Building a new system: SCSI or IDE?

[Jonathan Sachs]

I'm assembling a new system in a couple of months, and am facing the
old dilemma: SCSI or IDE disks?

I have traditionally insisted on SCSI disks because they're faster and
more reliable. Lately I've been having some hearing problems, though,
and the drive noise is bothering me. Thus I'm motivated to use IDE
drives in my next system if I can do so without too much compromise.

What about performance? If I run two or or three disk-intensive
applications under Windows, will there be much practical difference
between a pair of fast Ultra320 drives and a pair of fast IDE drives?

I will have at least three IDE devices: two hard disks and a CD/RW or
DVD drive. I'm assuming that each device should go on a dedicated
channel. If so, should I get a mainboard with four IDE channels built
in, or will an add-on adapter work equally well?

What about reliability? Are modern IDE drives reliable enough for all
practical purposes? (I define this to mean a negligible chance of
failure over a system life of three years, with the drives running
almost constantly.) Are there any popular brands or models which have
particularly good or bad reputations?

My mail address is jsachs177 at earthlink dot net.

 

[Bob WIllard]

I'm assembling a new system in a couple of months, and am facing the
old dilemma: SCSI or IDE disks?

I have traditionally insisted on SCSI disks because they're faster and
more reliable. Lately I've been having some hearing problems, though,
and the drive noise is bothering me. Thus I'm motivated to use IDE
drives in my next system if I can do so without too much compromise.

What about performance? If I run two or or three disk-intensive
applications under Windows, will there be much practical difference
between a pair of fast Ultra320 drives and a pair of fast IDE drives?

I will have at least three IDE devices: two hard disks and a CD/RW or
DVD drive. I'm assuming that each device should go on a dedicated
channel. If so, should I get a mainboard with four IDE channels built
in, or will an add-on adapter work equally well?

What about reliability? Are modern IDE drives reliable enough for all
practical purposes? (I define this to mean a negligible chance of
failure over a system life of three years, with the drives running
almost constantly.) Are there any popular brands or models which have
particularly good or bad reputations?

My mail address is jsachs177 at earthlink dot net.

I suggest neither SCSI nor IDE (meaning PATA) HDs, but SATA. SATA
is the successor to PATA, with better performance and better cabling.
I think that a good current choice would be SATA for HDs and PATA
for DVD/CD stuff.

Modern HDs have MTBFs, regardless of bus, on the order of 10 years.
What you get in practice depends a lot on the environment; pay real
attention to cooling (air flow) and make sure that your power supply
choice is based on attributes other than price.

 

[Rod Speed]

I'm assembling a new system in a couple of months,
and am facing the old dilemma: SCSI or IDE disks?

SCSI has basically passed its useby date for all except the most
demanding situations. Basically lousy value for money now.

I have traditionally insisted on SCSI disks because they're faster and
more reliable. Lately I've been having some hearing problems, though,
and the drive noise is bothering me. Thus I'm motivated to use IDE
drives in my next system if I can do so without too much compromise.

What about performance? If I run two or or three disk-intensive
applications under Windows, will there be much practical difference
between a pair of fast Ultra320 drives and a pair of fast IDE drives?

I doubt you'd be able to pick the difference in a
proper double blind trial with your ears plugged.

I will have at least three IDE devices: two hard disks
and a CD/RW or DVD drive. I'm assuming that each
device should go on a dedicated channel.

No need.

If so, should I get a mainboard with four IDE channels
built in, or will an add-on adapter work equally well?

2 channels will be fine.

What about reliability? Are modern IDE drives reliable
enough for all practical purposes? (I define this to mean
a negligible chance of failure over a system life of three
years, with the drives running almost constantly.)
Yep.

Are there any popular brands or models which
have particularly good or bad reputations?

I like the WDs myself. I avoid the Hitachi/IBMs because
of the atrocious record they got with relatively recent
drives and the fact that they have a lousy RMA system.

Best to avoid the Seagate Barracudas in your situation
because they have chosen to disable AAM because of
some stupid claim about patent infringement. That means
that the currently buyable drives arent that quiet anymore.

 

[Folkert Rienstra]

I suggest neither SCSI nor IDE (meaning PATA) HDs, but SATA.

Well, that certainly solves the seperate channels problem.

SATA is the successor to PATA, with better performance

Potentially better performance. Currently there is only one drive that act-
ually makes use of it. Others are just PATA drives with a SATA interface.

 

[Folkert Rienstra]

Hi Johnathan:

Although SCSI has always been considered superior, IDE performance
has improved drastically in recent years,

So has SCSI's.

