[jira] [Created] (MESOS-7420) Mesos slaves do not account for root disk reservation when measuring disk resources

["Adam Novak (JIRA)" <ji...@apache.org>]

Adam Novak created MESOS-7420:
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             Summary: Mesos slaves do not account for root disk reservation when measuring disk resources
                 Key: MESOS-7420
                 URL: https://issues.apache.org/jira/browse/MESOS-7420
             Project: Mesos
          Issue Type: Bug
          Components: allocation
    Affects Versions: 0.23.0
            Reporter: Adam Novak
            Priority: Minor


The Mesos slaves measure the free disk space in their work directories, and offer all of it.

Since the Mesos slaves run as root (in order to switch to the actual user any given task needs to run as), they see all unused space on a given disk as free, including space reserved for root (which is, by default, 5% of any disk).

But when the actual code that does work starts up, it probably isn't running as root, so it will only see the unreserved free space as actually free. This is in general about 5% less.

When running with disks that are nearly full, or if the scheduled user code double-checks that it actually got all the free space it asked for, this can create problems.

Mesos should not include disk space reserved for root in its offers, unless it knows that the framework it is making the offer to is going to be running its tasks as root.



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