[pve-devel] [PATCH] Increases the dd read/write speed when migrating LVM disks. This should bring LVM migration speed up to match that of rsyncing qcows.

[James Lavoy]

Totally up to you guys. Anything higher than default is a marked
improvement.

I got similar speed results doing the same test with 1M.

abrams Code # time dd if=1GB.file bs=1M |ssh mary "dd of=/root/1GB.file
bs=1M"
1024+0 records in
1024+0 records out
1073741824 bytes (1.1 GB) copied, 10.002 s, 107 MB/s
0+65478 records in
0+65478 records out
1073741824 bytes (1.1 GB) copied, 9.88115 s, 109 MB/s

real    0m10.005s
user    0m7.454s
sys     0m2.610s


On Tue, Aug 23, 2016 at 3:26 AM, Dietmar Maurer <dietmar at proxmox.com> wrote:

> > +                 run_command([["dd", "if=$src",
> "bs=64M"],["/usr/bin/ssh",
> > "root\@${target_host}",
> > +                           "dd", 'conv=sparse', "of=$dst", "bs=64M"]]);
>
> IMHO a block size of 64MB is a bit too large. I guess you can see the same
> speed improvements with much smaller sizes - mabe 1M is large enough?
>
>