Just bought a new X15 server which comes pre-built with a 1TB internal boot drive. The boot partition uses about 32GB which leaves about 99.5% of the drive unused. I’m trying to decide what to do with the unused space. Currently I’ve added it as a 2nd cache drive. I already had one in my old machine (500GB 2.5” SSD) and didn’t really need a second one though.

I’m a little hesitant to use the unused space as a cache because I’m worried that the extra read/writes will wear out the drive faster, so was thinking about getting a smaller m.2 nvme for the internal boot drive and another 1TB m.2 nvme to use in a 2 drive cache pool (replacing my old single disk cache).

One problem I’m seeing with this plan is that nobody seems to make a small (32GB) m.2 drive. The smallest I can find is 128GB and those are all from manufacturers I’ve never heard of. Looks like the price of the 128GB is low enough that the wasted space isn’t really a concern though.

Anyone have any thoughts? Recommendations for m.2s? Better ways to use the current unused space?

16GB Optanes are a common choice.

https://www.ebay.com/itm/375486928506?_skw=intel+optane+16gb&epid=936935701

I'd probably get a 2nd 1TB and make a common mirrored pool for boot and cache though, getting rid of the 500GB.

Edited May 25May 25 by Kilrah

7 minutes ago, Kilrah said:

16GB Optanes are a common choice.

https://www.ebay.com/itm/375486928506?_skw=intel+optane+16gb&epid=936935701

I'd probably get a 2nd 1TB and make a common mirrored pool for boot and cache though, getting rid of the 500GB.

Yeah, maybe that would be best. It looks like it’s not currently possible to replace one internal boot device with another one.⁉️

Google is telling me an internal boot device can only be replaced with a flash drive. Hopefully that will change at some point. I know internal boot is new and hopefully still developing.

So all the read/writes on the 2nd partition on the internal boot device won’t have an effect on the boot partition?

You can replace a device from a mirrored pool (same size or larger). You can also add a new device to a single boot pool, then remove the other one (again, same size or larger), to replace it with a smaller device, you can boot from a flash drive, then run the wizard to create the boot pool on the new device

https://forums.unraid.net/topic/198440-73xx-version-moving-boot-drive-nvmessd-to-another-drive-nvmessd/#findComment-1619744

3 minutes ago, JorgeB said:

You can replace a device from a mirrored pool (same size or larger). You can also add a new device to a single boot pool, then remove the other one (again, same size or larger), to replace it with a smaller device, you can boot from a flash drive, then run the wizard to create the boot pool on the new device

https://forums.unraid.net/topic/198440-73xx-version-moving-boot-drive-nvmessd-to-another-drive-nvmessd/#findComment-1619744

So the key file is transferable to a flash drive and then to a new internal boot drive?

After spending most of 3 days restoring from configurations that were lost during migration to the new X15 hardware I think it’ll be a while before I take this risk again. As long as read/writes on one partition on the boot drive don’t effect the other partition it’ll be a lot easier just to add another 1TB m.2 and create a pool with the unused space on the internal boot drive as suggested by @Kilrah .

20 minutes ago, wgstarks said:

So the key file is transferable to a flash drive and then to a new internal boot drive?

You don't need to transfer the key, you can boot from a flash drive and still use the TPM key.

2 minutes ago, JorgeB said:

You don't need to transfer the key, you can boot from a flash drive and still use the TPM key.

Good to know. So if there isn’t a key file on the flash Unraid will check for a TPM key on another drive.

42 minutes ago, JorgeB said:

You can also add a new device to a single boot pool, then remove the other one (again, same size or larger)

I see that my current internal boot partition shows as 32.2 GB so can I just create a pool with a slightly larger drive (maybe 64 GB) and then remove the 32.2 GB) partition from the pool? I think that would be easier if I’m understanding correctly.

And maybe the wear and tear isn’t worth worrying about? Google says that with typical daily use most m.2 drives will last 60 to 80 years.

In 80 years I’ll be 147 years old and probably won’t care about a drive wearing out.😁

1 hour ago, wgstarks said:

Good to know. So if there isn’t a key file on the flash Unraid will check for a TPM key on another drive.

Nope, you must copy the key file to the flash drive, see the link above.

1 hour ago, wgstarks said:

I see that my current internal boot partition shows as 32.2 GB so can I just create a pool with a slightly larger drive (maybe 64 GB) and then remove the 32.2 GB) partition from the pool? I think that would be easier if I’m understanding correctly.

No, because the data partition is also mirrored when you add a second device. so it would need to be 1TB.

You can add a device just large enough to cover the boot partition if you erase the data partition first (all data there woudl be lost).

30 minutes ago, JorgeB said:

You can add a device just large enough to cover the boot partition if you erase the data partition first (all data there woudl be lost).

The data partition isn’t being used right now so this should be fairly easy. Do you have a link to a description of how to do this?

