Is it possible to setup L2ARC and ZIL on the boot drive?

[xuegy]

Hello all,

I put a 32GB Intel Optane into the m.2 slot as the boot drive. However, I noticed that around 25GB is wasted. Is it possible to utilize these empty space as the cache?

Thanks.

 

[kdragon75]

I put a 32GB Intel Optane into the m.2 slot as the boot drive.

Yeeaahhhh.... About that.... You should get a cheap SSD and boot from that, and then we can talk about splitting the drive for SLOG and L2ARC.

In short, No. It's not possible.

 

[HoneyBadger]

Is it possible to utilize these empty space as the cache?

No, it's not possible. FreeNAS claims the entire device assigned to booting and it can't be used for any other purpose.

@kdragon75 is correct in that you should use a cheap SSD (or perhaps a mirrored pair of USB drives) for boot, and then talk about using the M.2 slot for other purposes. Although I'd suggest that 32GB isn't enough capacity to be worthwhile as L2ARC (and your workload probably doesn't demand it) - just make it an SLOG only device.

And hey, blatant plug - think you could pop into this thread and run the diskinfo benchmark against that Optane drive?

https://forums.freenas.org/index.php?threads/slog-benchmarking-and-finding-the-best-slog.63521/

 

[xuegy]

Yeeaahhhh.... About that.... You should get a cheap SSD and boot from that, and then we can talk about splitting the drive for SLOG and L2ARC.

In short, No. It's not possible.

I'm using a Dell PowerEdge T30, with only 4*SATA and 1*m.2. I don't want to waste a native SATA port so I use m.2 to boot. Maybe I should find other ways to attach a booting device.

 

[HoneyBadger]

I'm using a Dell PowerEdge T30, with only 4*SATA and 1*m.2. I don't want to waste a native SATA port so I use m.2 to boot. Maybe I should find other ways to attach a booting device.

WARNING: Do not update your BIOS past 1.0.2 or you will lose NVMe support on your M.2 slot!

https://www.dell.com/community/PowerEdge-Hardware-General/PowerEdge-T30-s-BIOS-problem/td-p/5076821

As far as I can tell this was a deliberate choice by Dell to cripple the system.

Regarding your boot situation, how about mirrored USB as suggested before?

 

[xuegy]

No, it's not possible. FreeNAS claims the entire device assigned to booting and it can't be used for any other purpose.

@kdragon75 is correct in that you should use a cheap SSD (or perhaps a mirrored pair of USB drives) for boot, and then talk about using the M.2 slot for other purposes. Although I'd suggest that 32GB isn't enough capacity to be worthwhile as L2ARC (and your workload probably doesn't demand it) - just make it an SLOG only device.

And hey, blatant plug - think you could pop into this thread and run the diskinfo benchmark against that Optane drive?

https://forums.freenas.org/index.php?threads/slog-benchmarking-and-finding-the-best-slog.63521/

Are USB drives reliable?

WARNING: Do not update your BIOS past 1.0.2 or you will lose NVMe support on your M.2 slot!

https://www.dell.com/community/PowerEdge-Hardware-General/PowerEdge-T30-s-BIOS-problem/td-p/5076821

As far as I can tell this was a deliberate choice by Dell to cripple the system.

Regarding your boot situation, how about mirrored USB as suggested before?

Yeah I downgraded my BIOS to enable the m.2. As for the dual USB device, are they reliable to run 24*7*365 without maintenance?

 

[HoneyBadger]

Are USB drives reliable?

Less reliable than a SATA drive certainly, that's why people concerned with maximum uptime should mirror them (ideally with two different well-known brands) - and updates are a fair bit slower.

If you have a self-powered USB enclosure that can support a small 2.5" SSD that might be another option; you'd still have the USB quirks to deal with (slower interface) but the media itself would be far more reliable.

Good to know you caught the BIOS issue. Nasty piece of work on Dell's part.

As far as the "24x7x365" bit - there's always the potential for a failure, and honestly the odds of a fault in a mirrored USB boot vs. a single SATA boot is probably pretty similar, all things considered. Personally I'd be comfortable with two good-quality (Sandisk, Crucial, etc) USB drives in that scenario; just make sure you take config backups regularly and keep them somewhere external to the box, monitor your SMART alerts and make sure to pay close attention if your freenas-boot pool throws an alert.

The other option is to install another HBA or a PCIe-to-M.2 adapter and drop another card in there for boot.