Re: hardware heterogeneous in same pool

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Den tors 4 okt. 2018 kl 00:09 skrev Bruno Carvalho <brunowcs@xxxxxxxxx>:
Hi Cephers, I would like to know how you are growing the cluster.
Using dissimilar hardware in the same pool or creating a pool for each
different hardware group.
What problem would I have many problems using different hardware (CPU,
memory, disk) in the same pool?
 
I don't think CPU and RAM (and other hw related things like HBA controller card brand) matters
a lot, more is always nicer, but as long as you don't add worse machines like Jonathan wrote you
should not see any degradation.

What you might want to look out for is if the new disks are very uneven compared to the old
setup, so if you used to have servers with 10x2TB drives and suddenly add one with 2x10TB,
things might become very unbalanced, since those differences will not be handled seamlessly
by the crush map.

Apart from that, the only issues for us is "add drives, quickly set crush reweight to 0.0 before
all existing OSD hosts shoot massive amounts of I/O on them, then script a slower raise of
crush weight upto what they should end up at", to lessen the impact for our 24/7 operations.

If you have weekends where noone accesses the cluster or night-time low-IO usage patterns,
just upping the weight at the right hour might suffice.

Lastly, for ssd/nvme setups with good networking, this is almost moot, they converge so fast
its almost unfair. A real joy working with expanding flash-only pools/clusters.

--
May the most significant bit of your life be positive.
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