[Users] ploop block size

[Kir Kolyshkin]

On 04/15/2016 06:11 PM, Nick Knutov wrote:
> I think I saw it in the wiki but was unable to find now
>
> How to create ploop CT with vzctl create using smaller ploop block 
> size then defaut 1MB ? Can I change it in some config file?
>

This functionality is not available from vzctl, but if you create ploop 
using "ploop init"
you can use -b argument to specify ploop block size. Here's an excerpt 
from ploop(8)
man page:

    Basic commands

    init

        Create  and  initalize  a  ploop image file and a corresponding 
DiskDe‐
        scriptor.xml file.

        ploop init -s size [-f format] [-v version] [-t fstype] [-b 
blocksize]
                   [-B fsblocksize] [--nolazy] delta_file

....

        -b blocksize
                   Device block size, in 512 byte sectors. Default 
block  size
                   is 2048 sectors, or 1 megabyte.

....

So, you can experiment with various block sizes and share your findings 
with us.
I played with it a bit, but I was mostly interested in metadata overhead 
for small
(read empty) deltas, and found out that the block size of 512KB is a bit 
better
in that regard than the default 1M block size. Having said that, I 
haven't done
any performance comparisons -- obviously, block size should have noticeable
performance impact.

Kir.