Re: RAID Questions (fwd)

A helpful person just sent this to me. Thought some of you might be
interested. (Hope said person doesn't mind me forwarding to the list)

As you can see, it pretty much confirms my hypothesis of fairly evenly
distributed I/O.

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I haven't had a chance to do a with vs without RAID comparison, I just run
without; 6 x 4.2Gb Fast/Wide SCSI 7200rpm Seagate Barracudas on their own
Fast/Wide SCSI adapter.

As for balanced I/O, here are some (just taken) "iostat -x 5 11" stats for
the cache drives in this box; I dropped the first sample (accumulated,
not accurate for live stats). "cachemgr.cgi" says the machine is handling
over 60,000 requests per hour:

                                 extended disk statistics
disk r/s w/s Kr/s Kw/s wait actv svc_t %w %b
sd2 4.4 0.6 20.6 4.8 0.0 0.1 10.8 0 5
sd3 6.8 1.4 28.8 8.6 0.0 0.1 16.0 0 8
sd4 6.4 1.4 32.2 10.2 0.0 0.1 12.1 0 7
sd5 4.6 1.0 21.0 11.2 0.0 0.1 10.3 0 5
sd7 4.6 0.4 20.6 3.2 0.0 0.0 9.2 0 5
sd8 5.6 0.6 26.4 4.0 0.0 0.1 9.9 0 6
                                 extended disk statistics
disk r/s w/s Kr/s Kw/s wait actv svc_t %w %b
sd2 3.4 0.2 15.6 1.6 0.0 0.0 8.6 0 3
sd3 3.4 0.4 16.6 3.2 0.0 0.0 8.5 0 3
sd4 4.2 0.4 22.4 3.2 0.0 0.0 9.6 0 4
sd5 6.0 0.2 28.6 1.6 0.0 0.1 11.4 0 7
sd7 3.4 1.8 17.2 13.6 0.0 0.1 20.8 0 6
sd8 2.8 0.0 15.0 0.0 0.0 0.0 10.3 0 3
                                 extended disk statistics
disk r/s w/s Kr/s Kw/s wait actv svc_t %w %b
sd2 6.6 0.4 26.0 3.2 0.0 0.1 11.4 0 8
sd3 4.6 0.0 20.2 0.0 0.0 0.0 9.7 0 4
sd4 5.4 0.6 25.0 3.4 0.0 0.1 10.5 0 6
sd5 6.0 0.0 27.8 0.0 0.0 0.1 10.0 0 6
sd7 5.6 0.4 25.8 3.2 0.0 0.1 10.3 0 6
sd8 5.2 0.4 24.0 3.2 0.0 0.1 10.9 0 6
                                 extended disk statistics
disk r/s w/s Kr/s Kw/s wait actv svc_t %w %b
sd2 4.2 1.4 20.6 7.0 0.0 0.1 9.2 0 5
sd3 3.0 1.0 15.2 5.2 0.0 0.0 11.1 0 4
sd4 5.4 14.6 27.0 241.8 0.0 1.0 47.8 0 16
sd5 5.4 0.0 28.2 0.0 0.0 0.1 12.0 0 6
sd7 1.6 0.4 9.0 1.8 0.0 0.0 10.0 0 2
sd8 3.8 0.4 17.4 2.4 0.0 0.0 10.6 0 4
                                 extended disk statistics
disk r/s w/s Kr/s Kw/s wait actv svc_t %w %b
sd2 5.2 0.6 23.2 3.4 0.0 0.1 8.9 0 5
sd3 3.6 2.0 18.0 10.8 0.0 0.1 13.0 0 6
sd4 4.2 2.0 20.6 10.4 0.0 0.1 9.9 0 6
sd5 7.8 2.0 38.8 11.8 0.0 0.1 12.5 0 11
sd7 1.8 1.0 8.6 5.2 0.0 0.0 10.2 0 3
sd8 1.2 1.8 5.2 9.2 0.0 0.0 11.2 0 3
                                 extended disk statistics
disk r/s w/s Kr/s Kw/s wait actv svc_t %w %b
sd2 12.8 3.0 200.0 16.8 0.0 0.4 22.8 0 15
sd3 5.0 1.6 24.8 10.6 0.0 0.1 10.3 0 7
sd4 2.2 0.8 12.6 3.8 0.0 0.0 16.2 0 4
sd5 4.0 2.2 19.8 11.4 0.0 0.1 20.5 0 7
sd7 0.8 1.2 4.4 3.0 0.0 0.1 31.0 0 3
sd8 5.4 3.8 24.8 25.8 0.0 0.2 21.6 0 9
                                 extended disk statistics
disk r/s w/s Kr/s Kw/s wait actv svc_t %w %b
sd2 6.0 8.8 28.2 48.6 0.0 0.9 61.8 0 17
sd3 3.6 4.4 21.8 22.4 0.0 0.5 62.7 0 11
sd4 6.8 6.8 36.4 36.6 0.0 0.7 48.4 0 17
sd5 7.2 5.2 42.0 23.8 0.0 0.6 48.6 0 17
sd7 6.6 5.0 34.2 25.8 0.0 0.5 43.1 0 13
sd8 8.4 8.0 47.2 41.6 0.0 0.9 54.3 0 21
                                 extended disk statistics
disk r/s w/s Kr/s Kw/s wait actv svc_t %w %b
sd2 3.2 14.4 17.2 101.6 0.0 5.4 306.8 0 17
sd3 1.2 12.4 5.4 88.8 0.0 3.9 289.6 0 13
sd4 5.0 13.0 29.0 92.8 0.0 4.3 237.0 0 18
sd5 5.8 14.4 29.0 104.8 0.0 5.1 254.2 0 20
sd7 2.8 9.4 11.0 68.0 0.0 2.2 180.7 0 12
sd8 7.8 14.6 40.8 102.4 0.0 5.7 253.3 0 23
                                 extended disk statistics
disk r/s w/s Kr/s Kw/s wait actv svc_t %w %b
sd2 6.2 1.2 27.2 9.6 0.0 0.1 10.1 0 7
sd3 6.8 0.4 35.2 3.2 0.0 0.1 9.5 0 7
sd4 4.8 2.6 24.0 20.0 0.0 0.1 14.8 0 7
sd5 5.0 0.2 25.6 1.6 0.0 0.1 10.0 0 5
sd7 4.0 1.4 17.2 9.8 0.0 0.1 13.0 0 5
sd8 6.4 8.8 30.6 79.2 0.0 0.4 24.6 0 13
                                 extended disk statistics
disk r/s w/s Kr/s Kw/s wait actv svc_t %w %b
sd2 10.6 1.0 50.4 8.0 0.0 0.1 12.1 0 13
sd3 2.4 0.0 11.6 0.0 0.0 0.0 7.8 0 2
sd4 6.8 0.2 38.0 1.6 0.0 0.1 12.5 0 8
sd5 9.0 0.6 60.6 4.0 0.0 0.1 10.6 0 9
sd7 9.8 0.2 52.6 1.6 0.0 0.1 11.7 0 11
sd8 6.4 1.2 33.6 9.6 0.0 0.1 9.9 0 7
Received on Thu Apr 09 1998 - 11:46:20 MDT