I just read that message from James Manning on some performance tuning, and
it made me think about this. On some of our RAID controllers, they collect
statistics for the RAID volumes. The one that I'm thinking of collects
things like this, except that I've trimmed some of the irrelevant
information.
Reads Writes
1 KB 26537 190557
2 KB 16084 56161
4 KB 118645 756926
8 KB 61132 110969
16 KB 75669 34512
32 KB 132924 4567
64 KB 324735 10850
128 KB 0 0
256 KB 0 0
512 KB 0 0
1 MB+ 0 0
Total 755726 1164542
The statistics report a few other things, but from looking at numbers like
these, I could grab them into a spreadsheet program like Gnumeric,
manipulate them a bit, and figure out what the "optimal" sizes for things on
my RAID array are.
Is there any chance of keeping track of these with software RAID? Somewhere
like /proc/mdinfo/ or even another mdSTUFF file in or, or possibly just
tacked onto the end of the mdstat that's there already. Now, I can see
somebody asking about performance considerations here, but it's storing a
tiny amount of data, just the number of reads and writes for each size block
of data. Does this sound like something that would be useful? Can I pay
somebody to write it? :-) Thanks,
Grego
