put 2 CDRW drives on same or different ATAPI channels?

[Timothy Daniels]

I've read that there is an advantage to putting hard drives
on separate ATA channels to avoid contention for the
channel when copying files from one HD to the other HD
(such as when doing backups). Is such a configuration
also advantageous for CD drives when copying from one
drive to the other on the fly?


*TimDaniels*

 

[Rod Speed]

I've read that there is an advantage to putting hard
drives on separate ATA channels to avoid contention
for the channel when copying files from one HD to
the other HD (such as when doing backups).

Can be a bit pointless even with those,
particularly if you compress the image, that
can swamp the separate channel effect.

And you dont normally sit around twiddling your thumbs
waiting for it to happen anyway, so its rather academic
if it ends up saving say 20% of the time.

Is such a configuration also advantageous for CD drives
when copying from one drive to the other on the fly?

Nope, because the speed of that particular operation
depends entirely on the time taken to burn the CD, the
speed of the memory to drive transfer is irrelevant.

 

[Timothy Daniels]

Timothy Daniels asked:

Can be a bit pointless even with those,
particularly if you compress the image, that
can swamp the separate channel effect.

And you dont normally sit around twiddling your thumbs
waiting for it to happen anyway, so its rather academic
if it ends up saving say 20% of the time.

I plan to image one drive on the other for periodic
backups, and I figured the time to image the drive
might be reduced by putting them on separate channels.
20% time savings might be worth the small effort now.

Nope, because the speed of that particular operation
depends entirely on the time taken to burn the CD, the
speed of the memory to drive transfer is irrelevant.

Ah! Thanks for the insight.


*TimeDaniels*

 

[Folkert Rienstra]

I plan to image one drive on the other for periodic
backups, and I figured the time to image the drive
might be reduced by putting them on separate channels.
20% time savings might be worth the small effort now.

On pure seqential reads and writes the effect is minimal to none.

Depends on what process is used for the copying.

Nope, only with a steady supply of source data.
It very much depends on how the copying process is done (image or
file) whether that is the case. When the source data is read nonse-
quential, as with file copying, caching and/or buffering are of little
use and the writing process stops and has to pick up again after that.

the speed of the memory to drive transfer is irrelevant.

You don't say ... , .... isn't that a (irrelevant) fact.

Ah! Thanks for the insight.

What insight?

 

[Rod Speed]

Rod Speed wrote

I plan to image one drive on the other for periodic backups,
and I figured the time to image the drive might be reduced
by putting them on separate channels. 20% time savings

You'd have to try that, you may find there isnt much
in it, particularly when the image files are compressed.

While you can claim that you might as well use the more
efficient config, that can get awkward cabling wise and
its not worth farting around if you dont get a significant
improvement in image creation time. And like I said, the
time is rather academic most of the time anyway, because
you dont wait for it to happen if you have any sense.

might be worth the small effort now.

I doubt it except for the anal. The short story is that the
most mechanically convenient arrangement is usually best.

 

[Folkert Rienstra]

I've read that there is an advantage to putting hard drives
on separate ATA channels to avoid contention for the channel

when copying files from one HD to the other HD (such as when doing backups).

There is no contention in that case.
Well, it actually depends on what you call (serious) contention:

The biggest contention exists with reads to both drives *or* a write
to one drive that is started _after_ a read to the other and it doesn't
have that data cached.

That doesn't happen in the 'copy drive' case.

The smaller contention exists in the fact that you can only issue the
next read to the source drive *after* the write to the destination drive.
That only has an effect when the source drive is read non sequential.
When read sequential the source drive caches ahead when the destination
drive is writing so the data is available as soon the command comes in.

Is such a configuration also advantageous for CD drives when copying from one
drive to the other on the fly?

Same applies here but the chance of the copying (not imaging)
being sequential is much bigger than it is with harddrives.
Image copying is not a problem at all.

 

[troll shafter]

Some pathetic excuse for a troll claiming to be
just the pathetic excuse for a troll thats all it can ever manage.