scheduler: disk_filter permits scheduling on full drives

Bug #1513654 reported by Andrew Bogott on 2015-11-05
This bug affects 1 person
Affects Status Importance Assigned to Milestone
OpenStack Compute (nova)
John Garbutt

Bug Description

I use qcow images and have disk_allocation_ratio == 2.1 to allow large amounts of overcommitting of disk space. To quote the nova config reference:

> If the value is set to >1, we recommend keeping track of the free disk space, as the value approaching 0 may result in the incorrect
> functioning of instances using it at the moment.

Good advice, but 'keeping track' can be a bit impractical at times. I just now had the scheduler drop a large sized instance onto a server with a 98% full drive since the behavior of disk_allocation_ratio intentionally ignores the actual free space on the drive.

I propose that we add an additional config setting to the disk scheduler so that I can overschedule but can /also/ request that the scheduler stop piling things onto an already groaning server.

Fix proposed to branch: master

Changed in nova:
status: New → In Progress
Changed in nova:
importance: Undecided → Low
tags: added: scheduler
Changed in nova:
importance: Low → Wishlist
Changed in nova:
assignee: nobody → Andrew Bogott (andrewbogott)

Fix proposed to branch: master

Changed in nova:
assignee: Andrew Bogott (andrewbogott) → John Garbutt (johngarbutt)

Submitter: Jenkins
Branch: master

commit 13c1301f41edee6559220f2dfa92211714925f8d
Author: andrewbogott <email address hidden>
Date: Mon Dec 21 22:04:40 2015 -0600

    Add a disk space weight-based scheduler.

    By default this is turned on and has equal weight to the
    ram weigher.

    DocImpact: Added the disk_weight_multiplier config option
    Closes-Bug: 1513654
    Change-Id: I29ce73122ad1860081b64b75646a297dfbb8d292

Changed in nova:
status: In Progress → Fix Released

This issue was fixed in the openstack/nova development milestone.

Change abandoned by Stephen Finucane (<email address hidden>) on branch: master

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