memcached "backends" (was Re: Simple questions from memcachednewbie)

Jeetendra Mirchandani jeetum at
Thu Oct 12 20:58:34 UTC 2006

Hey Andy,
Let me try to explain a scene.

Say, the cache is all I can serve out to a user. Processing data taks
just too much time.
In case I see a cache miss, I dont serve out anything, but
asynchoronously bring the data into cache, so that next time the user
comes back, he should get the results.

In such a scene, losing a memcached instance means losing data, a lot
of it! Hence I would want to back up the data to mysql or bdb or a
similar persistent store.

There could be more use cases. I have encountered quite a few problems
that have this type of requirement!


On 10/12/06, Andrew Harbick <aharbick at> wrote:
> I've been watching this thread and I don't quite understand the interest
> in having a different "backend" for memcache.  I'm using it as a caching
> layer (as I expect most people are) between my application and database.
>   In my case there is no reason to use a different "backend" other than
> memory.  I'm just curious about your applications.
> Andy
> Randy Wigginton wrote:
> > I've customized MemCached with a (local) mysql backend.  It works for
> > our purposes, but is not a general approach.
> >
> > I found that BDB was surprisingly slow.  MySQL runs in its own thread,
> > which gives it a nice processing advantage.
> >
> > The idea of a "pluggable" backend is positively brilliant.  Should
> > probably be a part of the next release.
> >
> > On Oct 12, 2006, at 1:51 AM, Marcus Bointon wrote:
> >
> >> On 12 Oct 2006, at 06:29, Jeetendra Mirchandani wrote:
> >>
> >>> Tugela actually replaces the in-memory store with BDB
> >>> Ideally i would just want a transactional BDB as a backing store, and
> >>> still have the usual memcached
> >>
> >> Wouldn't sharedance ( achieve much the
> >> same thing? Though it's not related to memcache, it effectively does
> >> the same thing, but replaces the in-memory store with regular file
> >> storage. The only thing I'd like on sharedance would be its own RAM
> >> cache over the top of its file-based storage. The author suggests
> >> storing it on a RAM-based file system, but that loses you the main
> >> advantages of sharedance (unlimited capacity, better persistence) -
> >> you may as well be using memcache.
> >>
> >> All these things seem so similar, it's a wonder that we don't see a
> >> hybrid solution with pluggable back-ends.
> >>
> >> Marcus
> >> --Marcus Bointon
> >> Synchromedia Limited: Creators of
> >> marcus at |
> >>
> >>
> >


"Reality is merely an illusion, albeit a very persistent one."

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