erasure pool with isa plugin

erasure pool with isa plugin

[Deneau, Tom]

If one has a cluster with some nodes that can run with the ISA plugin
and some that cannot, is there a way to define a pool such that the
ISA-capable nodes can use the ISA plugin and the others can use say
the jerasure plugin?

-- Tom Deneau

--
To unsubscribe from this list: send the line "unsubscribe ceph-devel" in

Re: erasure pool with isa plugin

[Loic Dachary]

[-- Attachment #1: Type: text/plain, Size: 595 bytes --]

Hi Tom,

On 22/06/2015 17:10, Deneau, Tom wrote:
> If one has a cluster with some nodes that can run with the ISA plugin
> and some that cannot, is there a way to define a pool such that the
> ISA-capable nodes can use the ISA plugin and the others can use say
> the jerasure plugin?

There is no way to do that, because there is no guarantee that an object encoded by jerasure can be decoded by isa and vice versa.

Cheers

> 
> -- Tom Deneau
> 
> --
> To unsubscribe from this list: send the line "unsubscribe ceph-devel" in
> 

-- 
Loïc Dachary, Artisan Logiciel Libre


[-- Attachment #2: OpenPGP digital signature --]
[-- Type: application/pgp-signature, Size: 198 bytes --]

Re: erasure pool with isa plugin

[Gregory Farnum]

On Mon, Jun 22, 2015 at 10:34 PM, Loic Dachary <loic@dachary.org> wrote:
> Hi Tom,
>
> On 22/06/2015 17:10, Deneau, Tom wrote:
>> If one has a cluster with some nodes that can run with the ISA plugin
>> and some that cannot, is there a way to define a pool such that the
>> ISA-capable nodes can use the ISA plugin and the others can use say
>> the jerasure plugin?
>
> There is no way to do that, because there is no guarantee that an object encoded by jerasure can be decoded by isa and vice versa.

Shouldn't we be able to set up something that *does* guarantee that,
though? Either by combining them into a single plugin which
dynamically configures to the fastest possible for that machine, or by
running them against the same object corpus and requiring that they
produce the same output?
-Greg

Re: erasure pool with isa plugin

[Loic Dachary]

[-- Attachment #1: Type: text/plain, Size: 1174 bytes --]

Hi,

On 23/06/2015 06:06, Gregory Farnum wrote:
> On Mon, Jun 22, 2015 at 10:34 PM, Loic Dachary <loic@dachary.org> wrote:
>> Hi Tom,
>>
>> On 22/06/2015 17:10, Deneau, Tom wrote:
>>> If one has a cluster with some nodes that can run with the ISA plugin
>>> and some that cannot, is there a way to define a pool such that the
>>> ISA-capable nodes can use the ISA plugin and the others can use say
>>> the jerasure plugin?
>>
>> There is no way to do that, because there is no guarantee that an object encoded by jerasure can be decoded by isa and vice versa.
> 
> Shouldn't we be able to set up something that *does* guarantee that,
> though? Either by combining them into a single plugin which
> dynamically configures to the fastest possible for that machine, or by
> running them against the same object corpus and requiring that they
> produce the same output?

I don't know enough about the maths involved to evaluate how difficult it is. Although both implement Reed Solomon using Vandermonde or Cauchy matrices, I think there are details that makes the output different. 

Cheers

> -Greg
> 

-- 
Loïc Dachary, Artisan Logiciel Libre


[-- Attachment #2: OpenPGP digital signature --]
[-- Type: application/pgp-signature, Size: 198 bytes --]