Retrospect backup speed

[geoff_green]

Hello. I've noticed that Retrospect is much much faster backing up to

 

ATAPI/IDE or SCSI devices than Firewire devices, and I wonder if anyone

 

can help explain that. I'm using Retrospect 5.0 for OS X, but I noticed

 

similar behavior using Retrospect 4.3 for OS9. (Note that these test results were obtained using Retrospect 5.0 Preview for OS X, but since the same thing happened under Retrospect 4.3, I don't expect any difference.)

 

 

 

I've got a Power Mac G4/867 with a built-in 12x CD-RW. However, before

 

I purchased this computer I had already acquired a QPS Que! 16x Firewire

 

CD-RW.

 

 

 

When I've backed up using the internal CD-RW drive onto CD-R discs I get

 

the following results:

 

 

 

Performance: 68.6 MB/minute (42.4 copy, 179.4 compare)

 

Performance: 62.6 MB/minute (40.6 copy, 136.0 compare)

 

 

 

However, when I've backed up using the Firewire CD-RW, using the same

 

backup set, it takes much longer:

 

 

 

Performance: 25.2 MB/minute (17.3 copy, 46.2 compare)

 

Performance: 25.0 MB/minute (17.2 copy, 45.6 compare)

 

 

 

I get similar performance numbers backing up to the Firewire using

 

Retrospect 4.3 for OS9.

 

 

 

Now, I once used a friends 4X SCSI CD-RW to backup my hard drive, using

 

Retrospect 4.3 for OS9, and the speed using that device was closer to

 

the results I get with the internal CD-RW than with the Firewire CD-RW.

 

 

 

My question is obvious: why is Retrospect so much faster backing up to

 

my internal CD-RW or to a SCSI CD-RW than to my Firewire CD-RW?

 

 

 

Thanks.

[IrenaS]

Retrospect loads it's own drivers to write to any supported CD-R drive. These drivers are written to work as efficiently and reliably as possible with the drive. There is no way to adjust the write speed, short of turning compression on or off.

 

 

 

Note that Retrospect writes in packet mode and will write data at the highest speed possible for your device. In some cases the firmware of a device will prevent Retrospect from writing data (in packet mode) at the normal designated write speed. This is true for the Panasonic CW-7503, Panasonic CW-7586, QPS Que! Fire 16x10x40 (TEAC) and a few other drives. Ultimately, we are limited by the drives ability to write effectively in packet-writing mode.

 

 

 

Not all FireWire drives are slow in packet-writing mode. I've seen speeds of up to 120 MB/min with a QPS Que! Fire 12x10x32x, among others. (No particular plug for this drive here; just an example.)

[geoff_green]

IrenaS:

 

 

 

Thanks for the response. I didn't know that. The external Firewire drive I have is the QPS! Que Fire 16x10x40, so that explains the slow performance.

 

 

 

Perhaps this is something that should be written up in some FAQ? I purchased the QPS drive because it was listed as being compatible with Retrospect, without any caveats, but if I knew about this severe speed penalty I'd have purchased some other Firewire CD-RW.

 

 

 

- geoff