LTO-4 support question

[deathmock5]

General Question, Why is Lto4 not supported? Is there some hardware limitation or something? Just curious, I do have some experience with C and C++ and wondering if its just a "We haven't gotten around to it" kinda thing, or something in the device prevents it.

Figured Id ask before diving headlong into a new project.

[retokromer]

LTFS was introduced with LTO-5.

[piste-jp]

Because LTFS requires 2 or more partitions on a tape.

The partition feature was introduced into LTO5.

[deathmock5]

Ah, ok I was under the impression this was a file system that's written onto a raw tape itself.if I'm understanding right, It's instead leveraging device calls that only exists in the newer devices to set partitions.

Would it be possible to just write the data to the tape in a raw form? By having the filesystem headders written to the tape in blocks? Cause if thats the case I'm wondering if it's possible to create a ltfs file table as a virtual image with the data. And then dd it to older tapes. Unless there's something specific preventing it.

[piste-jp]

Would it be possible to just write the data to the tape in a raw form? By having the filesystem headders written to the tape in blocks? Cause if thats the case I'm wondering if it's possible to create a ltfs file table as a virtual image with the data. And then dd it to older tapes. Unless there's something specific preventing it.

I'm not sure how much you are familiar with tape device (SCSI stream device). But it is great if we can do this kind of thing.

Technically, it could. But there might be multiple aspects.

1. Is using old tape device, LTO4 is already disconnected from support I think, good strategy for using development effort?
   • Real tape capacity might be a problem when we are using virtual image
   • We need to have a large disk to hold virtual images anyway
2. Tape data stream shall not be a simple, because it need to treat variable block length

---

We already have 2 implementations that are similar to this idea.

1. ITDT backend, this enables to access to tape image file captured by ITDT, a tape tool provided by IBM. This backend only supports reading an image from LTFS
2. file backend, this backend provides tape mimic interface to LTFS with files under a directory. This backend generates 1 file for 1 block on tape

[deathmock5]

Would it be possible to just write the data to the tape in a raw form? By having the filesystem headders written to the tape in blocks? Cause if thats the case I'm wondering if it's possible to create a ltfs file table as a virtual image with the data. And then dd it to older tapes. Unless there's something specific preventing it.

I'm not sure how much you are familiar with tape device (SCSI stream device). But it is great if we can do this kind of thing.

Technically, it could. But there might be multiple aspects.

1. Is using old tape device, LTO4 is already disconnected from support I think, good strategy for using development effort?

   • Real tape capacity might be a problem when we are using virtual image
   • We need to have a large disk to hold virtual images anyway

2. Tape data stream shall not be a simple, because it need to treat variable block length

We already have 2 implementations that are similar to this idea.

1. ITDT backend, this enables to access to tape image file captured by ITDT, a tape tool provided by IBM. This backend only supports reading an image from LTFS
2. file backend, this backend provides tape mimic interface to LTFS with files under a directory. This backend generates 1 file for 1 block on tape

I'm extremely unfamiliar with the caviats of tape.

As for lto4 not having support, tape is still in some cases prohibitivly Expensive, while lower lto versions do have good storage lengths in comparison to standard HDD. And can still be beneficial to hobbyists.

I'll look into thoes other repos.