[OpenAFS] humungous disk caches

[Derek Atkins]

Gee, and just a couple years ago I thought a 1G cache was too big..
It used to be that even a 1G cache would take HOURS to create, let
alone anything bigger.  That was fixed, but there are other limits
to the caching, as you're seeing.

Honestly, I think you'll run into a bunch of other hashtable
limitations when you get that big.  I also think you'll find that the
cache (as it's currently implemented) works better if it's smaller.

How big are these files that you're dealing with?

-derek

Bryan Bayerdorffer <bryan.bayerdorffer@analog.com> writes:

> Derrick J Brashear wrote:
> >>How about ext3?  Does the journaling get in the way at all?  Is ext2 the only
> >>safe option?
> > ext3 is fine.
> > reiserfs will blow up now, or later.
> 
> Ok, ext3 it is.  So what's the practical upper limit on the size of the disk
> cache?  Switching to ext3 didn't affect the apparent 16GB limit, beyond which
> the first access to /afs will hang.  Nothing in the kernel log. I haven't yet
> straced, but I will if there isn't an easy answer to this.
> 
> Our apps are characterized by very large files that are read often and modified
> only rarely, so I'd like to see if a large disk cache (128GB) will improve
> performance.
> 
> -- 
>     .. ..-. ..- -.-. .- -. .-. . .- -.. - .... .. ... --. . - .- .-.. .. ..-. .
> Bryan Bayerdorffer       bryan@meatspace.net              bryan@spd.analog.com
>                       (Wit's End Computation Center)           (Analog Devices)
> 
> "Sing, O goddess, the anger of Achilles son of Peleus, that brought countless
> ills upon the Achaeans."  -- Homer
> 
> "Donuts---is there anything they can't do?"  -- Homer
> 
> 
> 
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-- 
       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