FreeNAS SAN for ESXi Storage

[Slu]

Hello all,

Just a quick question that I could use some advice on. I currently have a FreeNAS server that I'm building with 12 2TB hard drives that I will be using as a SAN for 3 ESXi servers.

My question is what is the best way to set up the zpool for mirroring? I originally was going to go with 2 Vdevs(6 drives each) with RAID-Z2 in one Zpool but I was told here on the FreeNAS forums that for what I'm doing I should do mirroring instead to improve performance.

So, which of these three options is the best?
1) Set up 2 Vdevs with 6 drives each, with Raid 1 on each Vdev?
2) Set up 6 Vdevs, with 2 drives each, Raid 1 on each Vdev
3) Set up 1 Vdev, with all 12 drives on it, Raid 1.

I will also be implenting mirroed SSD ZILs and using ISCSI.


Thank you so much for your time and assistance in advance!

 

[gpsguy]

Six vdevs of 2 drives each (mirrored).


Sent from my phone

 

[Slu]

I see. Thank you. But, then if one drive in one Vdevs fails, I would have to immediately replace that drive because if that other drive fails, I'd lose the vdev which mean Id lose the whole Zpool....
That's a bit scary.

 

[depasseg]

If you don't have replication setup and are more concerned with data protection (over performance), then use RAIDZ2. But be prepared for very slow VM's.

 

[Slu]

Thank you.

I have a replication solution in place using unitrends. However, I was just reading that in order to replicate data from FreeNAS, but systems require a zpool...

I'm unsure if unitrends handles freeNAS type systems. All of our current servers run either Linux or Windows...I have to inquire.

 

[Ericloewe]

I see. Thank you. But, then if one drive in one Vdevs fails, I would have to immediately replace that drive because if that other drive fails, I'd lose the vdev which mean Id lose the whole Zpool....
That's a bit scary.

You can also do three-way mirrors.

Unfortunately, there's no good solution. You can pick any two of speed, cost and reliability.

 

[Darren Myers]

If youre gonna use iSCSI youre gonna have a bad time, remember not to use more then 50% of your iSCSI pool/vdev's due to fragmentation.

 

[Slu]

We're a pretty small enterprise, 150 users. With only 8 VMS running on our 3 esxi servers.

Is Raid-Z2 really gonna be that big of a performance hit?

 

[cyberjock]

If you don't have replication setup and are more concerned with data protection (over performance), then use RAIDZ2. But be prepared for very slow VM's.

True, but only until the latency goes high enough that the ESXi hosts think the storage server is offline. Then all the VMs go offline and the admins will then have what we would call "a bad day".

We're a pretty small enterprise, 150 users. With only 8 VMS running on our 3 esxi servers.

Is Raid-Z2 really gonna be that big of a performance hit?

Yes, it is generally very crippling. Running more than 2-3 VMs will be devastating to performance. If you buy a system from iXsystems and plan to run VMs with it they strongly recommend mirrors. If you go with something else (and many people try because of the obvious cost savings) they are virtually guaranteed to have problems. Unfortunately for them, they don't always understand the problem until it is too late and they have to migrate all of their data off so that they can rebuild the zpool.

If you plan to run 3 ESXi servers off of FreeNAS, you have no options except to do mirrors. Anything else will not be able to handle the workload of a single ESXi server, late alone 3 of them.

 

[Slu]

Okay,

Sounds like I'll be going for the 6 vDevs with mirrors. I just have to reach out to unitrends(my replication/backup enterprise solution) to see if they handle FreeNAS. Cause what I read was that their back up systems would have to be configured with a zpool as well to handle the replication.

Final question. I was reading that in order to properly do this over iSCSI, jgreco mentioned that you must implement " Set 'sync=always' on the dataset". How exactly is this done? That sticky post does not explain it.. nor do the docs talk about it...

 

[Slu]

Hey All,

So I'm about to configure this today and I seem to have confused myself...
According to your recommendations, I should be doing 6 vdevs(2 HD's Each)

However, I seem to be confused on how exactly I would set this up. Please see the screenshot below. Is this how I would do it? Or do I need to do 2 drives at a time?
Thank you so much for all your help.