2011-03-25 01:52 PM
I would like to know your suggestions regarding the disk shelve stack count for a FAS6280AE + 16 DS4243 600SAS configuration with 4 quad port HBA's in each controller.
My idea was 4 stacks with 4 shelves.
Does a 2 stack configuration have any advantages or disadvantages performance wise?
What is recommended? Fill up a stack first or balance the shelves to more stacks if possible?
Please let me know what you think. Thanks!
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2011-03-25 04:06 PM
My 2 cents would be:
DS4243 has 3Gbps SAS interfaces, 4 lanes. So 12 Gbps max.
2 stacks of 8 shelves, means 1 stack per controller. I.e. 192 disks on 1 stack. Max is 10 shelves, or 240 disks.
4/4: 2 stacks of 4 shelves per controller, more SAS bandwidth, but also requires more PCIe slots, and more complex cabling.
What are your needs aggregate wise ? That can also influence your design.
2011-03-25 05:49 PM
Are you putting each stack in a separate rack? If not, then you could have downtime later to move shelves so you can add more disks... I like the idea of 4 stacks, but if 2 stacks saves you from having to move shelves later, then it is a better option since you can add stacks 3 and 4 later as new stacks.. but if you won't exceed your current rackspace, then 4 do make sense. Do a cable audit since you might need some additional cables of different lengths than the ones that shipped if the shipment assumed 2 stacks. With MPHA, you get 24GB/sec to the back of each loop with 2 paths of 4x3GB lanes...so bandwidth to the shelves shouldn't be a bottleneck.
2011-03-30 12:48 PM
thanks for your ideas.
Im gonna stick with my 4 stack configuration in 2 racks, starting the lower IDs in the middle of the racks so I can extend the stacks in future.
2011-03-30 02:37 PM
I'd recommend number each stack with room to grow. So the first stack has disk shelves 11,12,13,14, the second stack 21,22,23,24, the third stack 3x, forth 4x. This'll make it really easy to identify and also really easy to expand without too much forward planning.
Stretching a stack into a different rack isn't too much of an issue, you can get 5m SAS cables I believe and this is more than enough to stretch to the next rack if needed.
I second the 4x4 approach. As you say, the best back-end performance. Additionally it's the highest level of resiliency as you have to lose more loops to make something catastrophic happen! Just make sure you split all the SAS connectivity across multiple IO boards (PCIe or onboard).
2011-03-31 01:02 PM
thats exactly what Ive done
connected to all 4 pcie sas cards.