Creating a partition or a Volume Group on the whole disk leaves free space.

Bug #1509535 reported by Andres Rodriguez on 2015-10-23
This bug affects 1 person
Affects Status Importance Assigned to Milestone
Jeffrey C Jones

Bug Description

When creating LVM in the WebUI, it does not take the whole disk:

Related branches

Changed in maas:
milestone: none → 1.9.0
importance: Undecided → High
status: New → Triaged
summary: - LVM creation does not take the whole disk
+ Creating a partition or a Volume Group on the whole disk leaves free
+ space.
Changed in maas:
importance: High → Critical
Changed in maas:
assignee: nobody → Jeffrey C Jones (trapnine)
status: Triaged → In Progress
Jeffrey C Jones (trapnine) wrote :

This is a design / form units / GIGO issue.
The creation UI is working correctly, but not very helpfully.
Basically we need more sig figs or to also show/input the sizes in MB or bytes.

Details: The UI shows the device having 128.0 GB of available space, and pre-fills 128.0GB on partition creation. But the device actually has 128.035676160 GB free, leaving leaving the 0.03+GB (~31 MB) free after the precisely sized 128.000 GB partition is created.

So it boils down to two problems:
- you're shown a rounded large-unit value for available size, hiding actual size
- you're pre-filled the same rounded large-value unit in the form, hiding error

MB, GB and TB are selectable on the input form, so one could specify in MB, which is probably close enough. But the user can't see how many MB (or bytes) are free so wouldn't know what to provide.

We need to make a decision here about units. Two options come to mind:

1) - display the sizes in MB or bytes (with humanized values still shown for convenience)
   - allow and pre-fill input on the form in MB or bytes

2) Show and/or pre-fill with enough sig figs to provide MB accuracy - like 128.035 GB or 2.000005 TB

Hard to decide which way is more annoying to the end user.

Jeffrey C Jones (trapnine) wrote :

After discussing we're going with Option 3: recognize when the user accepts the prefilled default size and interpret that as 'use the whole disk'.

Other options were:
- add a "use whole disk" checkbox, checked by default, that disables size input
- add a "percentage of disk" input field, defaulted to 100% (changing either field would update the other)

Changed in maas:
status: In Progress → Fix Committed
Changed in maas:
status: Fix Committed → Fix Released
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