quote:>   I am tied to Win 95 because my ISP uses a proprietary program and I
> can't beat the $14.00 a month unlimited access.

You may be able to.  Check out Boardwatch's ISP directory.  I found my
copy at a local bookstore, in the magazine section.  Most area codes have
at least a couple of ISPs selling service for as little as $10.  (Even if
a price in the magazine is a little higher than what you want to pay,
check their web page; they may have a discount for buying quarterly or
yearly.)

Quote:> Under Wintune,  I see
> 23 to 25mb/s transfer rates on the drives although I do not know if this
> is some sort of an artifact.

This sounds like an artifact.  Most drives are capable of only 3-6MB/s
sustained transfers.  Under Linux, try using dd to copy a large amount of
data to /dev/null, and time it; that'll give you a quick and easy
benchmark of raw drive performance.

--
Rod Smith                                 Author of:

http://php.indiana.edu/~rodsmith          "OS/2 Soundcard Summary"
NOTE: Remove "uceprotect" from address to e-mail me

 
 
 

EIDE vs. SCSI?

Post by Mark Ha » Fri, 22 Aug 1997 04:00:00


: If you check the prices, you'll find that the price penalty for using
: SCSI, given OTHERWISE IDENTICAL DRIVES, is quite small -- usually $20-$60

there are few drives like this.  the only one I've noticed recently
is the Quantum Fireball.  at the moment, I see only 3.2G for $220 or $315,
not a trivial difference.  you have to remember that regardless of whether
the mechanicals are identical, scsi is a relatively low-volume product,
and prices reflect this.

: 1) If you're on a shoestring budget, you CAN get cheaper EIDE drives,
:    but they'll also not perform as well as the cheapest SCSI drives.  You
:    get what you pay for.

this is only marginally true.  big/new eide disks deliver up to 11 MB/s.
yes, that's lower than the 15 or so that a Cheetah does, and even mundane
7200 rpm scsi's are a little faster than the top eides.  the price difference
is 200% or better, though!

: > Under Wintune,  I see
: > 23 to 25mb/s transfer rates on the drives although I do not know if this
: > is some sort of an artifact.

no, it's just stupidity.  current platters deliver around 8-15 MB/s.
any benchmark that indicates faster performance is simply broken.

: This sounds like an artifact.  Most drives are capable of only 3-6MB/s

few years ago, those were the numbers.  nowadays, all the highe-end eides
are sustaining 6-11 MB/s, and that's through the filesystem (ext2, 4k blocks,
busmastering).

: sustained transfers.  Under Linux, try using dd to copy a large amount of
: data to /dev/null, and time it; that'll give you a quick and easy
: benchmark of raw drive performance.

no.  raw device performance is deliberately unoptimized under Linux;
real filesystems are much faster.

in short, get SCSI if you're going to get >2 disks, other scsi devices
or must have Cheetahs.  otherwise, you'll save LOTS of money by buying
good (big/new) eide's and using the busmastering controller built in to
your motherboard.

regards, mark hahn.
--

                                        http://neurocog.lrdc.pitt.edu/~hahn/

 
 
 

EIDE vs. SCSI?

Post by Rod Smi » Fri, 22 Aug 1997 04:00:00




Quote:>: If you check the prices, you'll find that the price penalty for using
>: SCSI, given OTHERWISE IDENTICAL DRIVES, is quite small -- usually $20-$60

> there are few drives like this.  the only one I've noticed recently
> is the Quantum Fireball.  at the moment, I see only 3.2G for $220 or $315,
> not a trivial difference.

Granted, there are fewer and fewer drives available in both SCSI and EIDE
varieties.  I wasn't trying to claim there are tons of them.  As to the
price difference when they do exist, $95 was on the extreme end the last
time I went drive shopping.  A quick check at MegaHaus shows differences
that are higher (and they were higher the last time I shopped than the
time before that, so the difference is creeping up).

Quote:>: 1) If you're on a shoestring budget, you CAN get cheaper EIDE drives,
>:    but they'll also not perform as well as the cheapest SCSI drives.  You
>:    get what you pay for.

