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Re: question about modern lamp clustering technique [long]

2010/10/21 Valentine Gostev <core.longbow@gmail.com>:
> Hello,
> from my point of view load balancing and failover capabilities should
> be provided on application level, not OS level.

>From my point it looks the same, but it's typical sittuation that we
have software installed.

> In this particular case, when you are having 2 rather strong servers
> and using virtualization solution I would suggest the following:
> Let's look at load of every role you use:
> mysql and postgres besides CPU and RAM consume good amount of disk
> I/O, that's why the VMs with
> mysql and postgres should be located on different hardware nodes to
> distribute disk system load.

Generally vast of servers that I work with have mysql cache hit rate
about 80-90% so there's no big I/O utilization.
Resources partitioning on xen server is very simple and reliable -
generally VMs have almost direct access to hardware so having 3 or 4
DomU's on such machine is similar to having 3/4 physical 1Us (not
talking about cos-effectiveness)

> And from my young experience I could say that DB clustering is a
> rather complicated way and it may also
> make some limitations, so, IMHO, the best way is to modify an
> application a bit and place different tables
> from DB at different DB servers and use them simultaneously.

Yup, clustering mysql is EVIL and this is yet the very part that you
have to code your software so it will have loadbalancing hardcoded.

> Hope that my thoughts will help a bit in choosing a proper solution.

Sure, thanks ;)

Wojciech Ziniewicz

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