Some PERC H730P rebuild performance numbers

Little while back I rebuilt my RAID array (went from RAID10 to RAID6 because I needed more capacity) and couldn’t find any information online about what the actual performance hit is to the array when a background initialization is happening.

The Dell software says there is a minor performance impact during the operation and you can still use your system as per-usual. I was curious though, how much of an impact was there? I ran some CrystalDiskMarks during and after the process for fun.

The disks I am using are 10TB Seagate Ironwolfs (7200RPM, CMR)

Here are my PERC Controllers settings:

Here is the CrystalDiskMark info during the background initialization with the following test settings:

Test Count: 5
Test Size 1GiB (PERC has a 2GB cache so it was likely in play during these)

	Read during (MB/s)	Read after (MB/s)	% Improvement	Write during (MB/sec)	Write after (MB/sec)	% Improvement	Read during (IOPS)	Read after (IOPS)	% Improvement	Write during (IOPS)	Write after (IOPS)	% Improvement
QEC1M Q8T1	1082.30	1379.37	27.45	938.86	1067.59	13.71	1032.16	1315.47	27.45	895.37	1018.13	13.71
SEQ1M Q1T1	669.67	1157.87	72.90	906.00	947.21	4.55	638.65	1104.23	72.90	864.03	903.33	4.55
RND4K Q32T1	69.65	64.82	-6.93	65.98	53.76	-18.52	17005.37	15825.93	-6.94	16108.15	13124.27	-18.52
RND4K Q1T1	6.84	30.04	339.18	28.76	44.43	54.49	1668.95	7333.98	339.44	7021.73	10846.44	54.47
Average			108.15			13.56			108.21			13.55

Test Count: 5
Test Size 8GiB (these numbers should better reflect the actual disk performance)

	Read during (MB/s)	Read after (MB/s)	% Improvement	Write during (MB/sec)	Write after (MB/sec)	% Improvement	Read during (IOPS)	Read after (IOPS)	% Improvement	Write during (IOPS)	Write after (IOPS)	% Improvement
QEC1M Q8T1	857.75	988.56	15.25	876.61	908.28	3.61	818.02	942.79	15.25	836.03	866.20	3.61
SEQ1M Q1T1	522.62	940.35	79.93	846.92	911.23	7.59	527.02	896.79	70.16	807.69	869.02	7.59
RND4K Q32T1	10.94	13.38	22.30	19.87	20.04	0.86	2670.90	3267.33	22.33	4851.07	4893.31	0.87
RND4K Q1T1	1.13	1.43	26.55	12.86	14.80	15.09	274.90	350.10	27.36	3139.65	3613.53	15.09
Average			36.01			6.79			33.78			6.79

Bottom line, looks like there is roughly a 30% performance hit while a background initialization is running which is pretty close to the configured rates on the PERC controller.