Thanks in advance. Couple of things that would be good to start (please excuse
my ignorance if these questions seem silly): - What does the ``evacuate''
process refer to in the code? Taking stuff that was buffered in memory and
writing it to disk?- How is the metadata organized for the on-disk data
structures? It is a hash table? B+ tree? Something else?- How much metadata is
kept in the memory concerning the disk structures? I see in the code a
Lookaside table, but am not clear what mapping is being stored there.- Is
there any recovery process to address inconsistency following an unclean (say
power outage) shutdown of the cache?- How is a CacheKey generated from the http
object key (e.g. host + url + vary headers + alternates)? Looking at the code,
it seems that: - Vol corresponds to a disk file or raw disk partition. -
Within Vol we have Dir which seem to be storing metadata about actual
datablocks? (There is mention how Dir nodes are allocated every 8k block)
These seem to be chained together to comprise the Document (for example
Document stored over a number of Dir blocks). Is this on track, or am I totally
off base? Thanks > Date: Fri, 21 Dec 2012 14:45:31 -0800
> Subject: Re: How disk storage is implemented
> From: jplev...@gmail.com
> To: dev@trafficserver.apache.org
>
> Unfortunately most of the docs were lost when the code was in storage
> before being revived at yahoo. However I can answer questions and try to
> do a writeup in my spare time.
> On Dec 21, 2012 11:19 AM, "Wei Bo" <binary.bo...@live.com> wrote:
>
> >
> >
> >
> >
> > Hi all, Is there a document/notes available describing how the Apache
> > Traffic Server disk storage part of the cache is implemented/data
> > structures/layout? I would like to understand how the disk cache would
> > behave under various extreme conditions (lots of little objects, big
> > objects) and it's been hard trying to understand the disk cache just by
> > reading the code. Something like
> > https://cwiki.apache.org/TS/ramcache.html... Thanks,Wei Bo
> >