Click on the data partition and then "Erase Pool" (it won't erase the boot partition)

Then set the filesystem to "auto"

3 minutes ago, JorgeB said:

Click on the data partition and then "Erase Pool" (it won't erase the boot partition)

Then set the filesystem to "auto"

And then I could add a new 32G m.2 to the boot pool and remove the original boot partition?

54 minutes ago, JorgeB said:

because the data partition is also mirrored when you add a second device. so it would need to be 1TB.

Does this mean that I couldn’t create a mirrored cache pool using the cachenew partition I created with the unused space?

14 minutes ago, wgstarks said:

And then I could add a new 32G m.2 to the boot pool and remove the original boot partition?

Yes, if it's same size or larger than the current boot pool, I see the GUI reporting 32.2GB for the current boot partition, so 32Gb may not be enough

32 minutes ago, JorgeB said:

Yes, if it's same size or larger than the current boot pool, I see the GUI reporting 32.2GB for the current boot partition, so 32Gb may not be enough

Sounds like the simplest solution would be to just get a 1TB m.2 and create a mirrored cache pool with the 966GB btrfs partioned space on the original m.2 if that’s possible?

That's possible.

15 hours ago, wgstarks said:

And maybe the wear and tear isn’t worth worrying about? Google says that with typical daily use most m.2 drives will last 60 to 80 years.

Google's answer depends entirely on how you frame the question.

Ask about typical consumer NVMe longevity in a laptop or desktop and you'll get the 60-80 year figure based on light daily workloads.

Ask about QLC NVMe endurance under sustained 24/7 server cache workloads and you'll get a very different answer.

The Kingston NV3 in your X15 is QLC NAND.

QLC has the lowest write endurance of any flash type -- roughly 100-150 program/erase cycles per cell versus 1000+ for more durable 3D TLC.

Under sustained cache activity it degrades significantly faster than the typical consumer use case those longevity estimates assume.

Whether that matters in practice depends entirely on your actual cache write volume over time.

The mirrored 1TB pool approach is probably the most pragmatic path forward -- at least a mirror means a single drive failure doesn't take both your boot partition and cache data simultaneously.

2 hours ago, Lolight said:

The Kingston NV3 in your X15 is QLC NAND.

QLC has the lowest write endurance of any flash type

What has the best endurance?

1. Intel Optane (3D XPoint) -- Best by far.

   16GB or 32GB Optane drives have essentially unlimited endurance for Unraid’s boot workload.

   They’re the gold standard.

2. Higher end 3D TLC (e.g. Samsung 970/980/990 Pro, WD SN850X etc.) -- Good endurance, much better than QLC.

   Still consumer-grade, but significantly more durable than the Kingston NV3.

3. QLC (Kingston NV3, many budget 1-2TB drives) -- Lowest endurance.

   Fine for light desktop use, but not good for 24/7 boot + cache duty.

If you’re committed to a shared NVMe for boot + cache, go with a good 3D TLC drive at minimum.

For the absolute best endurance and peace of mind, dedicated small Optane drives for boot (mirrored if possible) + separate cache pool is the superior configuration.

https://forums.unraid.net/topic/196967-unraid-boot-device-guide-usb-and-nvme-hardware-selection/#comment-1606140

My preferred setup would be a 16GB single disk boot pool (probably Optane) and a pair of 1TB disks in a mirrored pool (raid 1).

Most of my shares don’t use cache so there isn’t a lot writes hour to hour. Probably most of the activity would be databases in appdata (don’t have any VMs).

I’ll probably go with a pair of TLCs for the cache. Looks like I can do that for around $1000.

Seems a waste to have a 1TB nvme I’m not using but I won’t really have any other use for it. I may just mirror it with a 1TB TLC in the cache and replace it when it fails.

1 hour ago, Lolight said:

Intel Optane (3D XPoint) -- Best by far.

16GB or 32GB Optane drives have essentially unlimited endurance for Unraid’s boot workload.

They’re the gold standard.

Ordered a 16GB Optane from Amazon. Will attempt to transfer my boot to this drive as posted above by @JorgeB . The 1TB drive will probably be next month.

On 5/25/2026 at 10:33 AM, JorgeB said:

, to replace it with a smaller device, you can boot from a flash drive, then run the wizard to create the boot pool on the new device

Does it matter if I use the flash from my old system? It has its own key and would still be in sync with the current system except for network settings.

As long as it has 7.3.0 and you don't mind overwriting the old config it's fine, because you should still sync the current config to that flash, or it will also be out of date after creating the new boot pool.

12 minutes ago, JorgeB said:

As long as it has 7.3.0 and you don't mind overwriting the old config it's fine, because you should still sync the current config to that flash, or it will also be out of date after creating the new boot pool.

Not an issue since I currently have no plans to reuse the old machine. I’ll probably back it up though.