SAN / EMC: CX4 DAE (Drive Shelf) Information
This will not get very detailed, but I figured I would share the following information. In light of not being happy with the typical “each shelf has a 4 Gig interconnect” statement, I kept checking until there was a better answer. So, anyone working with EMC SANs typically knows that every shelf is connected to each SP (Service Processor – 2 per SAN), daisy chained in a specific loop, and assigned a shelf id. Next is the LCC.
Each DAE contains 2 LCC interfaces. LCC is the acronymn for “Link Control Card”. Typically one LCC goes to each Service Processor. So that means that each DAE has two 4 gig links for a total of 8gb theoretical throughput.
This is where I will be reading more information. Just because you have 2 LCC cards, each LUN can only be assigned to 1 Service Processor! If my theory is correct, that means if all drives in one shelf is dedicated to a single LUN, and that LUN can only be active on one SP, does that mean that the actual throughput will be limited to 4gb instead of 8? This being due to the other LCC loop being connected to the SP that is not assigned control of that LUN.
Any thoughts? Feel free to comment!
Yes you have the right idea. The CLARiiON CX4 series has 4 Gb/s throughput end-to-end. What model CX4 are you working with? Also what is the configuration (# of DAE’s, types of disks, etc). And finally what are you trying to do that needs more bandwidth, we can probably help you come up with an alternative disk/LUN layout that gets what you need.
Also don’t forget unless you have the new 8 Gb FC or 10 Gb iSCSI (are those even out yet?) UltraFlex I/O modules you are going to be limited to 4 Gb ports anyway (yes I realize you could have anywhere between 2 and 12 per storage processor depending on the array type and how you’ve populated things) – but don’t forget ALL the traffic on the array is flowing through those.
Give me a better idea of what you have and what you want and I’m sure we can figure something out. :)
Andrew Storrs said this on May 29, 2009 at 11:49 pm
It is a CX4-240. performance is not an issue currently setup with 100 – 400g 10krpm and 15- 300g 15krpm disks. All raid groups setup with raid 10. The highest IO luns were vertically striped between 2 DAEs. One at the end of the first bus and other at the start of the next. I just wanted to make sure the logic was correct concerning the LCC links.
kcollo said this on May 30, 2009 at 9:50 am
“The highest IO luns were vertically striped between 2 DAEs” Did you create RAID groups and LUNs that spanned DAEs or did you use MetaLUNs?
Andrew Storrs said this on May 30, 2009 at 1:59 pm
[...] CX4 DAE (general) information http://blog.colovirt.com/2009/05/29/san-emc-cx4-dae-drive-shelf-information/ [...]
SAN / EMC: Clariion CX4 Solid State DAEs (Shelves) « Colocation to Virtualization said this on June 3, 2009 at 4:01 am