On 8/30/19 5:01 PM, 74cmo...@gmail.com wrote:
Hi,
after adding an OSD to Ceph it is adviseable to create a relevant entry in Crush map using a weight size depending on disk size.

Example:
ceph osd crush set osd.<id> <weight> root=default host=<hostname>

Question:
How is the weight defined depending on disk size?
Which algorithm can be used to calculate the weight?

From my first Ceph installation (luminous) the Crush map entry for
- HDD device with 1.80TB size (output of lsscsi -s): weight was 1.627229
- NVMI device with 3.20TB size (output of lsscsi -s): weight was 2.910889


Actually you can define "human readable" value. HDD 1.80TB is a 2TB for human. So you can declare this weight as "2.0".



k
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