Cache Pool (Metadata) Options

[mlody11]

Hi, I run a btrfs pool of 5 disk for use as an NVR storage and I try to sleep as many disks as possible because 5 disks running non-stop can amount to some electricity. I've been tinkering with things and I'm wondering about options.

 

I noticed that when I write anything to the pool of 5, it spins up all of the drives.  This is presumably because the metadata is setup in a RAID0 configuration.  Is there any way to change that to single when using a cache pool?

 

As an alternative, I noticed synology has an option to move the metadata to a SDD.  Is that a possibility with a BTRFS pool?

 

If we could run two or more "unraid pools," I'd choose that option so here's to hoping that is in the release pipeline

[JorgeB]

14 hours ago, mlody11 said:

I noticed that when I write anything to the pool of 5, it spins up all of the drives.  This is presumably because the metadata is setup in a RAID0 configuration.  Is there any way to change that to single when using a cache pool?

I if you write more than 2Kb it will go to data blocks, not metadata, so yes if it's raid0 it will stripe writes to all drives, you could use single profile but data will still be distributed by all poo drives in 1GiB chunks, according to available space, it will allocated the next chunk to the drive with most space available.

 

 

[mlody11]

So, even if its a single type pool, if I write 10 gb within 15 minutes, it will evenly distribute that 10gb across 5 drives within 15 minutes, effectively stopping any drive from going to sleep. So, it doesn't even matter where the metadata is stored.

Edited February 22, 2022 by mlody11

[JorgeB]

6 hours ago, mlody11 said:

it will evenly distribute that 10gb across 5 drives within 15 minutes,

Correct, assuming they all have similar available space.