Hi,
2005-02-02 kl. 01.58 skrev Mike Schroeder:
> I have similar questions:
>
> So if we use dual 64-bit AMD Opterons with 16 GB RAM, will MySQL
> access all 16 GB?
> Has anyone found any point of diminishing returns on the amount of
> memory in a server?
> Which is better: fewer servers with more memory, or more servers with
> less memory?
>
If the OS is 64-bit the answer is yes, both for the MySQL Server and
for the ndbd processes
in the MySQL Cluster. For a 32 bit OS, the limitation on OS exists as
Marco W. pointed out
below. For ndbd processes Marco W. notes were correct that you can run
several ndbd processes
per box to make use of a memory bigger than 4 GB (my experience is that
the limit is even 3 GB or
less since the OS uses up some of the virtual memory addresses plus due
to fragmentation of
virtual memory address space).
Whether to use fewer servers or more servers is more dependent on the
number of CPU's. One ndbd
can make use of between 1-2 CPU's so if you have a 4-CPU box you need
at least two ndbd or one
ndbd + mysqld to fully utilise the CPU's. It is also a matter of
whether best throughput or lowest latency
is desired. Best throughput is achieved if you allocate around 1 CPU
per ndbd node and best latency
if you have 1.5-2 CPU's allocated to the ndbd process. Actually in
multi-CPU boxes it can be very
beneficial to lock the ndbd process to a CPU (advantegous also from use
of cache memory and gives
very predictable performance) if the OS supports such actions.
Rgrds Mikael
>
>
>
>
> Marco Wertejuk wrote:
>
>> Hey,
>>
>> | What is the limitation of a 32-bit architecture as it
>> | relates to RAM and MySQL Cluster?
>>
>> I actually don't know about how mysql cluster is programmed
>> according to memory usage, but I can tell you that no
>> application can use more than 4GB memory on 32bit x86
>> servers. Redhat enterprise supports more that 4GB using
>> high address memory and em64t technology, but due to
>> how memory configurations above the 32bit address limitations
>> are supported no application can use more than 4GB.
>>
>> Of course you can run 2 4GB memory consuming applications
>> on you 8GB server but this might not work with mysql cluster.
>>
>> You should probably consider using a 4 node cluster where
>> you have 2 groups with each 2 nodes for redundancy and splitting the
>> dataset across two servers.
>>
>> I think this will be easier for you at the cost of
>> more hardware and probably more point of failures.
>>
>>
>
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>
Mikael Ronström, Senior Software Architect
MySQL AB, www.mysql.com
Jumpstart your cluster:
http://www.mysql.com/consulting/packaged/cluster.html
