Wido den Hollander пишет:
On 06/24/2015 05:11 PM, Dzianis Kahanovich wrote:
I plan to migrate cluster from straw to straw2 mapping. Ceph and kernels
is up to date (kernel 4.1.0), so I want to change directly in crush map
srew to straw2 and load changed crush map (by steps - per host and
rack). Are this relative safe and must be remapped runtime?
It really depends on your situation. My big question is though, why do
you want to go to straw2?
As described, straw2 will make less changes on stress. So, if in future I will
replace or add HDDs (2T -> 4T, move 2T, etc) it must less "repair" works. To
make less stress on stress, in short.
In a situation where all hosts are equal in size straw2 doesn't change
anything. It makes a difference where you have a lot of unequally sized
hosts.
You can test this by fetching you crushmap from the cluster and perform
tests on it with 'crushtool'.
That will tell you what the differences will be between straw and straw2.
Yes, now I change 1 (of 4) host (3x2T same HDDs) to straw2, no visible changes.
Even restart this OSDs. But I have a bit different hosts (3x2T not precise equal
to 6x1T, and want to bay some 4T). Also I apply "hammer" tunable.
Now I will think and look some days before move other 3 host and whole rack. And
may be wait issues there.
--
WBR, Dzianis Kahanovich AKA Denis Kaganovich, http://mahatma.bspu.unibel.by/
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