On 04/07/2009, at 2:08 PM, Miles Nordin wrote:
iostat -xcnXTdz c3t31d0 1
on that device being used as a slog, a higher range of output looks
like:
extended device statistics
r/s w/s kr/s kw/s wait actv wsvc_t asvc_t %w %b device
0.0 1477.8 0.0 2955.4 0.0 0.0 0.0 0.0 0 5 c7t2d0
Saturday, July 4, 2009 2:18:48 PM EST
cpu
us sy wt id
0 1 0 99
I started a second task from the first server while using only a
single slog and the performance of the SSD got up to 1900 w/s
extended device statistics
r/s w/s kr/s kw/s wait actv wsvc_t asvc_t %w %b device
0.0 1945.8 0.0 3891.7 0.0 0.1 0.0 0.0 0 6 c7t2d0
0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0 0 c7t3d0
Saturday, July 4, 2009 2:23:11 PM EST
cpu
us sy wt id
0 1 0 99
Interestingly, adding a second SSD into the mix and a 3rd writer (on a
second client system) showed no further increases:
extended device statistics
r/s w/s kr/s kw/s wait actv wsvc_t asvc_t %w %b device
0.0 942.3 0.0 1884.4 0.0 0.0 0.0 0.0 0 3 c7t2d0
0.0 942.4 0.0 1884.4 0.0 0.0 0.0 0.0 0 3 c7t3d0
Add the ramdisk as a 3rd slog with 3 writers and only an increase in
the speed of the slowest device
extended device statistics
r/s w/s kr/s kw/s wait actv wsvc_t asvc_t %w %b device
0.0 453.6 0.0 1814.4 0.0 0.0 0.0 0.0 0 1 ramdisk1
0.0 907.2 0.0 1814.4 0.0 0.0 0.0 0.0 0 3 c7t2d0
0.0 907.2 0.0 1814.4 0.0 0.0 0.0 0.0 0 3 c7t3d0
Saturday, July 4, 2009 2:29:08 PM EST
cpu
us sy wt id
0 2 0 98
When only the ramdisk is used as a slog, it gives the following results:
extended device statistics
r/s w/s kr/s kw/s wait actv wsvc_t asvc_t %w %b device
0.0 3999.4 0.0 15997.8 0.0 0.0 0.0 0.0 0 2 ramdisk1
Saturday, July 4, 2009 2:36:58 PM EST
cpu
us sy wt id
0 3 0 96
Any insightful observations?
cheers,
James
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