[dm-devel] reply： Thinly-Provisioned Logical Volumes

[Zdenek Kabelac]

Dne 24.9.2014 v 04:11 lilofile napsal(a):
> When I test thinly-provisioned logical volumes,I use dd if=/dev/zero of=/dev/mapper/mythinvolume count=1 bs=4k
> I only write 4k data in mythinvolume.but In thin_map functions, I found there are really  4K data written,but I found more read IO,probably dozens of read io. who issue these IO?
>

Hi

I'd have guessed those I/O are likely metadata update related - at most every 
second metadata are synchronized to your metadata storage volume.
(Thin pool consists of _tdata data volume where provisioned chunks are located 
and _tmeta metadata volume).

And btw you could use tools like thin_dump  to explore how is your pool used,
which chunks belong to which volume, which are share and so on....

Regards

Zdenek