Include this as part of checksum calculation?

You mean platforms integrating with BR want to include this as part of checksum? Not necessarily.
They may just need to know the total size of each backup.

BR should provide the total size of one backup considering following cases:
...

That's a good feature request! And it would be easy to implement. What we need to do is,

1. Add a new field uint64 size = 10 to backup.File https://github.com/pingcap/kvproto/blob/5dbce7e7b868a1a19be3a368f9ea6db120ea8926/proto/backup.proto#L42-L54
2. Adjust TiKV backup writer, attach file size to the File. https://github.com/tikv/tikv/blob/134c5663340c8e868f23bc2f3273b84168aed862/components/backup/src/writer.rs#L60-L86
3. Sum up all files at BR.

Include this as part of checksum calculation?

The total_bytes in checksum calculation is a logical size, and the actual file content is compressed, so it does not match the file size.

I would like to try it ~ If I have some questions, who can I ask for help ? @overvenus

That's so cool! You can always ask me! @fredchenbj

ok, this week I would do some work about this.

The total size is already computed in #249. It just needs to printed somewhere to close this issue.

The total size is already computed in #249. It just needs to printed somewhere to close this issue.

In my test , it's already print total size.

[2020/08/23 18:46:31.324 +08:00] [INFO] [collector.go:61] ["Full backup Success summary: total backup ranges: 2, total success: 2, total failed: 0, total take(s): 0.01, total kv: 2, total size(Byte): 66, avg speed(Byte/s): 10990.76"] ["backup checksum"=1.485799ms] ["backup fast checksum"=335.652µs] ["backup total regions"=2] [BackupTS=418826134061580290] [Size=4486]

total size(Byte): 66, .

@liangyuanpeng that "total size" is the total uncompressed KV size, not the total (compressed) archive size.