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Jonathan Ellis commented on CASSANDRA-7386: ------------------------------------------- Once it's full enough then C* will start using the less-full disk since there is no room on the other. Until then, maybe the less-full disk will get balanced better out of randomness. Forcing this behavior early just turns the possibility of degraded performance later, into a certainty of degraded performance now. Am I missing something? > JBOD threshold to prevent unbalanced disk utilization > ----------------------------------------------------- > > Key: CASSANDRA-7386 > URL: https://issues.apache.org/jira/browse/CASSANDRA-7386 > Project: Cassandra > Issue Type: Improvement > Reporter: Chris Lohfink > Priority: Minor > Attachments: patch_2_1_branch_proto.diff > > > Currently the pick the disks are picked first by number of current tasks, > then by free space. This helps with performance but can lead to large > differences in utilization in some (unlikely but possible) scenarios. Ive > seen 55% to 10% and heard reports of 90% to 10% on IRC. With both LCS and > STCS (although my suspicion is that STCS makes it worse since harder to be > balanced). > I purpose the algorithm change a little to have some maximum range of > utilization where it will pick by free space over load (acknowledging it can > be slower). So if a disk A is 30% full and disk B is 5% full it will never > pick A over B until it balances out. -- This message was sent by Atlassian JIRA (v6.2#6252)