[OpenAFS-devel] suggested feature...

[Derek Atkins]

It _is_ possible for the cache size to be exceeded in certain cases,
IIRC.  I don't remember when, exactly.  For example, I think large
directories can certainly cause caches to get over-sized.

-derek

David Thompson <thomas@cs.wisc.edu> writes:

> Derek Atkins wrote:
> >David Thompson <thomas@cs.wisc.edu> writes:
> >
> >> This is a standard cache partition size:
> >> 
> >> Filesystem           1k-blocks      Used Available Use% Mounted on
> >> /dev/hda9               124427     89819     28184  77% /var/vice/cache
> 
> Sure:
> /dev/hda9           866       881    128488+  83  Linux
> 
> >Note that if you add up the 'used' and 'available' you get 118003,
> >which is an overhead (from the 124427) of about 5%.  However, I would
> >not want to put a 100M cache on a partition with only 110M of
> >available space.  In this case I would reduce the cache to ~95M, or
> >maybe even 90M.  Note that CacheItems appears to take approximately
> >4.4k per cachefile.  If you have a 100M cache, that's 100K files, or
> >an additional 4.4M of storage in the cache partition of the top.
> 
> Actually, we limit the number of cache slots to 10k for performance sake.  
> BTW, many thanks for the fix to allow more cache items without the massive dir 
> lookup overhead  :)  I look forward to using it.
> 
> root can create ~127 Meg of data on a partition of that size.  Mere mortals 
> can create ~120 Megs of data on that partition.  The file system overhead of 
> 10K empty files is very small (220k)
> 
> By your calculations, we should have 100Meg cache + .44M CacheItems overhead, 
> in a  118 Meg partition.  Also, since the cache manager is running as root, it 
> should be able to go into the 5% set-aside.  It still seems like the cache 
> size specified in the cacheinfo file is being exceeded (apparently by at least 
> ~17 Meg or ~17%).
> 
> Dave
> 

-- 
       Derek Atkins, SB '93 MIT EE, SM '95 MIT Media Laboratory
       Member, MIT Student Information Processing Board  (SIPB)
       URL: http://web.mit.edu/warlord/    PP-ASEL-IA     N1NWH
       warlord@MIT.EDU                        PGP key available