cassandra-commits mailing list archives

Site index · List index
Message view « Date » · « Thread »
Top « Date » · « Thread »
From "Yuki Morishita (JIRA)" <>
Subject [jira] [Commented] (CASSANDRA-7386) JBOD threshold to prevent unbalanced disk utilization
Date Wed, 19 Nov 2014 18:59:35 GMT


Yuki Morishita commented on CASSANDRA-7386:

LGTM, except in the test code:

// at least (rule of thumb) 100 iterations
if (i >= 100)
// random weighted writeable directory algorithm fails to return all possible directories
// many tries
if (i >= 10000000)

I think you mean to check the second `if` first?

> JBOD threshold to prevent unbalanced disk utilization
> -----------------------------------------------------
>                 Key: CASSANDRA-7386
>                 URL:
>             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

View raw message