[KUDU-605] Implement block placement hints

• Type: Sub-task
• Status: Open
• Priority: Trivial
• Resolution: Unresolved
• Affects Version/s: M5
• Component/s: fs
• Assignee: Unassigned
• Reporter: Adar Dembo
• Created: 02/Feb/15 16:46
• Updated: 29/May/20 19:37

Description

The block managers need an API that lets users choose where blocks are placed. Different block managers support different levels of granularity (e.g. locality in the log block manager can refer to disks or containers), and so we need to find a way to abstractly describe this stuff.

Some sample hints:

1. As close as possible to block X
2. As close as possible to <some opaque string>
3. On disk A
4. On disk A, B, or C
5. On any disk
6. Some combination of 1-2 and 3-5 (i.e. block locality + disk locality)

Issue Links

• relates to: KUDU-616 Mitigate tablet damage when disks are lost
• relates to: KUDU-874 Consider using the concept of DIRECTORY as Spanner does