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Performance benchmarking shows that skipping the raw format blockdev improves I/O performance. On an Optane NVMe drive where small improvements are most noticeable it reduces I/O latency by ~300 ns and increases IOPS by 3,000.

The raw format driver simply passes requests to the protocol driver (raw-posix, iscsi, etc). Omitting it does not affect disk I/O except that it increases performance slightly.

Note that the raw format driver can be used to expose a subset of the underlying storage using the offset=/size= parameters. In this case the raw format driver is necessary and cannot be omitted.

Please omit the raw format blockdev when possible.

The raw driver was added for symmetry with what qemu did with -drive. Some tweaking will be required though as the block job code expects the 'format' layer to be always present.

After evaluating this issue, there are no plans to address it further or fix it in an upcoming release.  Therefore, it is being closed.  If plans change such that this issue will be fixed in an upcoming release, then the bug can be reopened.

This is still an ongoing effort.

Issue migration from Bugzilla to Jira is in process at this time. This will be the last message in Jira copied from the Bugzilla bug.