Value in Multiple Cores?

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mattlach

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Hey all,

The hardware guide doesn't mention much about core count, so I figured I'd ask here.

Does FreeNAS effectively use multiple cores? Is there a real difference as core count goes up?

I plan on running FreeNAS as a guest under a VMWare ESXi server, and I am trying to figure out how many cores would be a good idea to assign to it.

Useage environment is going to be as follows:

-4 3TB hard drives in Raidz2 configured as an iSCSI target.
-Potentially a couple of mirrored small SSD's for the ZIL
-Potentially a small SSD cache drive.

Load will vary. It will see periods of intense loads from multiple clients, but then also be idle for long periods of time.

Thanks
Matt
 

tingo

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Answer in two parts.
1) Yes, FreeNAS (and FreeBSD) effectively makes use of multiple cores (and multiple cpus for that matter).

2) ESXi (and other virtualization hypervisors) have their own rules. And it depends on the load what makes a "best fit" for a certain function. Unless someone else has already tested this and written the answer somehwere, you will need to test and figure it out yourself. But with ESXiit is easy; give the vm two cores (for example) test performance, then change the number of cores (try one or four, for example) and test again.
Note: if your FreeNAS isn't loading the ESXi server a bit (for example if FreeNAS is idle most of the time), your test results might be wrong.
 

mattlach

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Answer in two parts.
1) Yes, FreeNAS (and FreeBSD) effectively makes use of multiple cores (and multiple cpus for that matter).

2) ESXi (and other virtualization hypervisors) have their own rules. And it depends on the load what makes a "best fit" for a certain function. Unless someone else has already tested this and written the answer somehwere, you will need to test and figure it out yourself. But with ESXiit is easy; give the vm two cores (for example) test performance, then change the number of cores (try one or four, for example) and test again.
Note: if your FreeNAS isn't loading the ESXi server a bit (for example if FreeNAS is idle most of the time), your test results might be wrong.

Thank you for your reply.

I obviously know load will very greatly from configuration to configuration, but how much CPU load should I expect from FreeNAS?

My ESXi 5.1 server is an AMD FX-8120 system with 32GB of RAM.

It has 8 cores, with a base clock speed of 3.1 Ghz, a nominal turbo of 3.4Ghz (all cores fully loaded) and a max turbo of 4.0Ghz (half of cores fully loaded)

The server is my home server, I just use ESXi for consolidation of a few VM's. Currently it is quite underutilized, so each VCPU won't have to switch between cores much.

Configuration will be as follows:
- pfSense Router - 2 vCPU's, 2GB RAM
- Ubuntu 12.04 Server - 4 vCPU's, 4GB Ram
- FreeNAS (waiting for 8.3 Final) - 2 vCPU's, 20GB RAM
- Windows Vista (for testing) - 2 vCPU's 4GB RAM

So in total, 10 vCPU's and 30GB of RAM will be assigned to all VM's. 2GB of RAM will be left unassigned for ESXi to utilize entirely for itself.

Should I expect to see CPU load be significant on this system during intense reads and writes?

Thanks,
Matt
 

JaimieV

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Oct 12, 2012
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Not a lot, no. My dual 1.3GHz AMD box barely hits 50% utilisation (of 200%) while scrubbing and rsyncing to the backup host, while being used - and that's with compression on too. Disk performance (spindle speed and quantity of RAM cache) is more significant than CPU. Your specs there are pleasantly overkill, and RAM allocation can easily be dropped down to half that if you later need it for something else (unless you're going to enable deduplication, which isn't a necessary thing on a home box).

Unless you have the kit going to spare already and want to play, I wouldn't bother with the ZIL SSDs or cache drive - it just adds more parts that might go wrong. My primary NAS gets about 80meg/second over GigE with just 4x2Tb RAIDZ1, 5gig RAM and no addons (HP Microserver N36L), and there's not a lot more headroom in GigE. It doesn't seem to bog down.
 

joeschmuck

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And the good thing about the VM is you can change the number of cores and RAM at any time. It's not like Windoze where it may trigger a registration event or cause any problems. You could start big and then start dropping down your resources over time to see if you see any performance hit. I still think 8GB RAM and 2 cores are fine and see what how it works.
 

cyberjock

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8GB of RAM and 2 cores is an excellent start. But expect your CPU loading to be near maximum when doing a scrub.
 
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