[Borgbackup] Determine if a chunk should be added to repository

[Joseph Hesse]

Thank you for your reply.
Is the unique id for a content-addressed storage object a 256 bit hash?  
Collisions are always possible, why doesn't Borg handle them, or, am I 
not understanding the idea behind content-addressed storage.
Thank you, Joe


On 11/17/19 11:27 AM, Marian Beermann wrote:
> No. Borg uses content-addressed storage and does not handle hash
> collisions. That's why Borg uses a 256 bit cryptographic hash
> (HMAC-SHA2, BLAKE2).
>
> -Marian
>
> Am 17.11.19 um 18:05 schrieb Joseph Hesse:
>> Hi,
>>
>> I've been reading all I can find about Deduplication.  The explanations
>> say that hashes are used to determine if two chunks are identical or
>> different.  Even though it is very rare, two chunks can have the same
>> hash and be different.  So if chunk1's hash matches the hash of some
>> chunk in the repository, it seems to me that a byte-by-byte comparison
>> has to be done before deciding whether chunk1 should not be added to the
>> repository.  Is this the case with Borg?
>>
>> Thank you,
>>
>> Joe
>>
>> _______________________________________________
>> Borgbackup mailing list
>> Borgbackup at python.org
>> https://mail.python.org/mailman/listinfo/borgbackup