[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.

[Michael Rasmussen]

On Wed, 24 Aug 2016 09:45:39 +0200
Michael Rasmussen <mir at datanom.net> wrote:

> I can test on infiniband when I get home today.
> 
mir at esx1:~$ time dd if=/tmp/big.file bs=32K |ssh esx2 "dd of=1GB.file bs=32k"32768+0 records in
32768+0 records out
1073741824 bytes (1.1 GB) copied, 3.75128 s, 286 MB/s
2632+60272 records in
2632+60272 records out
1073741824 bytes (1.1 GB) copied, 3.44421 s, 312 MB/s

real	0m3.760s
user	0m2.020s
sys	0m1.972s

mir at esx1:~$ time dd if=/tmp/big.file bs=64K |ssh esx2 "dd of=1GB.file bs=64k"
16384+0 records in
16384+0 records out
1073741824 bytes (1.1 GB) copied, 3.46228 s, 310 MB/s
289+62546 records in
289+62546 records out
1073741824 bytes (1.1 GB) copied, 3.33496 s, 322 MB/s

real	0m3.471s
user	0m1.984s
sys	0m2.016s

mir at esx1:~$ time dd if=/tmp/big.file bs=128K |ssh esx2 "dd of=1GB.file bs=128k"
8192+0 records in
8192+0 records out
1073741824 bytes (1.1 GB) copied, 4.19233 s, 256 MB/s
0+63726 records in
0+63726 records out
1073741824 bytes (1.1 GB) copied, 3.87772 s, 277 MB/s

real	0m4.198s
user	0m1.804s
sys	0m2.108s

Seems 64k is a good value.

-- 
Hilsen/Regards
Michael Rasmussen

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