[chord] help with dhash...

[Frank Dabek]

Vijay Gopalakrishnan wrote:
> Hi,
> I recently grabbed the chord implementation from the CVS and was playing
> around with it. I managed to get sfs and chord to compile. I also managed
> to run lsd successfully.
> 
> I wrote a toy program along the lines of test_types that inserted
> <key,value> pairs using DHASH_NOAUTH and got it to run fine. There was one
> input that I typed in wrongly and realized I could not delete it. I was
> wondering if there is any way of deleting/modifying the value associated
> with a particular key. 

Deletion is not currently supported. The main difficulty is 
authenticating the identity of the delete request (public key 
authenticated blocks might be more easily deleted since they can be 
modified securely)

This brings me to my second question; how is the
> data actually stored? I am not running the loop-back file system client.
> Is it stored in the database? What is the merkle tree used for?
> 

It is stored in a DB3 database. The merkle tree is used to synchronize 
replicated blocks between replicas (e.g. replace lost replicas when 
nodes fail).

> I would really like to have the ability to delete entries because in the
> long run, I plan to try to use this setup as a distributed dictionary.
> 

One possiblity might be to cause blocks to be automatically deleted 
after a fixed amount of time. The inserter would then be required to 
periodically refresh the blocks it wished to stay in the system.

> Thanks,
> Vijay
> 
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