CRC vs HASH in Health Check

[balma01]

Whay during Health Check it performs a CRC check for metadata and an HASH check fo the data ? Which is the main difference?

[Gostev]

I'm not sure I understand your question. If you're asking about some user interface messages, then please share a screenshot. Thanks!

[balma01]

Hi Gostev
I'm reading the documentation that states: During the health check, Veeam Backup & Replication performs a CRC check for metadata and a hash check for VM data blocks in the backup file to verify their integrity...
My question is about the 2 different checks (CRC and HASHES), which is the main diffrenece, why veeam decided to implement 2 different checks and so on.

[Gostev]

Consider it largely the same thing, just different algorithms since use cases are different. For CRC algorithm, collisions are much more likely, so this algorithm should not be used for dedupe (but is just fine for metadata integrity verification). For hashing of data blocks, we use a different algorithm which is much less likely to have a collision.

[balma01]

Thankg Gostev,
the hash values for data blocks that are stored on the VMB files checked for health, are the very same hash values used for deduplication?

[Gostev]

If you mean VBK, then yes (VBM files don't store data blocks).