Not using BUS 0 on a VNX5600

My opinion is that you should recable it with alternating buses.  For example, the first few DAE's would be 0_0, 1_0, 2_0, 3_0, etc....

This allows for all buses to be used early on in the expansion. 

Mike

I agree that all the available buses should be utilized. However, if they are not, it will not cause a performance issue, will it?

0_0 is the DPE - it is VNX5600. It is already up and running.

It will cause in imbalance.  Depends on how hard you push the array and the other available buses.  Also, if you dont have 0_0 cables, im not sure if it will work.  I believe vault has to be in and cables to 0_0

Does it have any lag?

As per EMC that config would not be correct confid Ad-astra.

Will it work? Yes practicality it should

Will that create a problem? High chances of yes

And if there is a performance issue then the first recommendation would be to re-configure.

Maybe it is worth re-cabling the array and utilizing all the buses?>> Oh yes

Regards,

Sheron.

Thanks Sheron, please see my comments on bold.

Does it have any lag? - Unknown, there is no production data on it yet. As per EMC that config would not be correct confid Ad-astra. - This is funny, because EMC field services engineers cabled it this way, omitting bus 0. I guess, if it goes against EMC best practices, they should have brought this up, not me, after it is cabled and initialized. Will it work? Yes practicality it should - It does work, at least it is up and running, no prod data on it yet. Will that create a problem? High chances of yes - Why will it create a problem? Could you elaborate on this. And if there is a performance issue then the first recommendation would be to re-configure. - I agree, but it will depend on the nature of the problem. Maybe it is worth re-cabling the array and utilizing all the buses?>> Oh yes - I agree, just wanted to find out what complications may come out of it.

If this no prod data on it, I would re-cable. Like I said, off the bat, your Buses wont be balanced as Bus 0 wont be in use.

Here is what could help us

https://support.emc.com/docu47537_VNX5600-Hardware-Information-Guide.pdf?language=en_US

From page 128 to be precise.

Honestly I can think of many issues but cant find any docs to prove my point. Gimme a lil more time to think to figure what could be the issue.

Regards,

Sheron

No, thank you, but I still cannot figure out if there will be any errors, issues down the road, if bus 0 is not in use.

As per what I understand I would think think that the BUS 0 is kept only for the DPE.

So BUS 0 is free at the moment if we need to add any enclosure to it.I should be able to use the BUS 0 for future use.

Error: ?? , i was thinking about any parity mismatches due to the way the array is connected.

However how practical is the error to show up is something I honestly dont know.

Can you check with the support team and see what they think of it.

If you get a green flag from them then , yaaaaay, we are good.

If they say no can you let us know why, as it would help me clear my doubt.

Thank you Ad_astra, you made me think a bit today

Im not sure about Errors. I would think not if you have the DPE on 0_0, you technically don’t have to use a bus if you don’t want. The wiring diagram shows multiple ways to wire and one of those ways is to Grow by buses instead of enclosures meaning instead of cabling like this 0_0, 1_0, 2_0 you would cable 0_0, 0_1, 0_2. It doesn’t specifically show this on Bus 0 but from an error perspective I cant think of any. Again, my concern would be performance but only when you are pushing the array to its limits. If you are doing 20K IOPS it wont be a problem. If you are doing more, your mileage may vary. Just out of curiosity, you have the opportunity to cable it correctly and place the array in an optimal state. Why would you not do that?

Mike

Good Deal then. That would be my only concern is at its limits.

I will absolutely recable it. Just wanted to find out out of curiosity if leaving bus 0 empty will cause any issues down the road or not, as I could not see any reason why it would cause any performance issues. The array is not going to be pushed to its limits that is for sure, as it is a DR array, even if the failover occurs it's never going to get super hammered, as not all production machines are going to be stood up at this location.

Ad_Astra,
Yesterday I had a conversation with a VNX engineer. After much we came to a conclusion that in our scenario the BUS0 is taken internally that talks with the drives in your DPE and them only. This config SHOULD not cause any issues. So, that makes me go back and check why I thought it would cause any issues (D'Oh)

It was an awesome question thank you.

I am also hopeful that someone might come with another idea, will wait

Regards,

Sheron

Your DPE will be using BUS0.

Are there any SSD's in the DPE ? That would take some load off the other bus's.

Lucky you have the SAS Expander SLIC