[linux-lvm] Reserve space for specific thin logical volumes

[Gionatan Danti]

On 12/09/2017 16:37, Zdenek Kabelac wrote:
> ZFS with zpolls with thin with thinpools running directly on top of device.
> 
> If zpools - are 'equally' fast as thins  - and gives you better protection,
> and more sane logic the why is still anyone using thins???
> 
> I'd really love to see some benchmarks....
> 
> Of course if you slow down speed of thin-pool and add way more 
> synchronization points and consume 10x more memory :) you can get better 
> behavior in those exceptional cases which are only hit by unexperienced 
> users who tends to intentionally use thin-pools in incorrect way.....

Having benchmarked them, I can reply :)

ZFS/ZVOLs surely are slower than thinp, full stop.
However, they are not *massively* slower.

To tell the truth, what somewhat slow me on ZFS adoption is its low 
integration in the Linux kernel subsystem. For example:
- cache duplication (ARC + pagecache)
- slow reclaim of memory used for caching
- SPL (sun porting layer)
- dependency on 3rd part module
...

Thinp is great tech - and I am already using it. I did not started this 
thread as ZFS vs Thinp, really. Rather, I would like to understand how 
to better use thinp, and I traced a parallelism with ZVOLs, nothing more.

Thanks.

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Danti Gionatan
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