Can I boot from DOM and mirror it with USB? (2025)

I have a motherboard with one DOM port.
Id like to use all my other regular SATA ports for ZFS and boot from the DOM instead.

Im thinking about mirroring the DOM (my OS boot drive) to an external USB, just in case.
Is that a good approach compared to booting directly from USB and mirror it with another USB?
I was going to go only USB, but I saw this article about USB bootable devices.
https://www.ixsystems.com/blog/sata-doms-over-usb-drive/

Dotty said:

I have a motherboard with one DOM port.
Id like to use all my other regular SATA ports for ZFS and boot from the DOM instead.

Click to expand...

A SATA DOM is a fine option, just get a good quality model, like the ones from Supermicro.

Dotty said:

Im thinking about mirroring the DOM (my OS boot drive) to an external USB, just in case.

Click to expand...

I would think that would actually introduce a greater potential for failure. USB media has a history of near random failure and when it fails it is not graceful or predictable. Also, when the USB module fails, it often causes a system lockup / crash. I would think the DOM would be more reliable alone than using the two together.

Chris Moore said:

A SATA DOM is a fine option, just get a good quality model, like the ones from Supermicro.

I would think that would actually introduce a greater potential for failure. USB media has a history of near random failure and when it fails it is not graceful or predictable. Also, when the USB module fails, it often causes a system lockup / crash. I would think the DOM would be more reliable alone than using the two together.

Click to expand...

Another option I was considering is getting a NVMe to PCI card and boot from there instead of DOM, but IM not sure if my motherboard or FreeNAS would let me do that.
How that would compare to the DOM? (in terms of performance and endurance)

Dotty said:

How that would compare to the DOM? (in terms of performance and endurance)

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Performance isn't that important for a boot drive. It isn't accessed that much and the things it is accessed for are not very time sensitive.

Dotty said:

Another option I was considering is getting a NVMe to PCI card and boot from there instead of DOM, but IM not sure if my motherboard or FreeNAS would let me do that.

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I tried to boot from a NVMe drive on my Windows workstation and I could not get it working because the system board did not support booting from the NVMe drive, so that is going to depend on your hardware to a great degree.
What I have done in all the NAS systems I have built is use a SAS controller to connect all the storage drives and reserve the SATA ports on the system board for only the boot media. It works well for me. At home, I am using a mirrored pair of mechanical drives for boot media but at work I have configured the boot pool on a mirrored pair of Intel SSDs. I do have a couple systems that were delivered with SATA DOMs and I rebuilt them to run on FreeNAS instead of their original OS. It depends on what options you have.
I don't think the boot pool is "worth" the cost of a NVMe drive, even if you could make it work.

Is this for the same system that you have been looking into building? It's a 2U rack chassis, right? Did you get the hardware in-house yet?

Dotty said:

Yes, I did get it, and Im using all the front bays for data, reserving the rear 2.5 bays for VMs an future use, so i need something to boot from.
I don't wan to sacrifice the rear bays for OS.
Most likely I will order a SM DOM, Newegg has them.

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What system did you actually buy?
Is there no SAS controller in the system?
I would love to see details so I can get some options for you.

Chris Moore said:

What system did you actually buy?
Is there no SAS controller in the system?
I would love to see details so I can get some options for you.

Click to expand...

6027R-E1R12L , and has a X9DRD-7LN4F-JBOD motherboard on it and I added a 9211-8i on IT mode.

https://www.supermicro.com/QuickRefs/motherboard/C606_602/QRG-1318.pdf

In this image, the top left corner of the board, there are two SAS connections to the system board's integrated (IT mode) Broadcom 2308 chip. Between that and the 9211-8i on IT mode card you added, all the front and rear bay drives can be connected to SAS, so all the SATA ports on the system board can be used for the boot media. Just get two SATA DOMs. I see what you mean that there is only one power header for a SATA DOM, but you can get a Molex adapter:
https://www.ebay.com/itm/Power-Cabl...SATA-DOM-1pin-not-connect-10-pcs/253852805272
or
https://www.ebay.com/itm/SATADOM-Po...connector-to-2-pin-SATADOM-power/283448905716

Dotty said:

Where do I physically put the two DOMs inside the chassis?

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SATA DOMs plug into regular SATA ports. The board has six SATA ports. The thing it only has one of is the power port to connect the DOM to 5 volts.

Chris Moore said:

The board has six SATA

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They seem to be packed and if I'm not wrong DOM drives are bigger/wider/thicker than SATA data connectors. Would a data extension cable be a good solution? And the DOMs physically mount using e.g. velcros?

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pro lamer said:

They seem to be packed and if I'm not wrong DOM drives are bigger/wider/thicker than SATA data connectors. Would a data extension cable be a good solution? And the DOMs physically mount using e.g. velcros?

Sent from my phone

Click to expand...

They are packed, and looks to me that they wont just allow for putting a DOM just there, so most likely I will test and see what happens.
But I rather have them to look neat. Usually Ugly=Unsafe
If I have to put velcro or anything else I rather use regular SATA drives inside the chassis, the velcro defeats the purpose of using DOM.

Some chassis have space and sometimes mounting holes for additional 2,5 drive cages. Some have dedicated cage types. Dunno if this one too but looking for one or asking might be worth a try...

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