Hi Dan,

Thank you for your answer. Yes, I understood, that I need to have the initial 
crush weight 0. That's how I tested when manually adding OSDs in my test 
cluster. I see that with the settings mentioned by you adding OSDs using the 
ceph-disk tool will also have the crush weight 0, so I could use it with chef 
cookbook. Thank you!!!

Kind regards,

On 04.08.2017 10:58, Dan van der Ster wrote:
Hi Laszlo,

The script defaults are what we used to do a large intervention (the
default delta weight is 0.01). For our clusters going any faster
becomes disruptive, but this really depends on your cluster size and

BTW, in case it wasn't clear, to use this script for adding capacity
you need to create the new OSDs to your cluster with initial crush
weight = 0.0

osd crush initial weight = 0
osd crush update on start = true

-- Dan

On Thu, Aug 3, 2017 at 8:12 PM, Laszlo Budai <las...@componentsoft.eu> wrote:
Dear all,

I need to expand a ceph cluster with minimal impact. Reading previous
threads on this topic from the list I've found the ceph-gentle-reweight
created by Dan van der Ster (Thank you Dan for sharing the script with us!).

I've done some experiments, and it looks promising, but it is needed to
properly set the parameters. Did any of you tested this script before? what
is the recommended delta_weight to be used? From the default parameters of
the script I can see that the default delta weight is .5% of the target
weight that means 200 reweighting cycles. I have experimented with a
reweight ratio of 5% while running a fio test on a client. The results were
OK (I mean no slow requests), but my  test cluster was a very small one.

If any of you has done some larger experiments with this script I would be
really interested to read about your results.

Thank you!
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