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32 disks to 4 RAID port?

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March 1, 2011 9:13:46 AM

Dear Community!

I have a question about a RAID hardware concent. We have an LSI Megaraid 9260-4i RAID controller. We would like to extend our RAID array but it has only 4 internal ports. It supports 32 SATA hard drives according to its properties. Could you please tell me how is it possible? Are there some kind of expanders available with which I can connect multiple drives to only one port? And is it available any perfomance drawbacks when multiple drivers are connected into only one port?

Thank you for your answers!

Regards,
Jeremy

More about : disks raid port

a c 300 G Storage
March 1, 2011 5:04:16 PM

While GhislainG is mostly correct, I believe that it's not just a cable. You need a device called an "SAS Expander," or "Port Expander," which presents one SAS connection to the card and up to eight SAS connections for drives. These don't work with all SAS controllers; the controller has to support expanders, and your does.

The User's Guide, for example, states that "You can connect one device per SAS PHY unless you use an expander." (a PHY is a one physical connector)

Edit:
Typically, these are implemented in an external drive rack that has four SAS or SATA connections which are then expanded to however many the device holds. It sounds to me like your drives are internal to your server, which means that you would have to find standalone internal expander cards. Does your chassis really have room for 32 drives? For a roll-your-own internal example, look at http://www.servethehome.com/sas-expanders-diy-cheap-low... .

It starts getting pricey if you need external room for all those drives. An example which I chose at random: http://www.pc-pitstop.com/sas_cables_enclosures/2u24.as...
a b G Storage
March 3, 2011 9:11:00 PM

GhislainG said:
Each internal port will support up to 8 drives if you buy the right cable (SAS or SATA).

The documentation indicates:
o Maximum reads: 2,875MB/s
o Maximum writes: 1,850MB/s

http://www.lsi.com/storage_home/products_home/internal_...


That is incorrect! There is no such thing as Each internal port will support up to 8 drives if you buy the right cable (SAS or SATA)

SAS controller requires SAS expander to see more drives. SAS is a daisy chain-able bus, therefore you can go up to 128 HDD (vary with host adapter) with multiple SAS expander.

To expand to 32 drives, I assume you will use these added HDD as external. Here what you need:

1x Internal to external SAS module MSAS36-2601P or equivalent

2x SAS expander 16 bay 3U RM16-S6E

a) Use #1 to convert internal miniSAS 8088 to external mini-SAS
b) Daisy chain two of RM16-S6E, then connect the 1st chassis back to the external mini-SAS (a)

Run the RAID GUI, you should be able to see and create raid(s) volume with 32x drives
!