On Sun, 10 Jun 2012, Robert Huff wrote:
Ronald F. Guilmette writes:
Warren? Just a couple more quick questions. You recommend:
>> dump -C16 -b64 -0uanL -h0 -f - /usr | (cd /mnt && restore -ruf -)
I'm real curious about you suggestions for the -C and -b values.
I have what amounts to a personal workstation. Yea, OK, it is running
mail, web, and FTP servers also, but fundementailly, it is not that busy
most of the time. And it's got 4GB of main installed. On average, I
suspect that I ain't even using half of that.
Given all that, why shouldn't I specify (e.g.): -C512 -b1024 ?
Wouldn't that all make the dump go faster?
There are many possible obstacles to faster dump speed;
enumerating them is left as an exercise for the reader.
As it happens, I have a set-up very similar to what you
describe ... except with 8g of memory. A few years ago I did some
testing with various cache sizes (as part of diagnosing other
problems) and ended up with C=32.
(I should probably run the tests again, given some hardware
changes since.)
That machine's level 0 runs tonight; I will try to remember to
(retain and) post the results.
-C16 is a little small because it's hard to tell how much memory someone
running the example will have. I usually use -C32 on machines with
plenty of memory. Remember that dump forks multiple times, so it's not
32M, but N*32M.
-b64 is the largest safe buffer size to use. People have experienced
problems with larger amounts.
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