 

[Folkert Rienstra]

I'm assembling a new system in a couple of months, and am facing the
old dilemma: SCSI or IDE disks?

I have traditionally insisted on SCSI disks because they're faster and
more reliable. Lately I've been having some hearing problems, though,
and the drive noise is bothering me. Thus I'm motivated to use IDE
drives in my next system if I can do so without too much compromise.

What about performance? If I run two or or three disk-intensive
applications under Windows, will there be much practical difference
between a pair of fast Ultra320 drives and a pair of fast IDE drives?

Should be, given that SCSI still has the beter access time and IO/s.

I will have at least three IDE devices: two hard disks and a CD/RW or
DVD drive. I'm assuming that each device should go on a dedicated
channel. If so, should I get a mainboard with four IDE channels built
in, or will an add-on adapter work equally well?

There probably ain't a difference unless the extra
channels are on the MoBo chipset. Still, with 2 harddrives
you probably won't spring the PCI bus 132MB/s limit anyway.

 

[Jonathan Sachs]

A "Quality" high end SCSI hard drive will last longer
under long term disk-intenive (24 hour a day) work.
But you are paying a lot more money.

The drives will be spinning all the time, but since this is a
workstation, they will not be seeking all the time. When I mentioned
"disk-intensive applications," I was thinking of my need for
performance during short periods of high activity, not the effects of
disk activity on the drives.

It never occurred to me that pounding the disk would actually wear it
out. I'm accustomed to thinking that drive life is dependent on
power-up time and the operating environment, and on power-up/down
cycles. Am I being too simplistic?

I would get a motherboard with the built-in Raid controller (only about $20
more).
Put the ATA/EIDE Boot hard drive on the Raid controller.

An interesting possibility, which I hadn't considered. It brings a
couple of questions to mind.

First, will I pay a performance penalty? I investigated RAID several
years ago, and learned that there was a substantial performance
penalty. Even with RAID 0 there was a penalty if the drives were not
synchronized (and IDE drives did not have the hardware necessary to do
that).

Second, what about noise, heat, and space requirements? This would
increase the number of drives in my system from 2 to 4, presumably
doubling all of those factors. Might I not find four IDE drives to be
nearly as noisy as two SCSI drives, or even noisier?

My mail address is jsachs177 at earthlink dot net.

 

[Tod]

The drives will be spinning all the time, but since this is a
workstation, they will not be seeking all the time. When I mentioned
"disk-intensive applications," I was thinking of my need for
performance during short periods of high activity, not the effects of
disk activity on the drives.

It never occurred to me that pounding the disk would actually wear it
out. I'm accustomed to thinking that drive life is dependent on
power-up time and the operating environment, and on power-up/down
cycles. Am I being too simplistic?

So you are just doing normal disk activity.
I think most people would agree that heat is the drive killer.

An interesting possibility, which I hadn't considered. It brings a
couple of questions to mind.

First, will I pay a performance penalty? I investigated RAID several
years ago, and learned that there was a substantial performance
penalty. Even with RAID 0 there was a penalty if the drives were not
synchronized (and IDE drives did not have the hardware necessary to do
that).

A 7200RPM ATA/EIDE will have close to the same performance
as a SCSI 7200 drive
Invest in a fast processor and lots of memory.

 

[Rod Speed]

That seems to require some explanation.

The short story is that its only simultaneous ops on a pair of drives
that benefits from having that pair on a separate channel. Thats
pretty uncommon in practice. The most common real world situation
where thats seen is when ghosting one drive to an image file on
another drive and even then, the speed of that operation is
dominated by the compression time if compression is used.

Even when say burning a CD from a hard drive, the speed
of the entire operation is mostly determined by the speed of
the burner which is much less than the speed of a hard drive.

I said "I'm assuming" because I know that an IDE
channel can perform only one operation at a time.

Yes, but the modern reality is that you dont often use two drives
literally simultaneously. And you never use 4 drives simultaneously,
so there isnt any need for them all to have their own channel.

Even SCSI doesnt allow the use of all 4 drives simultaneously anyway.

Thus if two devices share a channel, any
operation on one device will lock out the other.

Only if both are being used at once.

Thus if a DVD drive is seeking, for example, a
read or write request on the hard disk will jolly well
have to wait until it's done. Is this no longer true?

Its still true. But you dont normally want to use them
simultaneously and when you do, say with an install
from the drive to a hard drive, the fact that the hard
drive has to pause occassionally while the DVD
drive head seeks isnt normally a real problem.

