Is it possible to re-purpose these components for FreeNAS usage?

[Chris Moore]

I was wondering if there is a resource available on how to best configure zvol/zpool. I would like to run 8TB iSCSI, 4TB Windows sharing and 4TB NFS. This will be on 16x2TB drives. Was planning on using stripping/mirroring to get the best performance. Is that a good idea?

For iSCSI you need to keep 50% free space on the pool. So, if you need 16TB useable, the pool needs to be 32TB. That would take 4TB drives instead of the 2TB drives you were thinking or, twice as many drives. More drives will give more IOPS.

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[Chris Moore]

I run multiple pools in my NAS with one pool of mirrors for iSCSI and a second pool for SMB share to the Windows clients.

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[Eric Schrauth]

When you say 16TB usable, are you saying 16TB usable for iSCSI? I was looking to have 8TB usable for iSCSI. I was thinking of having 8 of the drives dedicated to iSCSI and the other 8 to Windows/NFS

 

[Chris Moore]

I was looking to have 8TB usable for iSCSI. I was thinking of having 8 of the drives dedicated to iSCSI and the other 8 to Windows/NFS

I am not sure how you plan to do that. Are you going to create two separate pools of drives with one pool for iSCSI and another pool for the NFS?
If you make a single pool with all 16 drives, in a pool of mirrors; that gives you 8 mirrors but you can't actually use all that space. Partly because it doesn't mathematically exist (a 2TB drive is not actually 2TB) but also because of the overhead that ZFS takes away for checksum data. If you use all 16 drives in a single pool of mirrors it would give you 14TB of practical 'usable' space and you can't fill that beyond 50% without your iSCSI performance tanking. That leaves you with 7TB that you can reliably use out of all those drives. If you want to actually use 8TB, you could, but the performance may suffer. If you then want another 8TB of usable space for NFS shares, you either need more drives or use bigger drives to begin with, instead of 2TB drives, but you still can't fill the pool beyond 50%, so you need to keep a close eye on usage.
If you wanted to use RAIDz2 (or something else) the math may change significantly.
Does that clear it up?

 

[Eric Schrauth]

Does that clear it up?

A little. Is the best performance for iSCSI mirroring?

 

[Chris Moore]

A little. Is the best performance for iSCSI mirroring?

Each vdev has a finite number of IOPS. With mirrors you have more vdevs, which gives you more IOPS.

 

[Eric Schrauth]

Probably a stupid question but I want to understand better. Am I thinking this right:
32TB raw space - 16x2TB drives
~16TB - 1/2 that for Mirroring to make drive access as fast as possible
~8TB - Don't want to go over 50% for iSCSI to work well.
~6.4TB - Want to use only 80% space.
Am I missing something?

 

[Chris Moore]

~8TB - Don't want to go over 50% for iSCSI to work well.
~6.4TB - Want to use only 80% space.
Am I missing something?

50% for an iSCSI pool
80% for a regular NFS share pool.
Normally it is either one or the other.
The reason for leaving the free space is because of the copy-on-write nature of the file system.

 

[Ericloewe]

You do have to consider a factor of roughly 0.909 to convert from the base 10 exponents every HDD is sold in to the base 2 exponents every OS uses.

 

[Mirfster]

If this helps, here is info on an iSCSI Pool of mine:

12 x 4TB Drives (SAS, not that it really matters though)

• 5 x vDevs (Mirrored)
• 1 x 4TB Hot Spare (allocated to the Pool)
  
• 1 x 4TB Cold Spare (non-allocated, IIRC not even plugged in so it doesn't spin)
• 1 x SSD SLOG (250 GB)

So, I at the end of the day I have ~ 16.7 TiB (<--- Notice I did not use "TB")

Out of that available space I will only ever allow 7TiB of space to be used/consumed

• I locked this by setting the "Size" for each zVol; I have 2 zVols. One is for ESXi (which is locked at 4.5TiB) the other is for HyperV (which is locked at 2.5TiB)
  
• Keeps me well below the 50% performance hit for an iSCSI Pool
• I am not concerned about the 80% utilization rule since I can never even get close to that by adhering to the 50% iSCSI rule

TL;DR: Out of 40TB of Raw Space... I will only ever use/consume 7TiB. :)

 

[Eric Schrauth]

One is for ESXi (which is locked at 4.5TiB) the other is for HyperV (which is locked at 2.5TiB)

It does! I was wondering. Why both ESXI and HyperV?

 

[Mirfster]

It does! I was wondering. Why both ESXI and HyperV?

I own a copy of Server 2012 R2 x64 DataCenter, so I can run unlimited Server 2012 R2 VMs (per MS Licensing - Not counting CALs); so that is where I do my main MS Server 2012 R2 stuff.

ESXi is pretty much for any other VMs. My main FreeNAS is even running in there as a VM (not recommended for those just starting out).

However, all "vital" data is not actually housed on the iSCSI Volume; it is housed on a separate Volume (CIFS/SMB) which is owned/controlled by FreeNAS and backed up.

I get to have my cake and eat it too... ;)

 

[Eric Schrauth]

Is the CIFS/SMB on the same FreeNAS unit?

 

[Mirfster]

Is the CIFS/SMB on the same FreeNAS unit?

Yep. For kickers FreeNAS is also my main Domain Controller. I'm not going to pay MS for CALs to have Active Directory. Instead I use the Domain Controller within FreeNAS (Samba). It runs Server 2008 R2 Domain Forest level.

Keep in mind I am a hardware junky and have multiple Servers. So one server is dedicated to running Server 2012 R2 DataCenter and connects via 10GB to the iSCSI Volume. One Server runs ESXi 6.0 and houses FreeNAS (as a VM). FreeNAS has direct (via pass through) access to 3 HBAs and all the drives. A 3rd system is just a JBOD (Just A Bunch Of Disks) that holds additional drives...

There is more, but also note that I currently have a lot of RAM Reserved (specifically allocated) to FreeNAS and more will be added soon.

 

[Eric Schrauth]

When you say a lot, how much are you talking, if you don't mind me asking.

 

[Mirfster]

When you say a lot, how much are you talking, if you don't mind me asking.

96 GB of RAM in the ESXi box right now, with 64 GB strictly allocated to FreeNAS. I am about to up the entire amount to 192 GB for ESXi with at least 128 strictly allocated to FreeNAS.

 

[Stux]

Are you serving the iSCSI volumes from bare metal FreeNAS?

 

[Mirfster]

Are you serving the iSCSI volumes from bare metal FreeNAS?

Who me?

If that was meant for me, then the answer is "no". FreeNAS is a VM that has direct access to the HBAs (thusly all the drives except for the two mirrored ones that ESXi is installed on) and 10GB NICs.

 

[Stux]

Yes, you :)

So, I guess your FreeNAS vm is not hosted on the iSCSI volume ;)

But actually in ESXi local storage right?

 

[Mirfster]

Correct, the FreeNAS VM is hosted on ESXI's datastore; which is only two 120 GB drives that are mirrored.