[ale] Copy-on-write file?

[Greg Freemyer]

On Mon, Jan 18, 2010 at 11:03 AM, JK <jknapka at kneuro.net> wrote:
> On 1/18/2010 6:37 AM, Greg Freemyer wrote:
>> Another option is getting that 80GB copy down to 20 minutes.
>>
>> Is that fast enough?
>
>
> Yes, that would be fast enough.
>
>
>> If so, just put the 80GB image on a different physical disk than where
>> you want to restore it.  That eliminates all the disks seeks you must
>> currently have.
>
>
> They're on separate physical disks already.  But old ones :-/
>
>
>> 4GB/min is very doable with a 64bit kernel/cpu and sata drives.
>
> I have a suitable machine, but I'd need to pick up a couple more
> SATA drives, which is probably overkill for this task.  The machine
> I'm doing the recovery on has only PATA interfaces, and the drives
> are only capable of UDMA33.
>

That is slow, but it still should not take 5 hours.

One more question, how did you do the copy.

I use dd a lot for this type of thing and it defaults to just a 512
byte i/o block size.  Highly inefficient when talking to a filesystem.
 Using 4K blocks can greatly speed it up.

ie. dd bs=4K if=... of=...

Greg