Multiple trackers on a Mysql multi-master setup

Mark Smith smitty at
Thu Jan 31 18:52:46 UTC 2008

>  I'm wondering how to perform the setup of a second tracker. Do I start the
> second tracker the same as the first tracker, or do I need to do some
> configuration on both trackers so that they know about eachother?

The trackers don't need to know about eachother, they're happy
existing in their own little world.  The only thing you will want to
watch is the fsck job, IIRC you should only run one of those across
the cluster.  (I don't think it breaks anything to run it from two
locations, it's just not efficient/extra load.)

>  Also, I want to set this up in a mysql multimaster situation, probably
> having each tracker talk to the mysql instance on the machine it's on. From
> what I know about mogile, that shouldn't be a problem. Is there anything I
> should know about setting mogile up in this way?

Actually, I don't think MogileFS supports multiple masters in that
way.  Not by default anyway, since it uses the MySQL AUTO_INCREMENT
type, which isn't going to work in a master-master setup if you're
writing to both.  (Key collisions.)

However, you can get around this by assigning FIDs manually when you
insert files.  You'd need a separate key generation application and
perhaps use something like 64 bit numbers to reduce the collisions.
That would allow you to do the kind of setup you're talking about.

I've not personally spent any time testing MogileFS in a master-master
configuration, but I can't see why it shouldn't work.  YMMV, let us
know if you do any testing.  Of course the kind of problems you'd
expect won't really show up in lightly loaded conditions...

Mark Smith / xb95
smitty at

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