Disk transfer rates

[Crouchez]

I'm just looking at data transfer speeds on various types of hdd. I know
it's a general question but is SATA the fastest? What about the USB drives?
Are they faster at reading and writing than standard PATA drives?

 

[Grinder]

I'm just looking at data transfer speeds on various types of hdd. I know
it's a general question but is SATA the fastest? What about the USB drives?
Are they faster at reading and writing than standard PATA drives?

USB Drives are in fact SATA or PATA drives in a box with an ATA-to-USB
interface adapter. The max transfer rate of USB is significantly lower
that the max transfer rate of a contemporary SATA/PATA drive, and will
be the limiting factor. Moreover, it's been my practical experience
that the USB interface cannot sustain anything close the max transfer rate.

Most PATA drives available now are either ATA-100 or ATA-133, meaning
max transfer rates of 100 and 133 MB/s respectively. SATA-1 tops out at
150 MB/s. The limiting factor, though, appears to be the internal
mechanism of the drive, and not the interface. Western Digital and
Seagate, for instance, remain competitive with their ATA-100 offerings
while other manufacturers have fixed upon ATA-133.

In short: Unless you need the portability of a USB drive, go with an
internal one.

 

[kony]

I'm just looking at data transfer speeds on various types of hdd. I know
it's a general question but is SATA the fastest?

Sometimes yes, sometimes no. The predominate factor is
which specific drive you choose for comparison. However,
given equal drives the SATA interface does have a minor
performance advantage.

What about the USB drives?

There are no USB drives, only SATA or PATA drives bridged
over to USB interface. Since USB is inherantly slower from
both a total throughput and latency factor, they are the
worst alternative if performance matters (but USB IS
convenient sometimes).

Are they faster at reading and writing than standard PATA drives?

You seem to be trying to compare out of context, which is
seldom a good idea, things like whether either controller is
sitting on the PCI bus tend to matter more than which (SATA
or PATA) you are using.

 

[GT]

I'm just looking at data transfer speeds on various types of hdd. I know
it's a general question but is SATA the fastest? What about the USB
drives? Are they faster at reading and writing than standard PATA drives?

You have slightly jumbled terms...

SATA and IDE are the interface type, not the drive transfer speed. PATA (or
IDE or EIDE) has a maximum throughput of 133MB/s. SATA has a maximum
throughput of 150MB/s. SATA II has a maximum throughput of 300MB/s.

The speed of the hard disk has nothing* to do with the interface type and
modern hard disks can sustain around 70MB/s, so any interface type is more
than enough headroom for hard disk.

You may be able to measure a performance improvement with a SATA transfer as
the burst rate is higher (can transfer data to the hard disk's cache at the
maximum bus speed), however in reality, the performance improvement will be
measured in thousandths of a second!

*The interface type doesn't directly affect the speed of a drive, but
'things' can be optimised for a particular interface type, so performance
differences, whilst slight, can be observed.

 

[Crouchez]

cheers for the info. am just woindering whether it's worth upgrading to a
sata motherboard

 

[kony]

cheers for the info. am just woindering whether it's worth upgrading to a
sata motherboard

For SATA alone, no.

We can't say whether any other features are worthwhile, you
don't mention the specifics. Generally speaking, upgrading
a motherboard while keeping same CPU and memory is never a
good upgrade.

 

[Crouchez]

For SATA alone, no.

We can't say whether any other features are worthwhile, you
don't mention the specifics. Generally speaking, upgrading
a motherboard while keeping same CPU and memory is never a
good upgrade.

what about a SATA drive with a USB interface? will that be faster than a
standard 133Mb PATA?

 

[Crouchez]

For SATA alone, no.

We can't say whether any other features are worthwhile, you
don't mention the specifics. Generally speaking, upgrading
a motherboard while keeping same CPU and memory is never a
good upgrade.

But I can almost triple the data transfer speed if I upgrade to a SATA
board?

 

[kony]

what about a SATA drive with a USB interface? will that be faster than a
standard 133Mb PATA?

No, it will be much slower if the drives themselves are
otherwise equivalent.

 

[kony]

But I can almost triple the data transfer speed if I upgrade to a SATA
board?

This has already been covered, no you cannot because the
drive itself does not transfer at that SATA300 speed- that
is only a theoretical upper limit except for very brief
cached transfers. The specific drive you choose matters
more than which interface it uses when considering PATA or
SATA. Of the 3 busses, only USB is so slow that it will
always be slower with any semi-modern drive.

