seek a suggestion - my spare SSD cache

[anchen]

Hello Community,

PS: this post was initially put at a wrong place. my bad.

I need some advise of how to use my spare SSD with FreeNAS.

my setup

1) HP Microserver gen10 with 4 core CPU, 32G ECC RAM. I do not have video card, and 10G card etc.
2) 4 x 6TB WD NAS drive
3) FreeNAS running on a HPE 8G USB drive. ( Yep, I format that stupid ClearOS, and repurpose the 'enterprise grade' USB stick :).

My use case

1) Home NAS, time machine backup, video/photo, file storage.
2) my lovely movie collection
3) emby server running on the FreeNAS as a plugin. No VM, No other plugins.

My Question

I have 2 x SSD spare, which I can connect to HP Microserver ( use 1->2 SATA connector etc ). 1 x SSD is Samsung old 1TB (approx 5 years old). another SSD is Intel 128G ( approx 5 years old as well). They both functioning very well.

My understanding is that for FreeNAS, we can add a read and write cache. So I am wondering, should I consider to use those SSD one for read, and one for write cache. If so, seeking fellow's suggestion which one suits for read, and which for write.

Alternative, would you suggest to make an new pool with SSD, and host emby plugin on SSD pool, rather than the HDD pool which assuming would get better performance if needs load a lot movies etc.

Thank you so much.

Andy

 

[sretalla]

3) FreeNAS running on a HPE 8G USB drive.

Replace this with the 128GB SSD

You probably don't have enough RAM to make sense to add L2ARC. Those SSDs are not good candidates for SLOG.

Use the 1TB SSD for Jails and/or Jail config/DB datasets (sort of as you're suggesting.

 

[Yorick]

My understanding is that for FreeNAS, we can add a read and write cache

SLOG is not a write cache. It’s a way to mitigate the performance impact of sync writes, which you are not using.

L2ARC is a read cache, which comes into play when your work set wouldn’t fit into ARC. Run zfs-stats -a and look at your ARC hit and miss rate. Most likely, you are fine, and have no reason to use an L2ARC.

There are specific use cases where an L2ARC can help, such as rsyncing tens of thousands of files with not enough ARC for metadata - but the use cases you describe don’t seem to fit that.

For almost all home use cases, you are best off without L2ARC, and certainly without SLOG. This rule of thumb should serve you well: If you cannot define how either would benefit you, in granular technical detail, and point at the specific performance bottleneck that will be solved and how it will be solved, you are better off not adding them.

 

[SweetAndLow]

You don't need either. The l2arc might even hurt performance.

 

[anchen]

Hi All,

Thank you so much for those feedback. I will not consider those cache things anymore, and use 128G SSD for the boot disk for the FreeNAS, and 1TB SSD for the Jail pool.

Thansk.

Andy