SD backup while disk is in use

[Ronin]

I needed to clone a 1.5 TB data drive with roughly 900 GB on it to a 2 TB drive, but needed to use it as the transfer was going quite slowly (started at around 30 MiB/s but dropped to 10).

Obviously, anything that was changed after it was copied would not be up-to-date, but it appears that the operation continued to completion. Thereafter I did a smart update to bring things up-to-date when I went out for a bit and am presently running off of the 2 TB drive without apparent difficulty.

A couple of questions came to mind about this.

This first is, why was a straight erase and copy running so slowly? (I have an external 2 bay SATA enclosure that the drives were in which runs off of a PCI/SATA controller in a FW 800 G4 (dual 1.42 GHz) with OS 10.5.8.

Any thoughts about whether there are drawback to doing things this way?

Thanks

[dnanian]

Lots of little files tend to copy slower than big files. It's hard to know what overall speed is going to be... I'd generally expect about 8-20MB/s or so, but less on a G4...