[LON-CAPA-admin] Server Configuration Questions

[Gerd Kortemeyer]

Hi,

On Jul 9, 2009, at 12:28 AM, Todd Ruskell wrote:
>
> We're getting some new hardware, and that has raised a couple  
> questions I'd like to ask the community:
>
> 1) 32-bit or 64-bit build?  Other than simply being able to access  
> more  memory per core, does that bring real performance advantages  
> in LON-CAPA?  Or are there other real performance advantages to  
> moving to a 64-bit build?  Or is it more like, "hey, it's 64-bit  
> hardware, so why not?"

I would say so. You will have more throughput, and sooner or later,  
you'll have to change anyway.

>  We are currently 32-bit, so moving to 64-bit will require some file  
> conversion, but that shouldn't be too bad.

Yes, this is fairly well tested by now. You have probably already  
found http://www.lon-capa.org/hardwareupgrade.html


>
> 2) As some of you know, our IT folks are moving to a virtualized  
> infrastructure.  We currently have 1 library server and 2 access  
> servers, each of which has dual-core hyperthreaded hardware.   
> Although the servers are virtualized, the above hardware is  
> dedicated to only the designated LON-CAPA server.
>
> The new hardware consists of blade servers with *lots* of cores, and  
> even more memory.  I've already been informed that we can't claim an  
> entire blade each for the library and access servers :( but I can  
> see that would probably be overkill.

This is somewhat odd, though. Virtualized blades?


>
> So finally the question:  If you had the option, which of the  
> following hypothetical situations is "better" for optimal  
> performance?    Would you prefer 1 monster virtual library server  
> with 6 cores and 12 GB of RAM (or more if 64-bit).  Or would you  
> prefer 1 library and 2 access servers, each with 2 cores and 4 GB of  
> RAM (all virtual, most if not all of the time running on the same  
> blade)?

If it's the same blade, make it one monster library server to avoid  
overhead. More servers make more sense if you have dedicated hardware  
and dedicated DISKS.


>  Or is there some other optimal distribution of cores and memory?   
> In either case, the contents of /home are located on a SAN.

Yes, make it one monster library machine. Same blade, same connection  
to the SAN ... makes no sense to split it.


>
> I do know that if we went to the single-server model we'd no longer  
> be able to offer up our access server as spare machine, and we'd  
> also not be able to offload users to another spare machine.

Why not? You can always offload. You can also offer your library  
machine as


>  Are there other reasons to stay away from a single "monster" machine?

Nope.


>
> Back in the day when we were really limited to the number of cores  
> per physical machine, having more than one machine made sense.  But  
> now it seems like having three virtual servers running on the same  
> hardware is just adding an extra, unnecessary layer that slows  
> things down.

That would also be my assessment.

- Gerd.