Freenas 8 - NFS - ESXi and Latency expected performance

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auromed

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Jun 17, 2011
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I'm quite new to both freenas and esxi, but wanted to know if some of the results I am seeing are normal, or if I should dig into tuning (if that will help).

My freenas setup is as follows:
Code:
OS Version:	FreeBSD 8.2-RELEASE-p2
Platform:	Pentium(R) Dual-Core CPU E6300 @ 2.80GHz
Memory:	3301MB
System Time:	Sat Jun 18 02:51:21 EDT 2011
Uptime:	 2:51AM up 2:37, 0 users
Load Average:	0.00, 0.01, 0.10
FreeNAS Build:	FreeNAS-8.0.1-BETA2-i386


The freenas system has 6 - 1 TB drives with 3 on the motherboard SATA controllers, and 3 on an SiI3124 based add in card.

There is 4GB of ram on the freenas MB, but I am guessing it shows 3301 as thats what is available to the filer portion of the system.

I have a 1Gb switch that connects the freenas box to a Dell T110 II server running esxi. The esxi box has a 250gb hard drive internal to itself as one datastore and the NFS share from freenas as another.

My question surrounds the latency I should expect to see from a datastore standpoint from the esxi box. I have been using a CUCM (Cisco Callmanager) install to test real world performance of the datastores and different configs, and while throughput is good the latency is a bit troubling.

During the install, from the esxi standpoint I see the following average write latencies:

Installing CUCM to local datastore: 15ms
Installing CUCM to freenas (all 6 drives striped zfs): 389ms
Installing CUCM to freenas (pool of 2 sets of 3 drives in raidz): 2893ms
Installing CUCM to freenas (all 6 drives in one raidz volume): 4732ms

The CPU utilization on the freenas box never gets above 50%, so I'm wondering if this is just to be expected with a NAS. I know zfs requires a good bit of RAM to get good performance, so is that probably my bottleneck? Unfortunately the motherboard in the freenas box only supports 4GB, so I can't upgrade that.

Any suggestions to tweak the system?
 

auromed

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Jun 17, 2011
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I also forgot to mention that the CUCM install is always the only vm on the NFS datastore, while the local drive also had a windows xp vm running on it at the time of the tests.
 

aradke

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Sep 2, 2011
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Poor FreeNAS 8 NFS performance

We found similar results with NFS on FreeNAS 8. Latencies under ESXi are in the order of 1000s of ms and performance on the guest VMs was abysmal.

Switching ESXi to using iSCSI saw the same machine have their latencies drop to 2-4ms when busy. We would prefer to use NFS so that the ESXi hosts can share one storage pool but it obviously isn't usable.

On a related note, our Linux servers backup to an NFS share on the FreeNAS 8 box too and find similarly bad performance to ESXi. Since backups aren't so worried about latency issues it isn't a real issue for us but it does show the problem isn't limited to ESXi. My personal FreeNAS 0.7.2 box at home does not suffer from this issue at all.
 
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