[ppml] HD Ratio changes

[Owen DeLong]

OK... I took your mail, and tried to make this simple...

I wrote the the attached PERL script to compute the number of hosts needed 
for
a .996 HD ratio and the number of hosts needed for 80% utilization and came
up with the following table.  Either HD doesn't do what you claim, or, it
isn't simple enough for me and my math didn't work right.  The table here
shows that in all cases, a .996 HD ratio is a larger number than the
80% requirement, and, that the more space you have, the worse it gets.  I'm
guessing I've got an error in my code, but, this is as easy as I thought it
could be to compute the HD ratio needed for a given block size.  If you have
an easier way, please post code.


+--------+-----------+-----------+-----------+---------------+
| Prefix |  N Hosts  |  .996 HD  |   80% HD  | .996 HD - 80% |
+--------+-----------+-----------+-----------+---------------+
|     /3 | 536870912 | 495393603 | 429496729 |      65896873 |
|     /4 | 268435456 | 248384517 | 214748364 |      33636152 |
|     /5 | 134217728 | 124537069 | 107374182 |      17162886 |
|     /6 |  67108864 |  62441419 |  53687091 |       8754327 |
|     /7 |  33554432 |  31307393 |  26843545 |       4463847 |
|     /8 |  16777216 |  15697157 |  13421772 |       2275384 |
|     /9 |   8388608 |   7870369 |   6710886 |       1159482 |
|    /10 |   4194304 |   3946111 |   3355443 |        590667 |
|    /11 |   2097152 |   1978533 |   1677721 |        300811 |
|    /12 |   1048576 |    992013 |    838860 |        153152 |
|    /13 |    524288 |    497383 |    419430 |         77952 |
|    /14 |    262144 |    249383 |    209715 |         39667 |
|    /15 |    131072 |    125037 |    104857 |         20179 |
|    /16 |     65536 |     62693 |     52428 |         10264 |
|    /17 |     32768 |     31433 |     26214 |          5218 |
|    /18 |     16384 |     15761 |     13107 |          2653 |
|    /19 |      8192 |      7901 |      6553 |          1347 |
|    /20 |      4096 |      3961 |      3276 |           684 |
|    /21 |      2048 |      1987 |      1638 |           348 |
|    /22 |      1024 |       995 |       819 |           175 |
|    /23 |       512 |       499 |       409 |            89 |
|    /24 |       256 |       251 |       204 |            46 |
|    /25 |       128 |       125 |       102 |            22 |
|    /26 |        64 |        63 |        51 |            11 |
|    /27 |        32 |        31 |        25 |             5 |
|    /28 |        16 |        15 |        12 |             2 |
|    /29 |         8 |         7 |         6 |             0 |
|    /30 |         4 |         3 |         3 |             0 |
|    /31 |         2 |         1 |         1 |             0 |
+--------+-----------+-----------+-----------+---------------+
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