Microceph and Openstack Question

Support and Help
1

I tried hard to find information on this but on my nodes for openstack I have mixtures of different storage types (HDD, SATA SSD and NVME SSD) can they pool separate as i feel lumping them as 1 pool would cause issues as different speeds. Or how does it work?

2

Ceph (and MicroCeph) can handle mixed storage types, but you should not put HDD, SATA SSD, and NVMe in the same pool. A pool will effectively perform at the level of the slowest disks, so mixing speeds will cause performance and latency issues.

The recommended approach is to separate them into different pools, using Ceph device classes (hdd, ssd, nvme) and appropriate CRUSH rules. This is fully supported in MicroCeph.

When integrated with OpenStack, you can then map each pool to a different Cinder volume type, allowing workloads to explicitly choose the appropriate storage tier (HDD for cold data, SSD/NVMe for high-IOPS workloads).

In short: mixed disks are fine, mixed pools are not — separate pools per storage class is the documented and recommended design.

3

Ok which i expected that, I am trying to find docs to do the separate pools and thats where I’m hitting a snag. I definitely want each pool to have its correct type.

Also does it matter sizes or is it more just maintain the proper storage medium?

4

You should create separate pools per storage class (HDD / SSD / NVMe).

  1. Tag OSDs with device classes (ceph osd crush set-device-class ...).
  2. Create CRUSH rules that place data only on those classes.
  3. Create pools and set their crush_rule to the appropriate class.
    This way you avoid slow devices “choking” fast ones; then map each pool to an OpenStack volume type (Cinder) so workloads select the correct tier. See Ceph docs on device classes, CRUSH rules and RBD/OpenStack for examples.

https://www.ibm.com/docs/en/storage-ceph/7.1.0?topic=overview-crush-storage-strategies-examples

5

Oooh I see you can use the normal ceph tooling for some components! Ok thats makes more sense why it seem the microceph command was not as feature packed.

6

This topic was automatically closed 24 hours after the last reply. New replies are no longer allowed.