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andyarnet
Contributor
Contributor
‎09-12-2016 04:54 AM

Mixing 6gb and 12gb drives in the same cluster

We are getting ready to add a few hosts to our current VSAN 6.2 hybrid cluster, which uses 1.2TB 6gb drives.  Unfortunately, the drives are EOL and our vendor is substituting 12gb drives and the corresponding controller.  Everything is on the HCL, so my question is, is this supported?  I understand that best practice is that all hosts be identical, but these are essentially the same 10k drives with the 12gb interface.

Thanks,

Andy

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5 Replies
zdickinson
Expert
Expert
‎09-12-2016 10:48 AM

It is supported, but not best practice like you said.  I would expect this small difference to be OK.  If the interfaces the drives will be plugging into are 12 gb, I might try to find a way to force them to 6 gb so you have a consistent user experience.  Thank you, Zach.

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Puneet_A
Contributor
Contributor
‎09-13-2016 05:02 AM

Hi Andy,

While mixing drives in a VSAN cluster is supported (assuming they are supported on HCL), you may have to consider a few things.

> Impact on overall performance by mixing 6gb with 12gb drives

> are you plugging the new drives in the same disk group as older one? preferably should not. If adding new nodes then simply keep the new drives in new disk group

> If these drives are EOL then you might need to figure out how to upgrade the older disks with newer ones. See VMware Virtual SAN Operations: Replacing Disk Devices - Virtual Blocks - VMware Blogs

Thanks,

Puneet

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darcidinovmw
VMware Employee
VMware Employee
‎09-14-2016 02:33 PM

Everything mentioned previously still stands as far as that this is not a preferred configuration but I will make a small point. That point is that there should be no performance difference between 6Gb SAS 10K drives and 12Gb SAS 10K drives. The performance bottleneck of your drives is still the rotating assembly. If you were getting new 15K drives or 7.2K drives then I would say that you shouldn't do it but you're still looking at the same IOPs and performance characteristics from one 10K drive to the other.

My opinion but I think it's pretty valid.

Doug Arcidino

Doug Arcidino VCP-DCV 4/5/6, VCP-DTM 5/6/7, VCAP-DCV Deploy/Design 6 If this answer was helpful, please mark it as answer I work for VMware Disclaimer: Any views or opinions expressed here are strictly my own. I am solely responsible for all content published here. Content published here is not read, reviewed or approved in advance by VMware and does not necessarily represent or reflect the views or opinions of VMware.
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zdickinson
Expert
Expert
‎09-15-2016 04:56 AM

Good morning, while I believe you are correct in the IOPS/throughput, could you see a difference in latency?  Thank you, Zach.

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darcidinovmw
VMware Employee
VMware Employee
‎09-15-2016 06:51 AM

Hey Zach,

It's possible but without knowing the specific model numbers of the drives, we wouldn't be able to confirm. I'd be interested to know.

Doug Arcidino VCP-DCV 4/5/6, VCP-DTM 5/6/7, VCAP-DCV Deploy/Design 6 If this answer was helpful, please mark it as answer I work for VMware Disclaimer: Any views or opinions expressed here are strictly my own. I am solely responsible for all content published here. Content published here is not read, reviewed or approved in advance by VMware and does not necessarily represent or reflect the views or opinions of VMware.
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