[OpenAFS] /var/cache/openafs on btrfs

Dale Pontius pontius@btv.ibm.com
Thu, 5 May 2016 07:55:49 -0400

On 03/02/2016 01:54 AM, Fred Drueck wrote:
> Hello Everyone,
> According to the OpenAFS admin FAQ, it appears that the officially 
> supported file systems for the disk cache are:
> ext2
> ext3
> hfs (HP-UX)
> xfs (at least on IRIX 6.5)
> ufs (Solaris, ?Tru64Unix)
> which is clearly out of date, since there is a working implementation 
> for OS X that runs on top of HFS+
> For some time I've been fearlessly using both ext4 and btrfs (on 
> Linux, as you might infer) as the backing storage for my AFS client cache.
> I have noticed some fairly rare issues with the clients if all file/db 
> servers (in our cell the same machines) become unavailable.  The 
> '/afs' mount becomes un-accessible and attempts to access files often 
> result in very long timeouts. I've always been able to fix things by 
> somehow shutting down the client (in the worst case by physical 
> power-off and reboot into single user mode) and deleting the cache.
> Is there some chance that this is because I've been causing these 
> problems by using un-supported file-systems as the backing storage for 
> the client cache?
> I'm using fairly recent versions of the client, namely the version 
> packaged for debian-squeeze, debian-wheezy, ubuntu 14.04, and a very 
> recent release on Arch Linux.
> e.g.
> 1.6.9-2+deb8u4~bpo70+1
> Version:
> Version: 1.6.7-1ubuntu1.
> openafs
> For the most part, though, I haven't had many issues.  Does anyone 
> know any updated info on what the supported client filesystems are?
> Thanks!
> -Fred
I've been using an ext4 partition for my cache for years now.  There are 
several additional optimizations that can be done, but the only one I 
remember at the moment is to create the filesystem without a journal.  
Because ext4 natively allocates extents, these can directly map to cache 

I've been happy.

Dale Pontius

Dale Pontius
Senior Engineer
IBM Corporation
Phone: (802) 769-6850
Tie-Line: 446-6850
email: pontius@us.ibm.com

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