I read the Google blog post regarding these patches. They admit using
MySQL for some internal data storage needs but not in the general search
system. Here is the link to the blog post
----- Original Message -----
From: "David T. Ashley" <dashley@stripped>
Sent: April 25, 2007 10:20 PM
Subject: Re: FW: MySQL patches from Google
> On 4/25/07, mos <mos99@stripped> wrote:
> > At 02:36 PM 4/25/2007, you wrote:
> > >On 4/25/07, Daevid Vincent <daevid@stripped> wrote:
> > >>
> > >>A co-worker sent this to me, thought I'd pass it along here. We do
> > of
> > >>failover/replication and would be eager to see mySQL implment the
> > >>patches in the stock distribution. If anyone needs mission critical,
> > >>scaleable, and failover clusters, it's Google -- so I have every
> > >>confidence
> > >>their patches are solid and worthy of inclusion...
> > >
> > >
> > >This isn't surprising for Google. They've done the same thing to
> > >
> > >I don't know much about Google's infrastructure these days, but several
> > >years ago they had a server farm of about 2,000 identical x86 Linux
> > machines
> > >serving out search requests. Each machine had a local hard disk
> > containing
> > >the most recent copy of the search database.
> > So you're saying they had a MySQL database on the same machine as the
> > webserver? Or maybe 1 webserver machine and one MySQL machine?
> > I would have thought a single MySQL database could handle the requests
> > from
> > 25-50 webservers easily. Trying to maintain 2000 copies of the same
> > database requires a lot of disk writes. I know Google today is rumored
> > have over 100,000 web servers and it would be impossible to have that
> > databases in sync at all times.
> When I read the article some years ago, I got the impression that it was a
> custom database solution (i.e. nothing to do with MySQL).
> If you think about it, for a read-only database where the design was known
> in advance, nearly anybody on this list could write a database solution in
> 'C' that would outperform MySQL (generality always has a cost).
> Additionally, if you think about it, if you have some time to crunch on
> data and the data set doesn't change until the next data set is released,
> you can probably optimize it in ways that are unavailable to MySQL because
> of the high INSERT cost. There might even be enough time to tune a hash
> function that won't collide much on the data set involved so that the
> cost becomes O(1) rather than O(log N). You can't do that in real time on
> an INSERT. It may take days to crunch data in that way.
> My understanding was the Google's search servers had custom software
> operating on a custom database format. My understanding was also that
> each search server had a full copy of the database (i.e. no additional
> network traffic involved in providing search results).
> As far as keeping 100,000 servers in sync, my guess would be that most of
> the data is distilled for search by other machines and then it is rolled
> automatically in a way to keep just a small fraction of the search servers
> offline at any one time.
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