CPU versus Memory

[adhillon]

I have read (in this forum) about people using dual quad-core servers with tons of RAM.

For Open-e, what provides a better return: CPU or RAM?
Is there an optimum level, after which there is no appreciable gain?

[derkgort]

Hi

I'm the guy who had loads of memory en dual quad 5335.
After a few weeks of testing my findings about this are that open-e or the iscsi target that is used (iscsitarget)

does not use more than one CPU
and when using blockio memory is not used because filesystem cache is bypassed


In all my tests i've never seen the cpu usage go above 100%, ( with 8 cpu's you can go to 800%) i've seen it.
blockio is the current default and fileio is unusable because of initialization failing after 3 iscsi volumes.

My advise is to go for with and

a fast dual single core machine
2~4 GB of memory
a good raid controller ( i use a areca 1230ML 12 disk )
good ethernet controllers ( dual intel server e1000 )


when reading large chunks of data from the open-e san i get the bonded dual e1000 full ( 200+ Mb/s)
when writing large chunks of data to the open-e san I get 100Mb/s
when reading & writing I get on 1 interface i get 100Mb in and out of it, using the full duplex

[derkgort]

Update of my previous post

I've done some testing and i see that there is a difference in IOps when using 1 CPU instead of 8. There is a decrease in speed. my gues is 10 - 50 % drop. It depends on the size of the io size you are reading/writing.

So multiple CPU's are beter then one. How many is useful is still being tested.