[Linux-HA] Questions re: USB for HB and n-node data storage
linux at alteeve.com
Mon Jul 23 07:58:01 MDT 2007
Rudi Ahlers wrote:
> Madison Kelly wrote:
>> Morning all,
>> I've been mulling over how to move to an n-node cluster... I've got
>> my two-node cluster working nicely, so this isn't critical. I just
>> want to learn. :)
>> I've not found any good docs on how to do n-node, so I've been
>> trying to think of it myself (scary!). One limitation I saw was the
>> backup serial link for HB. I was thinking that I would need n-1 serial
>> ports per server to let all nodes talk to all other nodes, but this
>> seemed problematic as I use 1U servers and I'd need to waste a
>> (precious) expansion bay for a multi-port serial card (if this was
>> even possible!).
>> So I was wondering, is it possible to use USB for HB? I think I saw
>> it mentioned that it was possible, but have seen no docs for this. If
>> it is, how possible/reliable would it be to have a USB hub for n-nodes
>> so that I'd only need one USB cable going into each server?
>> As I understand it, DRBD only supports two nodes. I know OCFS2
>> supports n-nodes as an FS, but no help if the underlying block device
>> doesn't. How do people get around this limitation? I am hoping to
>> avoid the need for fancy hardware, as we are a very small company.
>> Would OCFS2 formatted NAS device work?
>> Thanks for any pointers!
> This sounds like a great idea.
> I have one important question though, what type of USB cable does one
> use for this type of operation? And how do you overcome the problem if 2
> of the 4 node cluster is in another room (say on the second floor of the
> building), or something like that?
For the USB, I would *suspect* you would use a data transfer style cable
(cross over equiv.?)... But I am not sure, hence my question this
As for long throw, I haven't even begun thinking of this as I am still
working on the basics. For serial, I would probably use those DB9-RJ45
adapters and run a long CAT5(e) cable. Not sure if there is something
equivalent for USB. In my case, I would have the nodes in the same rack
for now. It's certainly an interesting question, and one I plan to look
at down the road as I learn more.
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