[ENBD] Anyone got swapping over NBD-2.4.25 working?

[David Chow]

I seems lots of people looking for swapping over network? I have run 
diskless computers on my production system for more than 1 year. I 
tested the nfsswap from 2.2 to 2.4 . Now testing some nfsswapping code 
on 2.4.17 .  It seems very stable although there are some changes in the 
swap code after 2.4.14 . But it should work fine (not tested).


I would also like to implement something like swapping over nbd since it 
should be more efficient. It seems swapping over nbd is working at the 
moment. Any idea to share and get started? I would like to join...

Thanks.

David

Peter T. Breuer wrote:

>"A month of sundays ago Alan Messer wrote:"
>
>>Peter T. Breuer wrote:
>>
>>>I suspect that udp would not cause any memory deadlocks.
>>>
>>Certainly UDP would improve the performance. Does ENBD provide its 
>>own recovery mechanisms? Since I'd hate to lose a page.. :)
>>
>
>No - that's why enbd goes over tcp. But if you really trust your medium
>I see no reason why you shouldn't use udp. A duplex fast ethernet
>connection over point to point crossed cable should be OK!
>
>The implementor of udp would have to implement such recovery mechanisms
>as seem appropriate. I'd vote for none. After all, you HAVE to trust
>your memory.
>
>>Indeed, that what I thought. Although may be it buys to a little 
>>more time until it dies.
>>
>
>You can even get stuck trying to kill a stuck process in weird ways, or
>trying to read its present directory by running across /proc.  Yes, you
>can win some time, but it's not worth the effort, I think.
>
>>I added the 'mlockall' to the nbd-client as you suggested and in 
>>my initial tests it worked like a charm! Ran it under very heavy 
>>load for about 2-3 hours and apart from running very slooowwwwily, 
>>it didn't crash at all. However, you need to be careful to remove 
>>the NBD swap partition before you do a reboot, since it'll kill 
>>the nbd-client and leave your swapper with no where to swap. (Not 
>>good!).
>>
>
>Interesting. I imagined it would lock up way too much memory to be
>useful. If that is the case, try and work out how to limit it a bit
>(to what?).
>
>>I'll let you know if I have any other problems, but I suggest 
>>others give it a try too. If it works fine, I'd definitely suggest 
>>that you should be tempted to put it in the main code with a 
>>'--swap' option.
>>
>
>Yep. I'm not very keen on mlockall because it's a libc6 -only
>function, and I like to stay compatible with libc5.
>
>Peter
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