[OpenAFS] Is OpenAFS for me?

John Hascall john@iastate.edu
Tue, 07 Mar 2006 09:06:14 CST

> Sorry if this has been answered but after several days trying to narrow 
> down to a dristributed filesystem, I am still unsure what to pick. I 
> have narrowed it down to two: OpenAFS, and GFS.
> Here is what I need:
> 1) Automatic data replication to multiple computers each with a drive 
> dedicated to the OpenAFS volume. If one computer goes down, the data is 
> still available from another computer.

   AFS replicates ReadOnly copies of a ReadWrite volume.
   All writes must go to the ReadWrite copy, if that server
   is down data can be read still, but not changed.

>    1a)  I plan on having 10 to 15 computers exporting one 400-500GB 
> drive..How many drives/computers can I lose without jeopardizing the 
> OpenAFS volume?

   All but one.

>     2a) What happens to the OpenAFS system if I have to bring all the 
> computers down, one by one?


> 2) Expandable. Can I add another 400-500GB drive to a new computer and 
> add it to an existing OpenAFS volume?

   No.  Not without some sort of layer below AFS.  All AFS volumes
   live in an existing filesystem on the server.  If the server has
   the capability to grow a filesystem unbeknownst to AFS that
   might work (but I personally am not aware of any such thing).

> 3) Does OpenAFS need RAID for redundancy or is it taken care of at the 
> filesystem layer?

   Having multiple ReadOnly copies provides for some protection
   (you can even recreate the ReadWrite copy from one of them).
   On the other hand disks are cheap, belt and suspenders...

> 4) Is there a 2GB file limitation? (I have read conflicting reports)

   We have volumes well over 2GBs.