On Mon, Apr 27, 2009 at 9:49 PM, kelsey hudson <khudson@drjays.com> wrote:
[..trimming people who are on the list..]

er krishna wrote:
Thanks, to all of you for this information. So now, what I can conclude that we can connect 24 SATA hard disk having 2 TB capacity. Please confirm weather we can reach beyond this limit.

you can always use multiple controller boards, and many of the controller boards support sata/sas expanders. These break out a single SAS/SATA connector into multiple host connectors, as SAS and SATA are buses, not ports.

in the case of SAS, you can basically have 128 fanout expanders and 128 edge expanders per host connector. That gets you 16384 disks per physical SAS connector.

>>>> This is clear and thanks for it. But Can SATA hard disks be connected on SAS controller ? I don't hink our AoE will serve with SAS disks. Please confirm it.

In the case of SATA, you can get a 15-device breakout expander. This expander cannot be cascaded like SAS, so you're limited to 15 devices per connector (total).

>>> Just asking, here I am not clear. How many connectors I can connect ? Each connector will have 15 disks capacity. Is there any way to connect more than one connectors, what will be the maximum limit according to the available solution in market. I am not concerned about theoretical limits.

Note, however, that if you're using a "dumb" controller, it leaves it up to the OS to talk to the expander; in the case of Linux the expander support is rather weak. If you're using an intelligent controller like one of the Areca or 3ware RAID boards, the expander code is built-in to the firmware on the controller and abstracted away from the OS (as it should be -- if you're dealing with that many disks you want something with a more intelligent interrupt handler than x86, certainly).


Kelsey Hudson
Sr. Systems Administrator, DrJays.com
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