Re: [Xen-users] lvm size

[David Cundiff <dcundiff@xxxxxxxxx>]

Are you increasing the block size when you copy with dd??? Or are you 
just using the default which I believe is 512 bytes. I use dd to create 
my lvm's from template files. My template OS's are around 500M to 1G. 
For example.
inuyasha:~# time dd if=debian3.1 of=/dev/vds/lvol2 bs=1M
512+0 records in
512+0 records out
536870912 bytes transferred in 25.429652 seconds (21112004 bytes/sec)

real    0m25.432s
user    0m0.000s
sys     0m2.090s

25 seconds to copy a 500 meg file to the lvm and as you can see almost 
no cpu time was used. However if I don't increase the blocksize I get this.
inuyasha:~# time dd if=debian3.1 of=/dev/vds/lvol2
1048576+0 records in
1048576+0 records out
536870912 bytes transferred in 153.342399 seconds (3501125 bytes/sec)

real    2m33.345s
user    0m0.650s
sys     0m3.530s

Big difference huh?? 25 seconds to 2.5 minutes. Still doesn't thrash the 
processor but this is a dual 2.4ghz xeon with an ultra 160 scsi array.
Dave

Anand wrote:

> If i have two volumes test7 and test8. What is most efficient way to 
> copy data from one to another ?
> I did tests using cat, rsync, dd, cpio and all of them seem to be 
> consuming almost all of my dom0 256MB ram and cpu load goes up to a 
> max 1.65 (athlon 2.6ghz, 1gb ram)
> Infact dd takes more time to copy the data, ofcourse the reason being 
> the way it operates and copies sector by sector. All other tools 
> averaged time at 4.5 mins, dd took 6+mins.
> The test7 volume is of 850MB and the test8 volume is of 1GB. The test7 
> volume is actually the template for the centos which is used for 
> various domains.
> Can anyone please share their experiences on what they use to copy 
> data most efficiently ?
> --
>
> regards,
>
> Anand
>
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