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From "Tim Bain (JIRA)" <>
Subject [jira] [Commented] (AMQ-6441) Incorrect File System Size Reported with Amazon Elastic File System (EFS)
Date Thu, 29 Sep 2016 12:49:20 GMT


Tim Bain commented on AMQ-6441:

This approach addresses the immediate problem, with an 8 EB volume.  It will do nothing for
a 16EB volume, a 32 EB volume, or any other multiple of 16 EB, because those volumes will
all show as small positively-sized volumes.  (If 8EB is 4193 bytes over half the range of
a long, double that - 16 EB - will be 4193 * 2 = 8386 bytes over the full range of a long,
and will mod down to the small but positive remainder: 8386 bytes.  And multiplying that number
by anything will result in a volume that is 8386 bytes times the multiplier, which will probably
be smaller than the KahaDB store.)  So the proposed (and implemented) algorithm fixes today's
problem, but does nothing for the next problem.

The only safe way to allow people to not be bit by this in the future is to implement the
flag.  It would be defaulted to false, and enabled only when they deem it necessary based
on their own knowledge of their storage situation.  People don't go changing values randomly,
so no one's going to make the change unless they believe they need it, and if they know about
the setting to misconfigure it, they'll know what to set back when it causes them problems.

Based on the above, I recommend rejecting the pull request that was just made, and reworking
the change to include a flag.  Otherwise, we're going to get to do this all over again whenever
Amazon increases the default EFS volume size to 16EB.

> Incorrect File System Size Reported with Amazon Elastic File System (EFS)
> -------------------------------------------------------------------------
>                 Key: AMQ-6441
>                 URL:
>             Project: ActiveMQ
>          Issue Type: Bug
>    Affects Versions: 5.11.1
>            Reporter: Ismail Bhana
> I've set up Active MQ in production with a shared file system master/slave configuration
(KahaDB). I've set everything up and mounted the EFS on both EC2 instances. 
> When I check the disk free stats I get 8 exabytes for the shared file system: 
> {code}
> $ df -h 
> eu-west-1a.***  8.0E     0  8.0E   0% /mnt/efs 
> {code}
> Unfortunately, ActiveMQ cannot interpret this number (8 exabytes). This may be due to
integer truncation.
> Here is a snippet of the log:
> {code}
> Store limit is 102400 mb (current store usage is 0 mb). The data directory: /mnt/efs/kahadb
only has -8796093022208 mb of usable space - resetting to maximum available disk space: -8796093022207
> Store limit is -8796093022207 mb, whilst the max journal file size for the store is:
32 mb, the store will not accept any data when used. 
> {code}

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