Re: I'm confused...

[Alexander Keremidarski]

Hi,

arne wrote:

> I have 6 machines and want to set them up as a
> cluster. On each machine should be a local MySQL
> instance running, so that the client on each
> machine can connect to 'localhost'.

Keep in mind that each of these MySQL servers can appear as SQL Node in your cluster.

You can have separate 1..N Data nodes (NDBD) running on same or separate machines (the latter is obviously better for both redundancy and load balancing)

> Now, as I understand, each NDBD will have a
> fragment of the database... so if I have 6 NDBDs
> (one on each machine), will this also be
> redundant? So, if one machine goes down, the
> others can still work? Or do I need to configure
> replicas to get redundancy? If yes, how many would
> be necessary/a good value?

6 nodes and 2 data replicas each NDBD wll store 2/6 of the data.

The data will be partitioned into 6 partitions. Two copies of each partition will be spread across 6 NDBD in a way that each NDBD stores two different partitions.

If you draw it in a diagram with boxes you will see why you can lose half of the NDBD and the rest can still work.

> The machines are each equipped with 1 GB RAM, but
> will also run apache and the client programs,
> doing some MRTG like stuff.

I would prefer to set some of your 6 machines as NDBD dedicated and the rest as MySQL+Apache+MRTG machines, but that's indeed subject of separate discussion.

Say 4 NDBD machines and 2 MySQL + Apache + MRTG