 

[Bob WIllard]

Even SCSI doesnt allow the use of all 4 drives simultaneously anyway.

Sure it does. SCSI allows all drives to be used simultaneously;
up to 7 HDs on a narrow bus and up to 15 HDs on a wide bus. E.g.,
SCSI allows the initiator (the Host Adapter) to issue a read command
to each target (HD) and then disconnect from the SCSI bus; each HD
may then, concurrently, do the seek, then read data from the platter
into its buffer, and reconnect only when it is ready to copy data
into host RAM. This capability is one reason why it makes sense to
use a 320 MB/s (U320) version of SCSI to attach HDs which have STRs
of less than a quarter of the bus data rate.

Moreover, with command queuing, a bunch of read commands can be
issued to each HD, and each HD can execute them out-of-order and
briefly re-occupy the SCSI bus to do the actual data transfer.
And yes, it works the same way for writes and for mixtures of
reads and writes.

I am not claiming that WinWhatever takes full advantage of the
capabilities of SCSI, but there are grown-up OSs which do.

 

[Folkert Rienstra]

No where near to the same extent.

Ofcourse it has.

From a performance point of view, now that
you can use IDE RAID, SCSI doesn't offer much more.

SCSI RAID, obviously.

From a reliability point of view SCSI is obviously still ahead,

Nope. There is where ATA indeed made good.

but IDE has come a long way. Given the substantial price dif-
ference, you have to consider whether SCSI is really worth it.

Ofcourse, but that goes for every component on the system.

For a home system like the OP is talking about, though,
SCSIs negatives (namely price) far outweigh it's benefits.

Same can be said for processors, perhaps even more so.
However, processors are much sexier, for some stupid reason or other.

I don't think he meant standard in any official sense

IDE always was standard on a PC, it's not 'becoming' standard.
SCSI always has been for Servers and highend Workstations.

(ie. that it is planned to phase out SCSI and replace it with IDE),
but SCSIs market is certainly shrinking.

It isn't. Maybe it will with SATA and SAS on the horizon.
However for SATA to become external you need SAS.

I would strongly consider using IDE drives for some servers these days,

That's entry level server.

and I'm not alone.

IDE is fine for central backup. It isn't for multiuser/multitasking.
IDE is a goner. SATA *may* take inroads in the higher end workstation
business and parts of the server business by introducing professional
grade SATA drives like the current WD RAPTOR.

SCSIs niche will continue to be infiltrated by IDE, meaning that
prices for SCSI will rise and support and innovation will decrease.

IDE is nearly dead, SCSI will soon be. SAS and SATA will take over.
When SATA starts to invade the server business too much, SAS will
have to come down in price. However, if SAS can sustain market share
by taking over some Fiber Channel business, that may not happen.

 

[Rod Speed]

Rod Speed wrote:

Sure it does. SCSI allows all drives to be used simultaneously;

Wrong. You cant simultaneously transfer data from all
drives literally simultaneously, there is still only one bus.

What SCSI can do is use the bus for another drive when
one of them is seeking etc. Thats not the same thing as
simultaneous data transfer from all drives at once.

up to 7 HDs on a narrow bus and up to 15 HDs on a wide bus.
E.g., SCSI allows the initiator (the Host Adapter) to issue a
read command to each target (HD) and then disconnect from
the SCSI bus; each HD may then, concurrently, do the seek,
then read data from the platter into its buffer, and reconnect
only when it is ready to copy data into host RAM.

Yes, but that is NOT simultaneous data transfer.

This capability is one reason why it makes sense to use
a 320 MB/s (U320) version of SCSI to attach HDs which
have STRs of less than a quarter of the bus data rate.

Separate issue entirely.

Moreover, with command queuing, a bunch of read commands can
be issued to each HD, and each HD can execute them out-of-order
and briefly re-occupy the SCSI bus to do the actual data transfer.

Separate issue entirely. And command queuing
isnt just available with SCSI anyway.

And yes, it works the same way for writes
and for mixtures of reads and writes.

Sure, but you never get simultaneous data transfer from
multiple drives, they still have to do that sequentially.

IDE is actually better with the usual 2 controllers in that respect.

I am not claiming that WinWhatever takes full advantage of the
capabilities of SCSI, but there are grown-up OSs which do.

No OS can achieve simultaneous data transfer
with multiple SCSI drives on a single bus.

 

[Rod Speed]

I think your entire argument assumes that the
computer is being used to do one thing at a time

Nope. What matters is how often there is significant
drive activity on more than one drive at a time.

