Replication ?

[Nathan Nobbe]

Hi all,

I know I'll get blasted for not googling enough, but I have a quick
question.

I was under the impression memcached servers replicated data, such that if i
have 2 servers and one machine goes down the data would all still be
available on the other machine.  this with the understanding that some data
may not yet have been replicated as replication isn't instantaneous.

Can you clarify for me?

thx,

-nathan

Re: Replication ?

[Nathan Nobbe]

On Thu, Mar 3, 2011 at 2:44 PM, Roberto Spadim wrote:

> more here:
> http://repcached.lab.klab.org/


This was the first thing that came up on google, just wanted to verify
memcached doesn't replicate out-of-the-box.

thx,

-nathan

Re: Replication ?

[Nathan Nobbe]

On Thu, Mar 3, 2011 at 3:02 PM, Roberto Spadim wrote:

> humm i will tell my experience
> there´s two ideas
> one replication (like raid1)
> other load balance (like raid0 stripe)
>
> client side can load balance like 'raid0' (i don´t know if libmemcache
> have this, in php i use it, and works well)
> repcache works like 'raid1' (for cluster and HA i´m using it without
> problems, and it´s very good!)
> memcachedb have non volatile tools (use harddisk/ssd 'cache' with a berkley
> db)
> there´s another memcache port but i don´t remember now, with more
> features (web administration and others tools)
>
> maybe in future we could put all in one package? i don´t know...


A friend has mentioned membase:

http://www.membase.org/

though I've hardly had a minute to investigate, it implements the memcache
protocol, but it sounds like it may use something other than libmemcache on
the backend.

-nathan

Re: Replication ?

[Nathan Nobbe]

On Thu, Mar 3, 2011 at 6:42 PM, dormando  wrote:

> > Hi all,
> > I know I'll get blasted for not googling enough, but I have a quick
> question.
> >
> > I was under the impression memcached servers replicated data, such that
> if i have 2 servers and one machine goes down the data would all still be
> > available on the other machine.  this with the understanding that some
> data may not yet have been replicated as replication isn't instantaneous.
> >
> > Can you clarify for me?
> >
> > thx,
> >
> > -nathan
>
> I sound like a broken record about this, but I like restating things
> nobody cares about;
>
> - memcached doesn't do replication by default
> - because not replicating your cache gives you 2x cache space
> - and when you have 10 memcached servers and one fails...
> - ... you get some 10% miss rate.
> - and may cache 2x more crap in the meantime.
>
> if your workload really requires cache data never disappear, you're
> looking more for a database (mysql, NoSQL, or otherwise).
>

hmm, i hear you here and am starting to wonder about the application of
memcached which drove me to this question, namely php session storage.

it's often discussed on the php-general list the pros and cons of memcached
in said application and i know many sites move to memcached to increase
performance over a db backend.  however there is the issue of loosing the
session if a memcached box goes down.  perhaps memcached isn't the most
appropriate place for session storage as its not considered data that should
be allowed to disappear.

i know its OT, but .. thoughts? :)

-nathan

Re: Linux Memcache distro

[Nathan Nobbe]

On Fri, Sep 26, 2008 at 7:46 AM, mlmoser <[EMAIL PROTECTED]> wrote:

>
> We use CentOS, a derivative of RedHat.  Your best bet for locating
> small Linux distros is
> http://distrowatch.com


there actually used to be a popular one called DamnSmallLinux.

i like systems like gentoo and debian (not derivatives) because the base
install has next to nothing aside from the package management software and a
very basic set of utilities.

-nathan

Re: DNS vs IP

[Nathan Nobbe]

On Wed, Oct 7, 2009 at 9:21 AM, Brian Moon  wrote:

>
> This has very little to do with memcached and everything to do with your
> DNS infrastructure.  The client that connects is what does the DNS
> resolution.  memcached has nothing to do with DNS.
>
> FWIW, we avoid dns lookups at all costs for memcached because it is just
> one more thing that has to happen before I can have my data.
>

also, fwiw, there are various ip-balancing solutions available for *nix.

for 2 boxes look at heartbeat / drbd  on linux.
 for more than that checkout LVS 

-nathan