Hello Hilko,
Monday, May 12, 2014, 12:41:51 AM, you wrote:
>> and there'is another possible problem that seems is not addressed by
>> AoE protocol: possible packets duplication on ethernet level that can
>> be caused for example by bad network topology, failing hardware (I've
>> seen semi-dead network switches that flooded ethernet segment with
>> duplicated packets) and so on?
HB> I don't see how duplicate frames could become a problem as their content
HB> is left intact.
Assume we have two ATA write commands, first sent at time 0, second at time
1. Both writes data at overlapping locations, but data bytes at overlapped
region in second command are not same as in first one. This can happen -
data on HDD not only written once and forever - it gets modified
sometimes. And lets suppose we have some network hardware that will
decide to send first packet one more time a bit later - say at time
moment 2. So finally we will have a data corruption. Note that AFAIK
ethernet standard doesn't guarantee nor delivery, nor ordering, nor
counting.. Actually it doesn't guarantee anything :)
So my myself I'm going to implement tags tracking since WinAoE uses
monotonic incrementing that allows to leverage risk of such a problem.
However AoE protocol docs says that clients can use 'tag' field to
whatever they wish, so its not a generic solution - just a workaround
(for my paranoia:) ) that bases on particular WinAoE driver implementation.
--
Best regards,
Killer{R} mailto:support@xxxxxxxxxxxx
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