And SCSI cant transfer data simultaneously from more
than one drive at a time anyway, ALL it can do is allow
one drive to seek while another is transfering data etc.

-- something which, for me, is emphatically not true.
It's common for me to have a dozen windows open at once,
and two or three applications actively working simultaneously.

Yes, but what matters is how intensively each of those apps
is using the drive(s) its using. With say burning a CD from the
hard drive, the app normally does that sequentially. And what
matters is whether the app can get frequent enough access
to the hard drive to get enough data to keep the burner happy
when that output rate is MUCH lower than the hard drive.

What if I'm writing a document while referring
to information on a DVD ROM or CD ROM?

The app thats used to write the document is hardly ever
using the hard drive, just when you save the document
occassionally. So that app isnt using the hard drive and the
ROM drive literally simultaneously in a data transfer sense.

Since I have carpal tunnel syndrome, I depend
on speech recognition software to write, and it is
quite disk intensive (as well as CPU intensive).

Sounds like its rather badly design or
you dont have enough physical ram.

In that situation, sharing an IDE channel between
the DVD/CD drive and one of my hard disks could
be like trying to eat dinner with one hand.

Nope, nothing like it in fact. And you just have the hard
drive on a different channel to the DVD/CD drive anyway,
no need for a separate channel for every one of the drives.

And SCSI cant do simultaneous data transfers
anyway, in some ways its even worse with just
one bus instead 2 with standard IDE.

The only real advantage SCSI has is that a slow seeking
drive can disconnect from the bus while its seeking etc.
IDE achieves an even better result with 2 channels
because there isnt even any need to disconnect.

 

[Lifelong US Citizen]

Buy some "used" SCSI drives on EBay. Lots of good values for U160
drives, since people seem to be upgrading their servers to U320.

Also, another point for using at least some SCS in your system is that
good tape backup units are all SCSI-based.

I should also add that I have never had a SCSI drive fail, except one
Quantum drive way, way back when.

And modern SCSI drives are very quite also.

 

[Jonathan Sachs]

And modern SCSI drives are very quite also.

Can you provide specifics?

I'm currently using two 36 GB Ultra160 drives from Seagate. One is
about a year old, the other, probably three years old. I believe their
idle noise level was rated around 3.4 bels, and I don't know of any.
standard SCSI drives which are much quieter than that. I find the
noise very bothersome.

My mail address is jsachs177 at earthlink dot net.

 

[Simon]

A quick analogy for you:

IDE 4 cylinder. SCSI V8.

They both do the same job, but you know that the SCSI will go on for ever,
and not wear itself out.

Simon

Oh yes, we still sell hundreds of SCSI drives per month.

 

[Simon]

50Gb $45US - Lousy value? Its where you shop

SCSI has basically passed its useby date for all except the most
demanding situations. Basically lousy value for money now.



I doubt you'd be able to pick the difference in a
proper double blind trial with your ears plugged.


No need.


2 channels will be fine.


I like the WDs myself. I avoid the Hitachi/IBMs because
of the atrocious record they got with relatively recent
drives and the fact that they have a lousy RMA system.

Best to avoid the Seagate Barracudas in your situation
because they have chosen to disable AAM because of
some stupid claim about patent infringement. That means
that the currently buyable drives arent that quiet anymore.

 

[Rod Speed]

50Gb $45US - Lousy value?

Pity about the price of IDE, salesfool.

Its where you shop

Usual salesfool liar.

You obviously flogged used cars previously.

 

[Gareth Church]

A quick analogy for you:

IDE 4 cylinder. SCSI V8.

A quick analogy, and a worthless one (like most are). I've heard the same
analogy used in the Mac vs PC debate. It's says nothing. It's the sort of
thing people say when they have a strong opinion, but can't come up with any
actual reason why they feel the way they do.

They both do the same job, but you know that the SCSI will go on for ever,
and not wear itself out.

Your hyperbole aside, I do agree that on the whole SCSI is more reliable
than IDE.

Really, if that is your opinion why didn't you just say it? The analogy was
dumb, and isn't analogous at all. The difference between a 4 cylinder engine
and a V8 isn't how long they last, it's power. If you want to find something
analogous to that in the hard drive world (which is a pointless thing to
do), it would be sustained transfer rate, not reliability.

Gareth

 

[Joshua P. Hill]

Mindlessly superficial.

Takes one to know one, I guess.

Mindlessly superficial.

Yeah, Roddy, we're really convinced when you start to repeat yourself.
Reminds us of our eight-year-olds in a snit.



Josh