Re: Does anyone know why cephfs do not support EC pool?

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On Tue, Oct 18, 2016 at 3:46 AM, Lars Marowsky-Bree <lmb@xxxxxxxx> wrote:
On 2016-10-18T00:06:57, Erick Perez - Quadrian Enterprises <eperez@xxxxxxxxxxxxxxx> wrote:

> Is EC in the roadmap for CEPH? Cant seem to find it. My question is because
> "all others" (Nutanix, Hypergrid) do EC storage for VMs as the default way
> of storage. It seems EC in ceph (as of Sept 2016) is considered by many
> "experimental" unless is used for cold data.

Right now (Jewel) you have to "cheat" and put a cache tier in front of
an EC pool if you want to use it for block or direct data access (like
CephFS). That actually works quite well, and you can then also use
much faster storage media in front of your dense EC pool.

The downside is you have to understand how to set some of the cache
tiering tunables and be able to size it appropriately, and understand
the impact of cache tiering on your cluster performance (e.g., the
overhead of the additional traffic between the tiers). Yet, it works
well.

Partial overwrites for EC pools directly is on the roadmap for
Kraken/Luminous, probably leveraging some of BlueStore's new features.
If I understood Sage correctly, he considers that a release criteria for
Luminous.

That'd allow us to directly access EC pools w/o the need for cache
tiering.



Regards,
    Lars

--
SUSE Linux GmbH, GF: Felix Imendörffer, Jane Smithard, Graham Norton, HRB 21284 (AG Nürnberg)
"Experience is the name everyone gives to their mistakes." -- Oscar Wilde

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Thanks Lars, I was reading about bluestore last night. I will wait for a Kraken release to test as much EC functionality as possible at least from a non-programmer point of use. Point and click tunables for EC is something that will for sure be needed at least for some of us that do not run a gazillion VMs and Petas of object storage.

Hopefully if i develop more know-how in EC I can help with testing predefined tunables that can be available for smaller installations to use, like the ones i use (always in Hewlett packard hardware)  at least in my country we do not run white-box hardware outside a lab.
I guess my first goal will be to learn how to obtain proper meaningful metrics when testing VM loads and object loads.


Thanks to all for the comments,

--

---------------------
Erick Perez 

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