lucid partitioner creates unusable disk space when creating software raid arrays

[stop]

Binary package hint: partman-base

When creating a raid array (with alternate cd or server cd) the lucid partitioner creates some small unusable disk space for each partition. I have not seen this in previous releases.
See attached screen shot for more information.

[Colin Watson (cjwatson)]

This bit should just not be displayed in the UI. I did this for ordinary disks but for some reason it isn't working properly for RAID.

[Yung-Chin Oei (yungchin)]

Just to add in case it's helpful: the same unusable entry can be seen when creating a partition in an encrypted volume. (Out of curiosity, can I ask what this space represents?)

[Tuomas Heino (iheino+ub)]

Disk space is allocated in megabyte-sized chunks for performance reasons.

That implies that there will be sub-megabyte areas of unused space between partition table and partitions and at the end of disk as well. Similar to the partition tables, raid and encryption both have metadata which imply further alignment requirements.

For whatever it is worth, I find those "unusable" things in partman to be illustrative, but yes they can be confusing for the novice user. As such, we could consider showing them only when the installer was started in "expert mode".

<offtopic extension="note">
Would (even single-disk) partitionable raid1 by default make sense? I find such rather useful for VMs that can be booted both on bare HW and in VM, since raid1->gpt->data (inside VM) is about as easy for the bootloaders as gpt->raid1->gpt->data (on bare HW).
</offtopic>