Metadata vdev and over-provisioning of SSD drives.

[terry5008]

Hello,

I've noticed that the TrueNAS-CORE doc hub gives instructions on SSD over-provisioning(OP) of a SLOG via System > Advanced > Storage, but does not cover a solution for SSD OP of a Metadata vdev. My questions are as follows:

1. Is there a way to OP Metadata SSDs even if it means using CLI or OS shell commands?
2. Am I making this too complicated? Should I instead just do the OP SLOG and set all writes to sync writes?
3. If I do the OP SLOG, how do I verify that it IS in fact doing what I configured it to do? Does the setting in System > Advanced > Storage cause a SLOG partition to be created of the stated setting size that can be viewed with another tool?

Thank you in advance for your assistance.

 

[winnielinnie]

For others to be able to better help (or provide feedback): What are you trying to accomplish?

A SLOG and a Special Metadata vdev are two completely different things with different properties and uses. Your post makes it sound like you're okay with using one or the other? (Which doesn't make sense.)

 

[terry5008]

For others to be able to better help (or provide feedback): What are you trying to accomplish?

A SLOG and a Special Metadata vdev are two completely different things with different properties and uses. Your post makes it sound like you're okay with using one or the other? (Which doesn't make sense.)

Just experimenting with the product to see what performance enhancements can be achieved with SSD drives for a general-purpose home NAS storing media, documents, music, and running various plugins. This is not a commercial or mission-critical application.

From what I've read, the SLOG can really shred an SSD, and I'm wondering if the same is true of the metadata vdev. But as I stated, there is no documented way of doing OP on a metadata vdev(that I have found).

I have however found the answer to question number 3. Go to the shell and type gpart list.

 

[terry5008]

For others to be able to better help (or provide feedback): What are you trying to accomplish?

A SLOG and a Special Metadata vdev are two completely different things with different properties and uses. Your post makes it sound like you're okay with using one or the other? (Which doesn't make sense.)

So..., any ideas on number 1? It's a rather straightforward question. No need to know my motives or hardware.

 

[Etorix]

1. If the drive allows over-provisioning (e.g. Optane DC), you can over-provision it by whatever tool it takes, within or outside of TrueNAS.
2. As said, SLOG and metadata are two different things, completely orthogonal to each other. A SLOG, in a sync write workload, is constantly written to, and retains nothing; it requires high-endurance. Metadata is part of data; a metadata vdev is NOT subject to constant rewrites, retains data, and is subject to the same endurance requirements as the rest of the pool (read-intensive SSDs are likely fine).

You are likely over-thinking it—and most likely mis-thinking.

 

[Davvo]

From what I've read, the SLOG can really shred an SSD, and I'm wondering if the same is true of the metadata vdev.

No, the workload is different.