help a systems admin understand....

[William Ottley]

Hey there Kevin,

thanks for the information. I acutally had a great convo with
"dormando" over at #memcached on irc.
He was able to get me to understand the whole process. So now i've
basically installed memcached on the database and web servers. the
rest is up to the programmer :D

thanks!

On Dec 6, 2007 10:49 AM, Kevin Amerson <kevin.amerson at gmail.com> wrote:
> Memcached helps with reads, not writes to the database.  If someone is
> changing data, the operation steps would look like:
>
> 1. Update record in the master database
> 2. Invalidate or clear memcached key
> 3. Master database replicates out to slaves (hopefully at least one hot
> spare)
>
> So even though memcached is considered a layer on top of the database it
> really has nothing to do with the database.  Most web sites are read
> intensive and in those cases memcached can alleviate your database disk IO
> by doing the reads from memory instead of disk.  At least thats one way to
> look at it.
>
> You may be so successful at alleviating database load due to reads, that you
> can eliminate your replicated database servers as you mentioned below so
> that all writes can go to a single master database, thus simplifying your
> whole system.
>
> Kevin
>
>
>
> On Dec 3, 2007 1:06 PM, William Ottley <williamottley at gmail.com> wrote:
> > If memcached is just a layer of caching on top of the existing
> > database, can someone explain to me how its possible to have user #1
> > write to database #1, and have user #2 access database #2, with the
> > same "changed" information that user #1 wrote to database #1?
> >
> > if memcached is to communicate to all the databases, with the "server
> > list"? Is it that user #1 isn't really writing to the database, but
> > writing to the memcached? and then after a while it gets sent down to
> > the database? that's why user #2 can quickly access the writing done
> > by user #1, because all the memcached machines are fast, because its
> > all up in memory?
> >
> > Thanks for trying to get a systems admin to understand database
> > functionality! :$
> >
> > William
> >
> > On Dec 3, 2007 12:16 AM, Brian Moon <brianm at dealnews.com> wrote:
> > > William Ottley wrote:
> > > > hmm so really i should be bugging the people at livejournal, that use
> > > > memcached, to figure out how they are able to sync all of the "global"
> > > > servers they have that are using memcached....
> > >
> > > They sync their database servers, not their memcached.  Memcached is
> > > just a layer of caching on top of their database.
> > >
> > > PS. please respond on the list to get the most help possible.
> > >
> > > --
> > >
> > >
> > > Brian Moon
> > > Senior Developer
> > > ------------------------------
> > > http://dealnews.com/
> > > It's good to be cheap =)
> > >
> >
> >
> >
> > --
> > ---------------
> > Morpheus: After this, there is no turning back. You take the blue pill
> > - the story ends, you wake up in your bed and believe whatever you
> > want to believe. You take the red pill - you stay in Wonderland and I
> > show you how deep the rabbit-hole goes.
> >
>
>



-- 
---------------
Morpheus: After this, there is no turning back. You take the blue pill
- the story ends, you wake up in your bed and believe whatever you
want to believe. You take the red pill - you stay in Wonderland and I
show you how deep the rabbit-hole goes.