Evening All, I’ve been testing the RBD snapshot functionality and one thing that I have seen is that once you take a snapshot of a RBD and perform small random IO on the original RBD, performance is really bad due to the amount of write amplification going on doing the COW’s. ie every IO to the parent no matter what size, equals 12MB of writes. I was wondering if there was anyway to redirect these writes to a different pool. Since only a small capacity would be required, a SSD/NVME pool could be provisioned very cheaply and would hopefully provide enough performance to allow the IO operations to the parent to be unaffected. I’ve looked at the RBD layering, which sort of looks like you can do stuff like this and also change the order. But it looks like you have to base it on an existent snapshot, so I believe I would still have the same problem. Or is there a “hidden feature” to make normal snapshots use this layering functionality? Nick |
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