Adding to P4500

[danletkeman]

Hello,

We currently have a P4500 2 node san.  We are looking at adding to it, but I am unsure if I can add one more node to a two node system, or do I have to add 2 nodes to the existing 2 node system?

Thanks,

Dan.

[giladzzz · Accepted solution]

Hi

There is no problem adding one more node to a two node cluster 

make sure it's the same capacity other wise if it has more capacity you will loose

disk space. Also if you have a 3 node cluster you don't need to use FOM.

Regards

[danletkeman]

Thanks for the quick reply.

If I have a three node cluster is network raid 5 something that is recommended or will I loose performance over the mirrored system that I have now?

Thanks,

Dan.

[giladzzz]

Hi

You can use raid 5 on a 3 node cluster i am not sure about performance

take in to account that once you add the third node your

raid 10 disks will be re-distribute on all 3 nodes.

and then you can change from network raid 10 to 5

it's an online process.

[Bryan McMullan]

Overall, you will lose IOPS using network RAID 5 over network RAID-10. 

In the past, I stayed away from NWR5 as the performance drop wasn't worth the additional capacity.  Though HP did make improvements in 9.5 they say making it closer to being on-par with NWR10.  Try adding a volume using 5 and see if the performance is up to your needs.  You can mix and match the network raid levels throughout your volumes.

[oikjn]

all that said, it is simple to just add a single additional node to the 2-node cluster and keep network raid10.  You  will gain additional stoage space which should be equal to about 1/2 of the raw storage capacity of the node.  Adding a third node has a bunch of benefits... it adds to capacity, adds to IOPs and lets you run without the need for a FOM.  Just make sure the node is the same as the other nodes or adding it can result in a net performance loss if the node is slower since performance is based off of the slowest node.

[Steve Burkett]

You also want to consider SANiQ version numbers. You'll probably get SANiQ 9.5 pre-loaded on the new node, you need to be on at least version 8.5 to be able to add a 9.5 node in to your existing cluster.

And make sure all the firmwares are up to date on it before you add it, including the SAS backplane and drive firmware.