天空вℓσи∂ [Unemployed edition] @skyblond@social.cleverlibre.org

Just found out 7z is not the best format for archiving. It has to go back to the header when finishing the archive. This rewrite cause LTFS to copy the whole data block resulting a huge waste space.

Simple fix: write the 7z to disk and then copy it to tape.

So, on pure Windows solution, I have no access like char device file and command like `mt`, the only solution I have is LTFS.

By formating LTFS everytime before use, it's kinda like `mt rewind`. Also I can set the volume name to the date of backup, which, kinda be helpful.

Also, on Windows, I use 7zr (the console version of 7z) with compression level 0 to tar ball everything. One important feature I need is the ability to exclude folders, like $Recovery and "System volume information" etc. That rule out zip command.

Well, although windows is suck, the powershell is not bad. I like it more than bash.

This is technically a backup. While cygwin has some performance issue with pipe, I can avoid that by letting dd read the whole disk and write to tape.

It's hard to read (have to dump to a spare disk then pick the file I need), but it still cound as a backup, I guess.

Tried a bunch of method to speed up/buffer the write speed to tape drive in Cygwin. Then found out the pipe itself has performance issues.

With `dd if=/path/to/test/file of=/dev/nst0 bs=4M`, it can easily get 160MB/s writing speed. But with `dd if=/path/to/file bs=4M | dd of=/dev/nst0 bs=4M status=progress`, I can only get about 65MB/s.

That's not usable.

小剧场（

Wrote a hacky bash script using LTOEnc (a windows cli tool for setting up LTO hardware encryption) and tar to backup my PC. (Using Cygwin)

But I'm confused with `tar -b`. With larger blocking factor, each record get bigger but when dealing small files there are more space wasted. I'm backing up both C and D drive, where D drive lives my code and movies/animes/shows.

Don't want to be too extrem on parameters, so I use `-b 1024` and enabled compression to make balance.

Also enabled encryption. While I don't want to encrypt long time archive, backup is a more short term thing, which I'm pretty sure I won't forget the password.

Should be fine I guess? Now I'm testing it.

Want to test how good the hardware compress is. So I decide to test is using block number. I assume the block number will be smaller if compression reduce the total amount of data write to tape.

But then I suddenly realized, that compression is transparent to the system. No matter compress or not, the block number is same since I use the same dataset to test.

So now I'm measuring rewind time😋

hmmm

looks like stenc cannot be compiled under cygwin.

Still, not found any way to enable hardware encryption of my LTO tape drive.

@fatelab 算卦 打水晶头