[linux-lvm] bcache as a new i/o layer?

[Zdenek Kabelac]

Dne 30. 11. 18 v 10:35 Gionatan Danti napsal(a):
> Hi list,
> in BZ 1643651 I read:
> 
> "In 7.6 (and 8.0), lvm began using a new i/o layer (bcache)
> to read and write data blocks."
> 
> Last time I checked, bcache was a completely different caching layer, 
> unrelated from LVM. The above quote, instead, implies that bcache is now 
> actively used by LVM.
> 
> Am I missing something? Can you explain how they interact/behave?



Hi


The name of i/o layer bcache is only internal to lvm2 code for caching
reads form disks during disk processing - the name comes from usage
of  bTree and caching - thus the name bcache.

It's not a dm target - so nothing you could use for LVs.
And has nothing in common with exiting  bcache kernel block device.

The only purpose is to slightly accelerate device scanning and probing - and 
helps mostly in cases your system has tons a devices that needs to be scanned,
since this bcache is also using async disk reads for its filling....


Regards

Zdenek