Expanding a 7400 model

[inex_77]

Hi
We have a 7400 model, 2 nodes, with 2 x 24 disk shelves. There is 32 sas drives installed(8 free slots in each shelf). We want to add more drives to the system. We use a 5+1 cpg. Are there any specific rules to follow when we want to add shelves and drives? Do the shelves need to be installed in pairs? Is it ok to add any number of drives, as long as it is an even number?

-inex

[rotorhead1]

If you talk with your HP contact, they have a configuration tool that will give you the optimum upgrade based on your requirments.

JD

[inex_77]

Thanks your reply, but I wanted to know the best practice rules in this case. I do not want to be dependent on HP.

-inex

[trireed]

Inex,
If your CPG set = 6 then its optimal to add drives in sets of 6 if you will be using same CPG and same drive type etc. The Raid striping occurs in a vertical fashion and stripes based on the SET parameter in the CPG you are using. If you add nodes you will want to add equal number of shelves to the new nodes, but if you are just adding disks and or shelves the number of disks is optimal at an even number for redundacy and RAID striping sets. All disk strips should be in there own group in vertical fashion.

Hope this helps

David R

[Richard Siemers]

Given 2 nodes, 2 existing shelves, R5 set size of 6... assumption is that your cabling follows the best practice for 2 nodes 2 enclosures in:

http://h20628.www2.hp.com/km-ext/kmcsdi ... 7590-4.pdf
(Meaning that each enclosure is on a separate SAS loop)

I don't believe adding disks equal to the set size will matter. What currently is impacting us most is the the number of drives that can be bought at once. I am currently being told that I can only buy drives for my 7200 four at a time. I don't believe this is a technical requirement, perhaps a licensing or bad marketing. Ideally, you will want your new spindles split equally between the shelves, assuming they are cabled per that doc I linked and split between the 2 SAS ports.

Adding just 1 disk shelf is supported, but I would prefer to add 2 at a time to keep both SAS ports/loops "balanced".

Probably most important is to rebalance the system after adding more capacity, I believe you should have access to systune by default on the 7000s. This will redistribute your existing data across all the spindles new/old.

[afidel]

We were told for the SFF drives that there needed to be ventricle stripes of 4, so instead of having 8 SSD's in one stripe we have two stripes of 4. I'm not sure what internal constraint drives this but there is some rule, we had to rearrange the disks for the system to initialize properly.

[inex_77]

Thanks everybody for your input.


-inex