Status: New
Owner: ----
New issue 766 by [email protected]: Don't override disk_cache settings
for RBD disks
http://code.google.com/p/ganeti/issues/detail?id=766
What software version are you running? Please provide the output of "gnt-
cluster --version", "gnt-cluster version", and "hspace --version".
gnt-cluster (ganeti v2.10.1) 2.10.1
Software version: 2.10.1
Internode protocol: 2100000
Configuration format: 2100000
OS api version: 20
Export interface: 0
VCS version: (ganeti) version v2.10.1
hspace (ganeti) version v2.10.1
compiled with ghc 7.6
running on linux x86_64
What distribution are you using?
Debian Jessie (testing)
What steps will reproduce the problem?
1. disk_cache settings other than none will be overridden by ganeti despite
RBD being completely safe and well behaved when it comes to live migration
and other cache sensitive issues.
2. See https://groups.google.com/forum/#!topic/ganeti/loF_Gp6hHew and
especially the reference to
https://www.mail-archive.com/[email protected]/msg06890.html in
that thread.
What is the expected output? What do you see instead?
ganeti should treat RBD like DRBD when it comes to cache safety.
Please provide any additional information below.
Since the check that does the override lumps all externally mirrored disks
into the same unsafe pot (and some of those probably are unsafe with
caching) I don't know what the best way to solve this from a programming
PoV is.
If making an exception for RBD is too involved maybe changing the override
to a stern warning "you better know what you're doing" might be the faster
way forward.
Fixing this ASAP would vastly improve performance with RBD, especially with
RBD Cache in the userspace model.
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