> this is only marginally true.  big/new eide disks deliver up to 11 MB/s.
> yes, that's lower than the 15 or so that a Cheetah does, and even mundane
> 7200 rpm scsi's are a little faster than the top eides.  the price difference
> is 200% or better, though!

I keep hearing people quote these phenomenal transfer rates, but I've yet
to see it myself, on ANY system.  Maybe I've just been seeing bum drives,
but the ones I've personally laid eyes on still max out at no better than
about 6MB/s, ON AVERAGE.  They'll do better than that on their best
tracks, of course, but worse on their worst tracks.  My sample does not
include the really high-end SCSI stuff; it's mostly mid-range to high-end
EIDE and low-end SCSI.

Your reply implies that price is or should be linearly dependant upon
speed -- that a drive that's twice as fast is worth precisely twice as
much money.  This is a subjective matter, though, and has to be determined
by the priorities of the individual making the purchase.  For some people,
price is far more important, while for others it's performance.

Quote:> in short, get SCSI if you're going to get >2 disks, other scsi devices
> or must have Cheetahs.  otherwise, you'll save LOTS of money by buying
> good (big/new) eide's and using the busmastering controller built in to
> your motherboard.

One of the reasons I like SCSI is that I, and I suspect most people who
use the same computer and upgrade it rather than junk it and buy a new
one, end up with multiple drives whether they intend it or not.
Therefore, somebody who buys a computer now with one drive may not get
much benefit from going SCSI, but in six months or a year, when it comes
time to upgrade the hard drive, the investment in SCSI WILL pay off.  It
may even pay off monetarily.  For instance, if somebody buys a computer
with a hard drive, CD-ROM, and internal Zip disk all on EIDE, and then
does the Right Thing and buys a tape backup (on EIDE, for the sake of
argument), then the only ways to upgrade the hard disk would be to replace
it or to buy an extra controller (which will difficult or possibly
impossible to configure, depending on other components).  With SCSI, those
five components can exist on a single chain, which can end up saving
money, or at least reducing the cost of the initial SCSI investment.

--
Rod Smith                                 Author of:

http://php.indiana.edu/~rodsmith          "OS/2 Soundcard Summary"
NOTE: Remove "uceprotect" from address to e-mail me

 
 
 

EIDE vs. SCSI?

Post by James Youngma » Fri, 22 Aug 1997 04:00:00


  allen>   I am tied to Win 95 because my ISP uses a proprietary
  allen> program and I can't beat the $14.00 a month unlimited access.

I'd be surprised if your ISP doesn't actually use PPP once all the
introductions are done.   Of course, you may need a highly specialised
chat script...

 
 
 

EIDE vs. SCSI?

Post by David L Pearc » Sat, 23 Aug 1997 04:00:00


There are a few other pluses to running SCSI, not just transfer rates.
With SCSI drives, commands can be queued so that the drives aren't
waiting for the turnaround time of the PC, because no matter how fast
your IDE driver is, it cannot totally eliminate this lag. You just
aren't going to see many heavy duty servers running IDE. A local
establishment runs a IDE based server, and its slow according to its
maintainers, very slow. Ballooning cable transfer rates will only grow
this delay (its constant actually except if processor speed increases)
in comparison to the amount of time the IDE interface is actually
transferring data. With the transfer rates currently found under IDE and
if some enterprising engineer came up with a way to maintain backwards
compatibility and implement a command queueing mode for IDE that could
coexist on the same drive inexpensively, he would be a rich engineer, as
IDE would be quiet superior to SCSI at that point, under the current
cabling. Otherwise I am sticking with SCSI . . .

--
David L Pearce - KF4MOK

 
 
 

1. IDE vs EIDE vs SCSI

Am I correct in thinking that SCSI disks under Linux perform way
better than IDE due to using DMA ? How about EIDE ?

Does the kernel do any disk caching beyond what is done on the disk drive;
ie. repeat read accesses to a file faster than single reads ? If so, is
this something that can be tuned?

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