CrossPoolMigrationv2
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This page describes a possible design for Cross-pool migration (which also works for within-pool migration with and without shared storage).
This is an alternative design to [[[CrossPoolMigrationV2]]]
This design has the following features:
- tapdisk log-dirty is used to build an efficient continuous disk copy program
- this is storage-format agnostic: it doesn't require .vhd
- the SM on one host can generate URIs which can be used by other SMs to access disks over iSCSI on the storage network
- handling of iSCSI endpoints (both initiators and targets) is abstracted by an iSCSI service
- this is expected to simplify the current code and prevent (eg) a bug in one SM plugin from interfering with another SM plugin
- a single codepath is used in xapi, making testing easier
- this replaces the existing migration API
- a simple RESTful API makes the whole thing quite easy to test, prod etc.
- the xapi pieces and the SM pieces can be developed and tested independently and integrated at the end
Component diagram
Media:CrossPoolMigration$components.pdf
Migration sequence
Media:CrossPoolMigration$migrate.pdf
Proposed milestones and task list
The following milestones are proposed:
| Milestone number |
| 1 |
| 2 |
| 3 |
| 4 |
The following tasks are proposed:
| Task | Status |
| Forward-port blktap1 log dirty mode to tapdisk2 | |
| Implement an iSCSI service in dom0 | Completed |
| Modify VDI.deactivate to finish any pending copies | |
| Implement xapi HTTP operations | |
| Create a continuous copy program (use sparse_dd?) | |
| Implement SMAPI VDI.copy | |
| Implement SMAPI VDI.get_url | |
| Implement XenAPI VM.migrate, VM.receive | |
| Implement xapi HTTP heartbeat |
Links
The iscsi-target-manager is a simple python program which wraps the "tgtadm" commands used to configure an iSCSI target.
