Status update on the effort to fix the Cinder Quota system. Cover the effort done up till now, performance results, deployment poll results, and next steps.

1. Fixing Cinder Quotas
UPDATE

2. Pain point
Quotas?
What’s that?
These are not the
quotas you are
looking for
'Tis but a scratch I’ve had worse Just a flesh wound!

3. Now: Reservations
Extend existing volume of type LVM by 100GB
✔
in-
use
limit
8
1100
10
volume
s
gigabytes 910
7
10
volumes_lv
m
1100
gigabytes_lvm 905
reserve
d
1
100
1
100
✘
✘
✔
request
0
100
0
100
+
≥
+
≥
+
≥
+
≥
+
+
+
+

4. Proposal
● Remove reservation accounting
● Dynamically count resources
● Ensure necessary indexes

5. Performance

6. Not a simple query
● Limits calculated from 2 tables:
○ Global defaults: quotaclasses
○ Project specific: quotas
● Limits by volume type: No direct cross
○ Limits by type name
○ Volumes by type id
● Snapshot GBs may count towards volume GBs
○ Also by volume type
● Still need reservations table: eg. extend

7. Performance
● Look at 2 operations:
○ Create volume
○ Get current usage
● Concurrency
○ Single request
○ Multiple requests (10)
● Things to look at:
○ Time: Per request avg & total
○ CPU: Total and per service (DB/Cinder)

8. Create with concurrency = 1

9. Create with concurrency = 10

10. Get usage with concurrency = 1

11. Get usage with concurrency = 10

12. Survey
Largest project Typical project
Volumes Snapshots Backups Volumes Snapshots Backups
1 70000 30000 0 10000 5000 0
2 3300 41 490 17 7 36
3 2500 0 0 1800 0 0
4 2000 2000 50 5 2 1
5 568 5 0 20 1 0
6 250 20 100 20 50
7 200 400 200 120 240 120
8 100 0 0 50 0 0
9 20 10 20 10 5 10
10 10 2 1 2 0 0

13. What to do?

14. Option 1
● Move forward
○ New counting driver is the default
○ Most projects will be better:
■ Faster
■ More accurate
○ Tell large projects:
It’s a tradeoff, accuracy for speed

15. Option 2
● Mixed solution:
○ Same as old: Use quota_usages table
○ Same as new:
■ Reservations only in indispensable operations
■ Wrap queries in transactions
● Requires changes to the new quota driver interface:
○ Instead of the counting
○ Have both
● Could be a future implementation

16. Create with concurrency = 10

17. Get usage with concurrency = 10