Increasing XenServer_s VM density

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" summary

XenServer 6.2 removes multiple hard limits so a host can run 500 supported VMs (650 PV) by increasing event‑channel capacity, doubling blktap2 device counts, raising AIO limits to ~1,000,000 and mitigating xenstored/select fd limits; dom0 lowmem (~1MB per VM) remains a constraint until 64‑bit dom0. Dom0 CPU pressure drops by replacing xenstored polling with xenstored polling → watches and by cutting qemu callbacks (notably USB emulation throttled/optional). Measured results: 90 Windows VMs boot ~60% faster, 200 VMs boot in ~13 minutes, Login VSI stays acceptable for ~300+ VMs.

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" chapters (19)

1. 0:00Intro
2. 1:09Users expect VM density to scale with hardware
3. 1:50XenServer's VM density scalability
4. 3:08domo event channels
5. 6:04blktap2 device minor numbers
6. 7:21number of aio requests
7. 8:47domo grant references
8. 10:26connections to xenstored
9. 12:16connections to consoled
10. 12:51domo low memory
11. 13:45Summary of hard limits
12. 16:35500 Windows VMs on a host
13. 17:04Outline
14. 17:59High domo CPU utilisation by xenstored
15. 21:41qemu burning domo CPU
16. 27:14Booting 90 Win7 VMs
17. 28:39Booting 120 Win7 VMs
18. 29:12Booting 200 Win7 VMs
19. 34:25Questions