NVME M.2 Advice for SLOG/L2ARC

[Donny Davis]

Hello Fellow FreeNASers,

I am looking to put my PCIE NVMe cards to good use, and I would like to use them for a SLOG or L2ARC. Whichever is more appropriate. Currently I have Samsung SM951 128GB in them.

So I will get to my question.

Are there any M2 NVMe cards out there worth their salt for the $subject use case?
Is anyone else doing this, and what is your use case?

Thanks for your time

 

[tvsjr]

Well, you didn't post your hardware configuration (as required), so we're sort of guessing.

Are you doing anything that's highly demanding of sync writes (like presenting storage to ESXi via iSCSI or NFS)? If not, you don't really need a SLOG.
How much RAM do you have in your FreeNAS box? Have you maxed out the motherboard already? If not, you should do that (or at least reach a fairly high number - 128GB or better) before adding L2ARC. Remember, L2ARC will increase memory pressure on RAM... if you have minimal RAM and try to add an L2ARC, you can actually make things worse.

 

[nightshade00013]

Pretty much what tvsjr said is correct. Unless there is a very specific reason for it other than "I have it so lets use it" you are probably better off doing something else with it. Now if it's just hardware sitting around and you don't really need it I am sure I know someone who CAN put it to good use.

 

[Donny Davis]

Sorry about not posting the details of my system. Makes sense.

The workload is mostly VM via KVM hypervisors. I have 12 kvm hypervisors that will run many different types of workloads.

Build FreeNAS-11.1-U1
Platform Intel(R) Xeon(R) CPU E5645 @ 2.40GHz
Memory 98257MB

35 Spinning Rust drives, one Intel DC3610 SSD, and one PCIE NVME card. I can put whatever NVME M2 device in there I want.

Which brings me back to my original question, What is a good NVME M2 drive for SLOG purposes. I do need a SLOG, and maybe possibly benefit from L2ARC.

Thanks for your time :)
~D

 

[nightshade00013]

https://www.servethehome.com/buyers...as-servers/top-picks-freenas-zil-slog-drives/

 

[Donny Davis]

@nightshade00013
Thank you for the link, however I didn't see any M2 drives.

 

[joeschmuck]

@nightshade00013
Thank you for the link, however I didn't see any M2 drives.

From that article in the link:

While you may be tempted to get a NVMe m.2 SSD, the options with power loss protection are very hard to find as of this writing.

So you need a SSD with power loss protection, this is key.

EDIT: You could use the m.2 for the L2ARC if you wanted to, you don't need power loss protection for this purpose.

EDIT2: And your Intel DC3610 SSD would be your ZIL/SLOG as it has power loss protection. Hum, you have all the parts, I think you just wanted to put them in backwards.

 

[tvsjr]

That article appears to be a bit dated. All of the Samsung "Enterprise" and "Data Center" drives currently manufactured - namely the SM963 for M.2 form factor - support power loss protection. The Intel S3520 and P4501 also have PLP, with the P4501 being the preference since it's true PCIe, not SATA.

I would be fairly careful with M.2 stuff today... there are all sorts of issues where drives are SATA rather than pure PCIe (less bandwidth, more overhead), controllers only have 2 PCIe lanes attached versus all 4, etc.

 

[nightshade00013]

Last updated 2017/10/07

 

[Stux]

Intel Optane PCIe cards