On 04/14/2013 09:25 AM, Stas Oskin wrote:
1) If data availability and redundancy is most important, you would go
with multiple 2U boxes to minimize cluster impacts in case of
any downtime?
My general feeling here is that it depends on the size of the
cluster. For small clusters, 2U or even 1U boxes may be ideal. For
very large clusters, it is probably fine to use a denser chassis.
It's all about the ratio of how many nodes are left to absorb the
loss when a single node fails. I don't have any hard numbers, but
my instinct is that in production I wouldn't want to lose more than
about 10% of my cluster if a node dies.
So for a 180 TB cluster you would go with a 6 - 8 drives bare-bone?
What about 500 TB?
Like I said, it's just my instinct. For a 180TB (raw) cluster you've
got some tough choices to make. Some options might include:
1) high density and low cost by just stick a bunch of 3GB drives in 5 2U
nodes and make sure you don't fill the cluster past ~75% (which you
probably don't want to do from a performance perspective anyway). Just
acknowledge that during failure/recovery there's going to be a ton of
traffic flying around between the remaining 4 nodes.
2) Lower density (1-2GB) drives and more 2U nodes for higher performance
but lower density and greater expense.
3) high eventual density and low eventual cost by buying 2U nodes that
are only partially filled with 3TB drives with the assumption that the
cluster is going to grow larger down the road.
4) 15 4-drive 1U nodes for less impact during recovery but greater
expense and lower density.
All of these options have benefits and downsides. For production
cluster I'd want more than 5 nodes, but it wouldn't be the only
consideration (cost, density, performance, etc all would play a part).
2) Barring service and SLA, is it really worth taking HP over
SuperMicro, or it's simply overpaying for a brand?
I've had great experiences with both Supermicro hardware and HP
hardware. Products from both companies can work great for Ceph, but
they are different companies and have different benefits and
downsides. Service, support, and price are all things that may make
one or the other a better fit depending on your needs.
I see, thanks.
--
Mark Nelson
Performance Engineer
Inktank
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