Making a bootable backup (hard)disk... how?
wblock at wonkity.com
Mon Jun 11 00:36:33 UTC 2012
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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