On Thu, May 4, 2017 at 5:30 AM Loic Dachary <loic@xxxxxxxxxxx> wrote:
Hi,
In a cluster where the failure domain is the host and dozens of hosts, the 85% default for nearfull ratio is fine. A host failing won't suddenly make the cluster 99% full. In smaller clusters, with 10 hosts or less, it is likely to not be enough. And in larger clusters 85% may be too much to reserve and 90% could be more than enough.
Is there a way to calculate the optimum nearfull ratio for a given crushmap ?
Is failure recovery the primary concern with the nearfull flag? Best I can recall it was initially more about the CRUSH placement imbalance and preventing any one OSD from going actually full and halting the whole cluster.
-Greg
Cheers
--
Loïc Dachary, Artisan Logiciel Libre
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