Paul Gardner wrote:
>Hi all
>
>I have a knowledge gap in how the cluster works - reading the
>whitepaper, it implies (as do the other docs) that no changes are
>required to the application to support the cluster and it's failover
>capabilities.
>
>But the whitepaper also says that as well as storage nodes, which I
>understand executes all the transactions, you also need MySQL Server
>nodes in addition which is what the application connects to. The MySQL
>server nodes then transact with the storage node(s). If the Mysql
>server node fails, then surely the application does, after all, need to
>have failover logic built in, to push transactions to some other mysql
>server, as the application cannot talk directly to the storage nodes?
>Is this right? Surely not?
>
>
You are correct - if the MySQL server node (API node) fails, but you are
running multiple API nodes then your application must be able to handle
failing over to another API node. If a DB node fails, the cluster
handles that internally and, besides any current transactions being
aborted, shouldn't cause any problems with the API nodes or your client
applications.
>
>Another question - I understand the storage nodes require large RAM (db
>* 2) and large CPU - but how powerful do these mysql server nodes need
>to be in terms of ram/cpu?
>
>
This really depends on the size of the table you will be storing in the
NDB engine. For a small table that handles many transactions, a modern
desktop computer would even work, I believe. I have been testing on
2.8Ghz P4 Xeon's with ATA133 7200 rpm drives and 1G ram, and everything
seems to be fine. Albeit, I can not store a large table on such small
machines, they handle smaller tables just fine. By large table, I don't
mean lots of rows, I mean total size (num rows * (row size + index size
+ overhead) ).
Devananda
Neopets, Inc
