There once was a bug in an earlier kernel, in which the min_speed is what
the rebuild ran at if you had a specific chunk size, have you tried to
echo 30000 > to min_speed? Does it increase it to 30mb/s for the rebuild?
On Mon, 28 Jul 2008, Jon Nelson wrote:
Some more data points, observations, and questions.
For each test, I'd --create the array, drop the caches, --grow, and
then watch vmstat and also record the time between
kernel: md: resuming resync of md99 from checkpoint.
and
kernel: md: md99: resync done.
I found two things:
1. metadata version matters. Why?
2. VERY LITTLE I/O takes place (between 0 and 100KB/s, typically no
I/O at all) according to vmstat. Why? If it takes 1m34s to "grow" the
array, but no I/O is taking place, then what is actually taking so
long?
3. I removed the bitmap for these tests. Having a bitmap meant that
the overall speed was REALLY HORRIBLE.
The results:
metadata: time taken
0.9: 27s
1.0: 27s
1.1: 37s
1.2: 1m34s
Questions (repeated):
1. Why does the metadata version matter so much?
2. If no I/O is taking place, why does it take so long? [ NOTE: I/O
must be taking place but why doesn't vmstat show it? ]
--
Jon
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