[clug] fastest way to copy a fs

Alex Satrapa grail at goldweb.com.au
Wed Jan 17 00:22:04 GMT 2007

On 17 Jan 2007, at 09:45, Eyal Lebedinsky wrote:

> I want to move a fs to a new disk, and considering what is the best
> way to do this.

Remember to put the source and destination disk on different  
controllers, whether you're using IDE, SATA, USB or FireWire. I'm not  
sure how "smart" SCSI is. Having the disks on different controllers  
means the bottleneck is halving the bandwidth of the PCI bus rather  
than halving the bandwidth of the drive controller. The catch with  
USB is figuring out whether you have one USB root hub with a bunch of  
ports sticking out the back of your computer, or you have an  
independent USB root hub controlling each port (or group of ports,  
such as front panel/back panel).

> I will then select the fastest one, which I can benchmark myself,  
> but are
> there important speedup options (I will run off a live DVD with the  
> source
> fs mounted ro).

Only a stab in the dark since I haven't tried this trick myself: but  
I wonder if it will help to mount the source andtarget file systems  
with the noatime option, since this should require one less read/ 
write of file system information for each file being copied.

I wonder if turning off the file system journal will help, since  
otherwise the file system will end up doing some of the work twice  
(writing stuff to the journal, then committing that stuff out to the  
file system). It just seems intuitive to me that the tradeoff of  
having disk writes completing faster in terms of latency (thanks to  
journalling) is that extra work is happening in the background, which  
will result in disk writes being slower in terms of throughput.


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