Thread (24 messages) 24 messages, 5 authors, 2007-06-26

Re: stripe_cache_size and performance

From: Justin Piszcz <hidden>
Date: 2007-06-26 14:37:06


On Tue, 26 Jun 2007, Jon Nelson wrote:
On Tue, 26 Jun 2007, Justin Piszcz wrote:
quoted

On Tue, 26 Jun 2007, Jon Nelson wrote:
quoted
On Mon, 25 Jun 2007, Justin Piszcz wrote:
quoted
Neil has a patch for the bad speed.
What does the patch do?
quoted
In the mean time, do this (or better to set it to 30, for instance):

# Set minimum and maximum raid rebuild speed to 60MB/s.
echo "Setting minimum and maximum resync speed to 60 MiB/s..."
echo 60000 > /sys/block/md0/md/sync_speed_min
echo 60000 > /sys/block/md0/md/sync_speed_max
sync_speed_max defaults to 200000 on this box already.
I tried a binary search of values between the default (1000)
and 60000 which resulted in some pretty weird behavior:

at values below 26000 the rate (also confirmed via dstat output) stayed
low.  2-3MB/s.  At 26000 and up, the value jumped more or less instantly
to 70-74MB/s. What makes 26000 special? If I set the value to 20000 why
do I still get 2-3MB/s actual?
quoted
You want to use sync_speed_min.
I forgot to say I changed the values of sync_speed_min.


--
Jon Nelson [off-list ref]
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Sounds quite strange, what chunk size are you using for your RAID?
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