RAID controller bottlenecks

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JayG30

Active Member
Feb 23, 2015
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Hello,

I'm looking to get some discussion on RAID controllers limits with some of the newer storage technology. Specifically what I'm interested in is if current hardware RAID controllers are presenting bottlenecks to all flash based storage arrays. And also how do current hardware RAID controllers handle things like NVMe drives?

I'm pretty behind the curve on all flash storage and NVMe. But it seems to me that a decent size RAID10 of all enterprise SSD's can be bottlenecked by even the best RAID controllers on the market.

My interest is use in VM hosts. On small scale I've liked the idea of having 2 hosts replicating VM data between them (cheap redundancy) with a hardware RAID and fast local storage to be a great way to go for performance, cost, and reliability. You could leverage things like cachecade if you don't go full flash storage. But with the cost of enterpirse SSD's dropping and plenty of use cases that don't call for tons of space but high IOPS, going with a full flash array isn't that crazy anymore. And it seems like the RAID controllers are getting in the way of that speed though. Things like VSAN are nice and remove the RAID controllers from the equation (for a more software based RAID) but get costly for small deployments.

Thoughts?
 

T_Minus

Build. Break. Fix. Repeat
Feb 15, 2015
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NVME don't work on standard RAID controllers. Specific ones are hopefully coming to market soon.

SSD def. do bottleneck RAID controllers, and depending on the # you use should be divided up between multiple controllers for optimum performance.
 

JayG30

Active Member
Feb 23, 2015
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So NVMe is basically a no go with RAID controller right now? So in a typical esxi or hyper-v box with hardware raid they really don't provide much use unless you want to store VMs on storage with no real protection?

I guess the only other way currently to take advantage of NVMe in a responsible manner would be vsan or other software based RAID? I think I read that vsan and others like it aren't taking advantage of NVMe as of yet either though.
 

cesmith9999

Well-Known Member
Mar 26, 2013
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NVMe is really only good in software RAID (Storage Spaces Direct, ZFS, etc...) until there is a whole new generation of HW RAID ASIC. these will only be used software based raid schemes.

We turn off write back cache on ssd arrays because it causes latency of writes to our systems.

Chris
 

whitey

Moderator
Jun 30, 2014
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So NVMe is basically a no go with RAID controller right now? So in a typical esxi or hyper-v box with hardware raid they really don't provide much use unless you want to store VMs on storage with no real protection?

I guess the only other way currently to take advantage of NVMe in a responsible manner would be vsan or other software based RAID? I think I read that vsan and others like it aren't taking advantage of NVMe as of yet either though.
vSAN definitely works w/ NVMe devices.