Re: [linux-lvm] LVM and HSM?

2019-05-13 Thread Gionatan Danti 

Il 13-05-2019 10:26 Zdenek Kabelac ha scritto:

Hi

There is no technical problem to enable caching of cached volume (aka
convert cache_cdata LV into another 'cached' volume.
And as long as there are not errors anywhere - it works.
Difficulty comes with solving error cases - and that's the main reason
it's not enable so far.
So I don't see big issue with enabling usage on 'user's own risk'.


Hi, how "cache of cached volume" is tiered/hierarchical storage?
In such a case, total available space is the sum of all storage 
hierarchy. For example, using 1 TB SSD + 8 TB HDD would result in 9 TB 
total in a tiered/hierarchical case, while "only" 8 TB on a cached 
setup.


Am I missing something here?

The interesting thing is that LVM already supports something similar to 
tiered storage, as pvmove can be used to migrate hot physical extent to 
faster devices. The hard/manual thing is to determine *which* extent to 
move/migrate.


Regards.

--
Danti Gionatan
Supporto Tecnico
Assyoma S.r.l. - www.assyoma.it
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Re: [linux-lvm] LVM and HSM?

2019-05-13 Thread Zdenek Kabelac 

Dne 12. 05. 19 v 0:07 Roy Sigurd Karlsbakk napsal(a):

Hi

With lvmcache and all, is there anything in the works of making an HSM 
(Hierarchical storage management aka tiered storage) with LVM as with less-used 
data on slow, spinning rust and more-used data on higher tiers?



Hi

There is no technical problem to enable caching of cached volume (aka  convert 
cache_cdata LV into another 'cached' volume.

And as long as there are not errors anywhere - it works.
Difficulty comes with solving error cases - and that's the main reason it's 
not enable so far.

So I don't see big issue with enabling usage on 'user's own risk'.


Regards

Zdenek

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