MP 7,1 Monitoring specific disk i/o rates on the MP7,1

[bxs]

Subject: Monitoring specific disk i/o rates on the MP7,1

This is a FYI...

This is not specific to any Mac, but as I have had the need to monitor i/o rates recently when performing certain things on my MP7,1 I've needed to monitor certain i/o rates for specific storage devices (such as HDDs, SSDs and RAIDs). I have become accustomed to using what I believe is a unique feature to CCC (Carbon Copy Cloner) for providing and monitoring i/o rates for specific Volumes.

In CCC's lower "Volumes" sidebar one can select a Volume and a window will display and reveal the i/o read & write rates for the Volume. I find this feature invaluable at times. The Activity Monitor will provide, via its Disk tab, the overall read/write rates but they are for the overall i/o being done by all the process in the system, and not for a specific Volume of interest.

However, I've recently found this useful feature does have a minor flaw when a RAID Volume is selected.

I used CCC for monitoring a fairly large Finder copy to my RAID-0 Sonnet/Samsung card setup as 4x 1TB blades. The CCC's display for the i/o rates for the Sonnet/Samsung RAID-0 was approximately 1/4 of what I expected. After much ado, I speculated that CCC was only looking at one of the RAID-0 blades and reporting the i/o rate for it specifically, rather the the total i/o rate for the 4x 1TB blades.

I've contacted Bombitch (CCC author) about this issue and stated my speculation and it was accepted and will be something tacked onto the list of things to look at with the hope it will be addressed in a future release of CCC.

 

[bxs]

Of course, one can use iostat command in Terminal to get the data, but is not as convenient as using CCC.

Example... where disk2/4/5/6 make up the RAID-0 unit.

iostat -w 1 disk2 disk4 disk5 disk6
disk2 disk4 disk5 disk6 cpu load average
KB/t tps MB/s KB/t tps MB/s KB/t tps MB/s KB/t tps MB/s us sy id 1m 5m 15m
1004.08 51 49.91 1024.00 50 49.90 1024.00 50 49.90 1024.00 50 49.90 4 5 91 2.15 1.99 1.83
1024.00 16 15.99 1024.00 16 15.99 1024.00 16 15.99 1024.00 16 15.99 4 5 91 2.22 2.01 1.84
1010.45 75 73.76 1024.00 74 73.75 1024.00 74 73.75 1024.00 74 73.75 4 4 92 2.22 2.01 1.84
1024.00 105 104.60 1024.00 105 104.60 1024.00 105 104.60 1024.00 105 104.60 5 3 93 2.22 2.01 1.84
1014.32 105 103.61 1024.00 104 103.60 1024.00 104 103.60 1024.00 104 103.60 4 3 93 2.22 2.01 1.84
1007.61 62 60.71 1024.00 61 60.70 1024.00 61 60.70 1024.00 61 60.70 4 4 92 2.22 2.01 1.84
1024.00 24 23.89 1024.00 24 23.89 1024.00 24 23.89 1024.00 24 23.89 4 6 90 2.28 2.02 1.84
1024.00 61 60.78 1024.00 61 60.78 1024.00 61 60.78 1024.00 61 60.78 4 4 92 2.28 2.02 1.84
1014.32 105 103.92 1024.00 104 103.91 1024.00 104 103.91 1024.00 104 103.91 4 3 93 2.28 2.02 1.84
1014.23 104 102.97 1024.00 103 102.96 1024.00 103 102.96 1024.00 103 102.96 5 3 92 2.28 2.02 1.84
1024.00 65 64.72 1024.00 65 64.72 1024.00 65 64.72 1024.00 65 64.72 4 4 92 2.28 2.02 1.84
1009.69 71 69.99 1024.00 70 69.98 1024.00 70 69.98 1024.00 70 69.98 4 4 92 2.26 2.02 1.84
1024.00 65 64.84 1024.00 65 64.84 1024.00 65 64.84 1024.00 65 64.84 4 4 92 2.26 2.02 1.84
1014.14 103 101.98 1024.00 102 101.97 1024.00 102 101.97 1024.00 102 101.97 5 3 92 2.26 2.02 1.84
1024.00 102 101.92 1024.00 102 101.92 1024.00 102 101.92 1014.14 103 101.93 5 3 92 2.26 2.02 1.84
1000.30 27 26.24 1001.63 27 26.27 1002.67 27 26.30 1001.04 27 26.26 4 2 94 2.26 2.02 1.84
256.00 1 0.25 256.00 1 0.25 256.00 1 0.25 256.00 1 0.25 4 0 95 2.24 2.02 1.84
0.00 0 0.00 0.00 0 0.00 0.00 0 0.00 0.00 0 0.00 4 0 96 2.24 2.02 1.84
0.00 0 0.00 0.00 0 0.00 0.00 0 0.00 8.00 1 0.01 5 3 93 2.24 2.02 1.84
0.00 0 0.00 0.00 0 0.00 0.00 0 0.00 0.00 0 0.00 6 3 91 2.24 2.02

 

[bxs]

Well, I've ended writing myself a shell script to give me the desired total i/o rate for my Sonnet/Samsung RAID-0 device named "Swift-IO" installed in my MP7,1. The script employs the iostat command.

I pass the disk IDs that make up the RAID-0 to my script, and offer an example below... Seeing some 8,243 MB/s makes me very very happy. 👍

I executed AJA System Test and directed it at my Swift-IO device. to create writes and reads.... and the results are shown below running my shell script Swift-IO-Data-Rate

./Swift-IO-Data-Rate disk0 disk1 disk2 disk3
0 MB/s
0 MB/s
0 MB/s
0 MB/s
489.29 MB/s
5620.85 MB/s
5112.81 MB/s
6163.15 MB/s
5276.99 MB/s
6755.69 MB/s
6154.85 MB/s
7605.82 MB/s
6066.64 MB/s
5958.13 MB/s
8243.07 MB/s