 

[GT]

cheers for the info. am just woindering whether it's worth upgrading to a
sata motherboard

If you really want SATA - spend a few poinds on a PCI SATA card, but you
will be dissappointed with the performance difference. Any new hard disk
will be faster than one from over a year ago, regardless of the interface
type. The only thing you gain with SATA is a little more future proofing.

 

[GT]

But I can almost triple the data transfer speed if I upgrade to a SATA
board?

NOOOOOOO you don't - you increase the maximum speed limit from 133 to 300,
but the car can still only manage 70!

If you buy a faster computer you can't type any faster

If you buy a bigger mouse, the cursor won't move any faster

If you buy a wider drive, you can't park any faster

 

[Crouchez]

NOOOOOOO you don't - you increase the maximum speed limit from 133 to 300,
but the car can still only manage 70!

If you buy a faster computer you can't type any faster

If you buy a bigger mouse, the cursor won't move any faster

If you buy a wider drive, you can't park any faster

so under what conditions can 300mb/sec be achieved?

 

[kony]

so under what conditions can 300mb/sec be achieved?

None.

You might get fairly close to that on a short burst,
directly accessing the onboard cache memory. Benchmarks
show this is only of minor benefit in most uses (versus a
PATA133 bus).

If your motherboard can natively support SATA150 or 300, go
ahead and get an SATA drive as it is the forward looking
tech and will be easier to replace later if/when it fails.

 

[kony]

If you really want SATA - spend a few poinds on a PCI SATA card, but you
will be dissappointed with the performance difference. Any new hard disk
will be faster than one from over a year ago, regardless of the interface
type. The only thing you gain with SATA is a little more future proofing.

Running an SATA drive from a PCI SATA card is slower than
SATA via a southbridge or PATA via southbridge. Combine
that with the potential for other PCI devices to need
concurrent bandwidth and a PCI controller is best avoided
unless the system is of a limited and special purpose.

 

[GT]

so under what conditions can 300mb/sec be achieved?

Here's an example: If you were saving a 100MB file from memory direct to
hard disk, then the "ideal world, lab conditions, no virus software, nothing
else running, nothing else considered" transfer times would look something
like this:

The first 8MB (disk cache size) would potentially travel at the speed of the
bus (but in reality would probably be slower):

PATA - first 8MB at 133MB/s = 0.06 seconds
SATA - First 8MB at 150MB/s = 0.05 seconds
SATA II - First 8MB at 300MB/s = 0.03 seconds

As the drive cache is full, the remaining 92MB would transfer at 60-70MB/s.
ie. the disk's max speed, which is around 1.31 to 1.53 seconds, so total
transfer times for this file looks like this

PATA = 0.06 + 1.31 to 1.53 seconds = 1.37 to 1.6 seconds
SATA = 0.05 + 1.31 to 1.53 seconds = 1.36 to 1.58 seconds
SATA II = 0.03 + 1.31 to 1.53 seconds = 1.33 to 1.56 seconds

In other words the above transfer would be something like 2.5 to 2.9 %
faster using SATA II over PATA (EIDE133). A scientifically measurable, but
unnoticable difference!

 

[GT]

Running an SATA drive from a PCI SATA card is slower than
SATA via a southbridge or PATA via southbridge. Combine
that with the potential for other PCI devices to need
concurrent bandwidth and a PCI controller is best avoided
unless the system is of a limited and special purpose.

Kony, what speed / throughput is the PCI bus? With no other PCI cards would
a SATA II PCI card have to contend with anything else - USB or any other
area?

 

[kony]

Kony, what speed / throughput is the PCI bus? With no other PCI cards would
a SATA II PCI card have to contend with anything else - USB or any other
area?

It depends on the board, what else is on the PCI bus.
Obviously anything plugging into a PCI slot would be, as
well as some discrete add-on chips you may find on boards
for additional functionality.

PCI bus throughput is up to 133MB/s but there's overhead
that will practically reduce that to (overgeneralizing,
since we'd have to benchmark a specific card to nail down a
number) around 110MB/s alone. That's with a board having a
chipset fairly efficient at PCI, some (like several past
generations of Via chipsets) weren't so efficient and might
be under 90MB/s and become problematic if there are any
other PCI devices in use like a sound card or gigabit
ethernet.

 

[Plato]

I'm just looking at data transfer speeds on various types of hdd. I know
it's a general question but is SATA the fastest? What about the USB drives?
Are they faster at reading and writing than standard PATA drives?

USB drives are always slower.