11-29-2011 01:40 AM
Hi,
Uni-directional DRE impacts the way that signatures and and Chunks are stored :
How can the Datacenter WAAS determine if the data has previously been seen (and generate a signature), when it does not have the original data stored ?
If data chunks aren't stored, then only the signatures can be used to determine if the data has been previously seen :
Does this mean that signatures are uniquely generated from data (i.e. two different data chunks can't generate the same signature) ?
Best Regards
Finn Poulsen
Solved! Go to Solution.
12-07-2011 04:18 PM
Hi Finn,
So, here is the answer to your questions.
1. DC-WAAS will not remove the signature unless asked to do so or eviction kicks in.
2. If peer A has no signature / chunk, it will generate NACK to DC WAAS for the signature packet and then DC-WAAS will send out data to peer A if it has signature.
Hope thsi answers your questions.
PS: Please mark this as Answered, if this answers your question.
11-29-2011 01:41 PM
Hi Finn,
Answers for you:
How can the Datacenter WAAS determine if the data has previously been seen (and generate a signature), when it does not have the original data stored ?
Ans: This is uni-Directional so DC WAAS is not going to store it on disk.
If data chunks aren't stored, then only the signatures can be used to determine if the data has been previously seen. Does this mean that signatures are uniquely generated from data (i.e. two different data chunks can't generate the same signature) ?
Ans: Yes, signatures are unique but will be same from same chunk of data.
Hope this helps.
Regards.
PS: Please mark this as Answered, if this answers your question.
11-30-2011 12:43 AM
Hi Bhavin,
Thanks - just to fully understand the uni-directional behaviour (internally in the Datacenter WAAS) :
A) TCP Session 1 to peer A flows through DC-WAAS, which (consider an empty DRE cache) :
B) TCP session 2 to same peer flows through DC-WAAS
....
C) Some time later WAAS Peer A evicts the chunk due to DRE aging :
Questions :
1) Is above described behaviour basically correct (don't need entire mechanism :-) ?
2) How is this signalling, described in C) above, done - if my description is correct ?
Best regards and thanks
Finn Poulsen
11-30-2011 05:05 PM
Hi Finn,
I need to work on this with internal resources here to answer your questions. I will post the update for you soon.
Thanks,
Bhavin.
12-07-2011 04:18 PM
Hi Finn,
So, here is the answer to your questions.
1. DC-WAAS will not remove the signature unless asked to do so or eviction kicks in.
2. If peer A has no signature / chunk, it will generate NACK to DC WAAS for the signature packet and then DC-WAAS will send out data to peer A if it has signature.
Hope thsi answers your questions.
PS: Please mark this as Answered, if this answers your question.
12-12-2011 09:08 AM
Thanks a lot
Finn
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