> >Just a silly question: are you pushing those 12.5 Mbytes/s over the
> >network ? If this is the case you have hit the limit of Fast Ethernet
> >(12.5x8 = 100Mbits/s) and no database (not even MySQL ;) ) will be
> >faster ! May be an upgrade to Gigabit Ethernet would help...
> yes, 12.5 MBytes/s over the network. We know this is the max of the
> network. We will be teaming the two nics on the box on Monday which will
> give us 25 Mbytes/s. That will eliminate one possible problem. However,
can
> MySQL (or MSSQL) push out 25 MBytes/s? (we will hit this limit in
February
> with the current setup). Can MySQL (or MSSQL) push out 125 MBytes/s (1
> GBit/s)? At what point do we reach the Application (or OS?) limit?
I think it is optimistic to expect even to get 12.5Mbyte/sec out of 100Mbit
Ethernet. Most people reckon that you can only get about 50% of theoretical
bandwidth. We have found that on a single stream we can get about 90% - but
this means configuring the ethernet for Jumbo Packets, which not many
people support. Without those, I really wouldn't expect to get more than
about 75-80% of theoretical throughput.
On your general question, given that you have said that the database can
conveniently cache in Ram, I would have thought that it mostly depend upon
your query structure and indexes. There will be a signoificant overhead in
parsing individual queries, so if you are doing queries which return one
hit, the parse time will be significant. On the other hand, if you are
doing queries which return many hits, using only an index for searching, I
would have thought a powerful CPU could fill a GBit link. Put in some JOINs
and ORDER BYs, and performance will inevitably fall.
Alec Cawley
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