Libvirt migrations with rsync are slow
Affects | Status | Importance | Assigned to | Milestone | |
---|---|---|---|---|---|
OpenStack Compute (nova) |
Fix Released
|
Wishlist
|
Marian Horban |
Bug Description
Setup:
CentOS 6 + RDO Icehouse (code seems to be the same in trunk)
When doing a nova migrate, the actual backing disk file is copied over with rsync. I assume the code came from this report
https:/
The rsync code uses the "-z" flag for compression. This is probably fine for cases with lightly used disks. However, with a disk full of content, it gets very slow. Rsync is not multithreaded so with a single E5-2670v2 core, we get ~12MB/s transfer speed (CPU bound). With the modest compression that is achieved this is significantly slower than no compression.
If possible, some speed test should be done without compression for disk files with different content. There might not be a reason to use compression here at all.
tags: | added: live-migration |
tags: |
added: migration removed: live-migration |
Changed in nova: | |
status: | New → Confirmed |
Changed in nova: | |
milestone: | none → liberty-rc1 |
status: | Fix Committed → Fix Released |
Changed in nova: | |
milestone: | liberty-rc1 → 12.0.0 |
Actually this is not live migration. It's "nova migrate", i.e. shut down vm, qemu-img convert, rsync over file, start vm.