[OpenAFS] Getting started with OpenAFS

Lars Schimmer l.schimmer@cgv.tugraz.at
Fri, 30 Apr 2010 14:42:30 +0200

Hash: SHA1

Mike Pliskin wrote:
> Dear Lars,

(please, TOFU)

> Thanks a lot for the detailed response, let me see what I can do in ter=
ms of partitions. Generally the task I am trying to solve is the followin=
>  - there is a 100-gigabyte collection of large files (10 mb to 1 gb)

No problem, we have >5 TB of data in OpenAFS which includes files of
20GB so far. But for files >4GB you need at least a client version >1.4.0.

>  - there are several geographically distributed sites with people that =
need access

Readonly access or read/write access the same data or different
directories? Thats a important point as only one read/write copy of a
volume/directory can exist in one OpenAFS cell.

>  - files are organized in folders, and there is a fairly good administr=
ative separation on who needs which files - i.e. chances of people writin=
g the same file at once are pretty low

You can set ACLs on directories in OpenAFS - fairly simple and works.

>  - speed is important as well as a way to access any file from anywhere=
 (but ok to degrade speed if replicas aren't synced yet)

Readonly replica could be done via night and clients can access a local
readonly replica for faster access (if a local fileserver exists).
The client cache could do a difference, to. Needs to be big enough (for
bigger files) and persistant over reboots. If a file could be served out
of client local cache and not from (slow) server overseas fine.

> So the question is - do you think OpenAFS is a right tool for this prob=

So far yes. BUT the read/write and readonly point is still open.
You could setup one volume per directory and mount that directories
after the rules of rw access into the filetree.
But if you have e.g. a /afs/test/useraa/files/ firectory for user aa on
a fileserver in dk and a user bb in the US needs to write to that
directory, it needs to access that fileserver the rw volume is on.
If user bb in the us need only to access a readonly copy of that
directory, copy that volume/directory to the us fileserver (over night)
and the user bb could access it readonly from the us local fileserver.

Hope it is made clear now why it needs some think-over with a
multi-homing site. But it is absolute possible and could work great.

> Thanks,
>   Mike

Lars Schimmer
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