Drive configuration

[Kalsto]

I've been doing a lot of reading and I'm just trying to make sure I'm making a solid decision on my drive configuration.

I have 8x 4Tb WD Red NAS drives
I have 5x 4Tb Seagate Barracude

My primary desire is media storage, so more capacity is ideal. Secondary, I'd like to have some vmware storage presented via iscsi..

I've contemplated doing 2x 6 drives in raidz, with one spare.. but because the WD are 5400rpm, and the seagate's are 7200rpm, I thought maybe I'd be better off doing 2x 4drives with the WD, then either buy 3 more seagate and do the same 2x 4drives, or 2x2 drives with one spare.

Any suggestions?

 

[Chris Moore]

I'd like to have some vmware storage presented via iscsi..

It really depends on how important speed of random IO on your block storage is. More vdevs = more speed.
Capacity also enters into the discussion. How much storage capacity do you need?
You might want to do a pool that is RAID-z2 for your mass storage (movies, etc) and do a pool of mirror vdevs for your iSCSI. Faster spinning disks usually makes for less latency, but you will probably want a SLOG device to help speed up the iSCSI pool.

With the disks you have, I would make the WD Red drives into a RAID-z2 pool for the other mass storage and get 3 more Seagate drives to setup a pool of fast spinners in mirrors for the iSCSI.

Would you like to know more?

 

[Kalsto]

Thanks Chris - that sounds like about what I was anticipating.. I'll start with the 2x 4 drive vdev pools for media storage, and look at getting additional faster spinners for the iscsi storage.

I know that recommended SLOG devices have power backup.. but if I'm willing to accept the risk, could I use just about any SSD I have that has decent performance? I have a 256Gb Samsung 840 Pro currently sitting spare on my desk.

Also, I should be able to start with 2x2 drives for the faster spinners, then increase the iscsi pool as I acquire more drives (in groups of 2), correct?

 

[Chris Moore]

I should be able to start with 2x2 drives for the faster spinners, then increase the iscsi pool as I acquire more drives (in groups of 2), correct?

Correct.

I know that recommended SLOG devices have power backup.. but if I'm willing to accept the risk, could I use just about any SSD I have that has decent performance? I have a 256Gb Samsung 840 Pro currently sitting spare on my desk.

You could, but there is the consideration of speed. You could be limited by the speed (latency) of the SLOG device.
One of the suggested options for a SLOG drive is a Intel Optane SSD 900P:
https://www.newegg.com/Product/Product.aspx?item=N82E16820167437
It has the following specs:

• Max Sequential Read: Up to 2500 MBps
• Max Sequential Write: Up to 2000 MBps
• 4KB Random Read: Up to 550,000 IOPS
• 4KB Random Write: Up to 500,000 IOPS

It costs a good bit, so if you are on a tight budget, I can see why you would want to skip it. I am just saying that it is the blinding speed of these devices (in addition to other factors) that make them so desirable to accelerate the block storage.

 

[Kalsto]

Good morning Chris,

That is indeed one helluva speedy device.. my little Samsung hand-me-down doesn't really compare at all.. I'll put the pool in place, run some benchmarks, and see where I'm at. I would like the vmware to have some decent storage performance, but at the moment it's all on a hardware raid (and I don't even remember what raid it's in..I haven't touched it in 7 years...lol), so I'm sure I will see some decent (or at least similar) performance right out of the gate using freenas.

Thank you again Chris - your wealth of knowledge is greatly appreciated!

 

[Chris Moore]

so I'm sure I will see some decent (or at least similar) performance right out of the gate using freenas.

There are a lot of differences with FreeNAS vs using a hardware RAID because FreeNAS is copy on write and if you are doing sync writes it will be slow because the write won't be finished until it is flushed to the spinning rust. That increases latency and makes the iSCSI block storage pretty slow and this is the reason for the super fast SLOG, which makes it fast. With the SLOG device, the sync write is complete as soon as it goes into the SLOG (very fast) and then FreeNAS moves the data onto the HDD at the slower speed of the hard drives, "behind the scenes".

Would you like some links to documentation?

 

[Kalsto]

Hi Chris - I'll see if I can find some docs... Trial and error is some of the best ways to learn. :)

 

[Chris Moore]

Hi Chris - I'll see if I can find some docs... Trial and error is some of the best ways to learn. :)

We have had some really good discussions on configurations to support ESXi lately. You might find some pearls of wisdom here:

There is some great advice in this thread and references to other good threads:
https://forums.freenas.org/index.php?threads/freenas-for-iscsi-vmware-esxi-storage.61651/

This user was also asking about iSCSI for virtualization, but they are trying to do it on a tight budget.
https://forums.freenas.org/index.php?threads/backing-to-freenas-help-with-topology.61659

Then this one is one of my favorites because he goes into so much detail with photos and documentation. @Stux is very knowledgeable.
Build Report: Node 304 + X10SDV-TLN4F [ESXi/FreeNAS AIO]
https://forums.freenas.org/index.ph...node-304-x10sdv-tln4f-esxi-freenas-aio.57116/

 

[tvsjr]

The Optane 900 was determined to NOT have PLP:
https://ark.intel.com/products/1236...Series-480GB-12-Height-PCIe-x4-20nm-3D-XPoint

Depending on the size of the iSCSI store desired, I'd consider just putting two fast, PLPed SSDs in a mirror. That's what I'll do when Optane 4800Xs get cheaper.

 

[IQless]

If the OP decides to start off by adding that 840 Pro as SLOG, then later on wanting to change that to a P3700. Is it straight forward to just remove/detach the existing SLOG and then adding the new one? or is there pitfalls to be aware of? (asking for a "friend"... :P)

 

[Chris Moore]

If the OP decides to start off by adding that 840 Pro as SLOG, then later on wanting to change that to a P3700. Is it straight forward to just remove/detach the existing SLOG and then adding the new one? or is there pitfalls to be aware of? (asking for a "friend"... :p)

Yes, you can safely remove a slog device. Here is a thread that tells you how:
https://forums.freenas.org/index.php?threads/safely-remove-slog.50999/