Blu-ray disk & UDF2.60 file system

What UDF 2.5 spec says is
we need Virtual Allocation Table and Sparing Table in the file system
for Read-modify-write and defect management.

Since these are incorporated in drive only (Blu-ray disk), it is
eliminated in UDF 2.6 spec.

My question is if we don't want to support read-modify-write and defect
management in the drive how we can achieve read-modify-write and defect
management.

One probable answer is:

we can support above features in software itself. above this UDF file
system will sit.

any comment or other way to achieve for this.

Thanks

Guru

guru.naveen@gmail.com