Why The Disk Allocation Ratio Set to 9999 Starting From Platform9 Managed OpenStack v4.0

Problem

why the disk allocation ratio is set to 9999 in PMO v4.0 and later versions?

Environment

• Platform9 Managed OpenStack - v4.0 and Higher
• Nova-Scheduler

Answer

In PMO v3.11 we disabled DiskFilter in nova-scheduler. In the placement API introduced in PMO v4.0, there is no way to disable ram, core, and disk filters. To achieve the same functionality as earlier for disabling DiskFilter we set the disk allocation to a very high number in this case 9999.

Additional Information

If single instance disk creation requests volume size for more than the physical disk available on the host then that host will be removed using the disk filter. For more details on the allocation ratio, you can refer to this article.