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Yuki Morishita commented on CASSANDRA-7386: ------------------------------------------- LGTM, except in the test code: {code} // at least (rule of thumb) 100 iterations if (i >= 100) break; // random weighted writeable directory algorithm fails to return all possible directories after // many tries if (i >= 10000000) fail(); {code} I think you mean to check the second `if` first? > JBOD threshold to prevent unbalanced disk utilization > ----------------------------------------------------- > > Key: CASSANDRA-7386 > URL: https://issues.apache.org/jira/browse/CASSANDRA-7386 > Project: Cassandra > Issue Type: Improvement > Components: Core > Reporter: Chris Lohfink > Assignee: Robert Stupp > Priority: Minor > Fix For: 2.1.3 > > Attachments: 7386-2.0-v3.txt, 7386-2.0-v4.txt, 7386-2.1-v3.txt, > 7386-2.1-v4.txt, 7386-v1.patch, 7386v2.diff, Mappe1.ods, > mean-writevalue-7disks.png, patch_2_1_branch_proto.diff, > sstable-count-second-run.png, test1_no_patch.jpg, test1_with_patch.jpg, > test2_no_patch.jpg, test2_with_patch.jpg, test3_no_patch.jpg, > test3_with_patch.jpg > > > 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 (v6.3.4#6332)