[ale] Performance issue

[Jim Kinney]

Getting DISMAL performance from new hardware.

Twin 6-core Xeon E5-2630L v.2 @2.40 GHz
128GB DDR4 RAM
LSI megaraid 2108 in a PCIe v3 slot
Onboard LSI 3108
Drives are all 6Gbps SAS2 4TB
2 arrays, RAID 6, one is 40Tb, other 104TB

Everything hardware says I should expect a minimum throughput of 12Gbps on
either array.

The max I'm getting from iotop is 784 Mbps.

W. T. F!!!

According to top, the system is basically idle. Ditto from iostat and every
other tool I check. I'm doing a 'cp -a' from/to same array.

Yes. New location is Luks encrypted. That process is totally asleep it's
getting so little work. The rng is busy (dev/random is not running out
(watch -n 1 cat /proc/sys/kernel/random/entropy_avail was always above
2048)) but not overloaded or asleep.

Tested going unencrypted to unencrypted with similar performance.

Changed tuned-adm to latency-performance from balanced and the read portion
of the cp went to 0 bps for 20 seconds until I switched it back to balanced
mode. So that was a fail. It improved greatly using throughout-performance
mode (bursts of 250MB/s) but was still showing long periods of 0 writes.
Load went up from a paltry 8 to 22 so it's working more.

But top shows wa values across multiple cores hitting 100 so it's hitting a
wall somewhere.

Any ideas of more places to look?
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