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* If you still can’t throw it away — disable all caches and pray :) the problem is that RAID controllers sometimes ignore fsync requests so Ceph can become corrupted on a sudden power loss. Even some HBAs may do that (namely some Adaptecs).

* In theory, you may try to leverage the battery- (or supercap-) backed controller cache in RAID0 mode to improve write latency. However, that can easily become shooting yourself. At least conduct some power-unplug tests if you do that.

* IOPS difference between RAID and HBA/SATA may be very noticeable. A bad or old RAID controller can easily become a bottleneck.

* HBAs also have IOPS limits. For example, it’s ~280000 iops for all disks for the LSI 9211-8i.