Slow sequential speeds on 9x7-drive raidz2 (ZFS ZoL 0.8.1)

Solution 1:

Good question.

• I think your sparse zvol block size should be 128k.
• Your ZIO scheduler settings should all be higher, like minimum 10 and max 64.
• zfs_txg_timeout should be much longer. I do 15 or 30s on my systems.
• I think the multiple RAIDZ3's (or was that a typo) are overkill and play a big part in the performance. Can you benchmark with RAIDZ2?

Edit: Install Netdata on the system and monitor utilization and ZFS stats.

Edit2: This is for a Veeam repository. Veeam support Linux as a target, and works wonderfully with ZFS. Would you consider benchmarking that with your data? zvols aren't an ideal use case for what you're doing, unless the NIC's offload is a critical part of the solution.