Hi! This is basically right, but: 1. How do you know the 3TB storage will be 3TB on cassandra? This depends how the data is serialized, compressed and how often it changes and it depends on your compaction settings 2. 50% free space on STCS is only required if you do a full compaction of a single CF that takes all the space. Normally you need as much free space as the target SSTable of a compaction will take. If you split your data across more CFs, its unlikely you really hit this value.
.. probably you should do some tests. But in the end it is always good to have some headroom. I personally would scale out if free space is < 30% but that always depends on your model. 2017-01-26 9:56 GMT+01:00 Raphael Vogel <raphael.vo...@web.de>: > Hi > Just want to validate my estimation for a C* cluster which should have > around 3 TB of usable storage. > Assuming a RF of 3 and SizeTiered Compaction Strategy. > Is it correct, that SizeTiered Compaction Strategy needs (in the worst > case) 50% free disc space during compaction? > > So this would then result in a cluster of 3TB x 3 x 2 == 18 TB of raw > storage? > > Thanks and Regards > Raphael Vogel > -- Benjamin Roth Prokurist Jaumo GmbH · www.jaumo.com Wehrstraße 46 · 73035 Göppingen · Germany Phone +49 7161 304880-6 · Fax +49 7161 304880-1 AG Ulm · HRB 731058 · Managing Director: Jens Kammerer
