ceph: can I use multiple device for a pool?

cola16

Member
Feb 2, 2024
34
2
8
I have 3 classes
ssd, hdd, hdd-small(under-1tb)

I want to use HDD and HDD-small in a pool.


SSDs are a class for disk images of VMs only.
The HDD is for storing all other files.
HDD-small is an HDD class to not allow erasure coded pools.

The reason for the split between HDD and HDD-SMALL is as follows
Let me explain what happens if we don't divide them.

The k+m of erasure code is 6.
There are 9 HDDs and HDD-small in total.
There are tree of 3-terabyte HDDs, six of 2-terabyte HDDs, and 3 of 1-terabyte HDDs.
I expected to use 12 terabytes erasure coded pool.
I thought I would be able to use 6 times the capacity of the 6th largest OSD.

But it creates a pool of 6 terabytes.
It creates 6 times the size of the smallest OSD in the HDD class.
So the 1 terabyte HDDs were divided into different classe.

The thing is, I would like to be able to use 1 terabytes osd and 1 terabyte of 3 terabyte osd
In other words, I want to use all the HDDs (HDD+HDD-small) in the mirror pool.
Is there any way to do this?
 

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