Re: Ceph for online file storage

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Hello,

firstly, wall of text, makes things incredibly hard to read.
Use paragraphs/returns liberally.

Secondly, what Yang wrote.

More inline.
On Sun, 26 Jun 2016 18:30:35 +0000 (GMT+00:00) m.danai@xxxxxxxxxx wrote:

> Hi all,
> After a quick review of the mailing list archive, I have a question that
> is left unanswered: 

Is that your entire experience with Ceph, ML archives and docs?

>Is Ceph suitable for online file storage, and if
> yes, shall I use RGW/librados or CephFS ? 

What's an "online storage"? 
I assume you're talking about what is is commonly referred as "cloud
storage".
Which also typically tends to use HTTP, S3 and thus RGW would be the
classic fit. 

But that's up to you really.

For example OwnCloud (and thus NextCloud) can use Ceph RGW as a storage
backend. 

>The typical workload here is
> mostly small files 50kB-10MB and some bigger ones 100MB+ up to 4TB max
> (roughly 70/30 split). 
10MB is not a small file in my book, 1-4KB (your typical mail) are small
files.
How much data (volume/space) are you looking at initially and within a
year of deployment?

What usage patterns are you looking at, expecting?

>Caching with SSDs is critical in achieving
> scalable performance as OSD hosts increase (and files as well). 

That's quite the blanket statement and sounds like from A sales brochure. 
SSDs for OSD journals are always a good idea.
Ceph scales first and foremost by adding more storage nodes and OSDs.

SSD based cache-tiers (quite a different beast to journals) can help, but
that's highly dependent on your usage patterns as well as correct sizing
and configuration of the cache pool.

For example one of your 4TB files above could potentially wreck havoc with
a cache pool of similar size.

>OSD
> nodes have between 12 and 48 8TB drives. 

Are we talking about existing HW or what you're planning?
12 OSDs per node are a good start and what I aim for usually, 24 are
feasible if you have some idea what you're doing.
More than 24 OSDs per node requires quite the insight and significant
investments in CPU and RAM. Tons of threads about this here.

Read the current thread "Dramatic performance drop at certain number of
objects in pool" for example.

Also, avoid large variations in your storage nodes if anyhow possible,
especially in your OSD sizes.

Christian

>If using CephFS, the hierarchy
> would include alphabet letters at the root and then a user's directory
> in the appropriate subfolder folder. With native calls, I'm not quite
> sure on how to retrieve file A from user A and not user B. Note that the
> software which processes user data is written in Java and deployed on
> multiple client-facing servers, so rados integration should be easy.
> Kind regards, Moïn Danai.


-- 
Christian Balzer        Network/Systems Engineer                
chibi@xxxxxxx   	Global OnLine Japan/Rakuten Communications
http://www.gol.com/
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