[OpenAFS] Definitive list of AFS Limits?

Horst Birthelmer horst@riback.net
Thu, 21 Jul 2005 10:00:03 +0200

On Jul 21, 2005, at 7:16 AM, Christopher Mason wrote:

> Hello.

> Minimum file size (overhead): FAQ says 1k file occupies 1k, but  
> doesn't address overhead.

That's minimal and heavily depends on you directory structure. But  
not noticeable at all.
I said depends on your structure since you have mount points, ACLs  
etc. to handle on the fileserver. I never heard anybody complain  
about that in the past. (whatever that now means to you ...)

> Maximum file size: 2GB???  (is this still true?)
> <https://lists.openafs.org/pipermail/openafs-info/2002-November/ 
> 007006.html>

The release fileservers do have this limit.
If you're compiling the fileservers yourselves you can switch the  
large file support on, but that's experimantal AFAIK.

> Maximum files in a directory:  The limit depends on the length of  
> the filenames; if they are all sufficiently short, the limit is  
> around 64K.

This one's correct. ;-)

> Maximum files in a volume:
> Maximum size of a volume: 4TB
> <https://lists.openafs.org/pipermail/openafs-info/2004-November/ 
> 015530.html>

This would be approximately accurate as well (AFAIK it's not exactly  
4TB but somewhere in that area, never cared about the accurate  
number, though :-) )

> Number of servers for a read/write volume: 1 (by design)


> Maximum number of servers for a read only volume:
> Maximum size of a partition:
> (OS limited? -- linux = 9TB?)
OS limited since the partition is on a file system on your fileserver.

> (Be aware that there needs to be a special
> compile-time option enabled to support blockdevices larger  
> 2TB.<https://lists.openafs.org/pipermail/openafs-info/2005-April/ 
> 017336.html>)

Can't comment on that since I never had such devices :-)

> Maximum cache size:
>> My experience is that you want your client cache to be at least as
>> large as the largest files you are using.  Performance on files that
>> won't fit entirely in the cache is terrible.
> ... Setting cache size is a bit of a black art.
> <https://lists.openafs.org/pipermail/openafs-info/2005-April/ 
> 017552.html>

Yes, cache size and parameters for the clients is more like a  
religion :-)

> Total size of largest known AFS installation:
Now here i think you won't get any "proud and cocky" answer since the  
AFS guys are not running around with the number of TBs around their  
neck for every body to know. :-)
BTW, if you're using AFS it's the same way of handling data whether  
you handle 2.1GB or 200TB.

> Can an AFS volume be grown in size?  Shrunk in size?  While online?
They do that all by themselves since a volume is not a "physical  
unit" but an administrative one.