Why LTO-10 fell short on speed and backward compatibility

https://blocksandfiles.com/2025/07/29/tape-engineering-changes-from-lto-9-to-lto-10/

by bilegeek • 9 months ago

21 9 9 months ago

blocksandfiles.com

dale_glass2• 9 months ago

What's with all this "compressed capacity"? Does that apply anywhere tape is used these days?

I mean, if you're backing up multiples of 36 TB of anything, I would guess that most of it is already compressed.

noir_lord2• 9 months ago

Native is iirc 30TB - they quote compressed capacity but eh that's very much going to depend on what you are storing and how compressible it is.

And you'll have a rough idea what it is you are going to be storing and how compressible it is if you spending that kind of money.

It's marketing and a little skeezy to quote it and I bet they have some justification for why they arrived at 2.5:1 compression.

EDIT: Yeah it's 30TB - been many years since I had anything to do with LTO but they use a modified version of LZS called SLDC so it's that that they are assuming will get 2.5:1 on "random enteprise data that isn't already compressed" the 2.5 threw me as well because that used to be 2:1 so either they improved SLDC or thought they could wing it - looks like that switched between LTO-5 and LTO-6.

nyrikki• 9 months ago

When you try to compress highly compressed or random data the size expands.

At least on the LTO tape drives I have used, will disable compression if the size is larger in an adaptive way.

As tape read and write speeds depend on data size, it is still worth the effort to try and opportunistically compress data on drive.

As this can usually be done without stopping or slowing the tape, there really isn’t much of a downside.

As for the compressed capacity, that is just 30+ years of marketing conventions, which people just ignore as it has always assumed your data was 2:1 compressible.

noir_lord2• 9 months ago

2.5:1 now apparently, showing my age because I had to go look because last time I had anything to do with LTO it was still 2:1 - guess they got PiedPiper to update the SLDC spec ;).

nightshift12• 9 months ago

File compression requires additional storage, memory and processing power. Why bother if the tape appliance already handle it ? Data is unusable in compressed format and is hard to deduplicate. Also, often, there is already compression at the storage array level but the data is decompressed when read.

dale_glass2• 9 months ago

What data is unusable in compressed format?

Images, videos, music are compressed. RAWs from my camera are compressed too. Even log files tend to be compressed.

What else do people store that would amount to multiples of 30TB and not already have some form of compression?

UltraSane• 9 months ago

LTO is normally used with high-end backup software like Commvault that compresses and dedupes backups before writing them to tape.

guerby• 9 months ago

Using LTO7 and LTO9 with Proxmox Backup Server at work.

Both do about 300 MB/s

Easy to remenber : 1 TB per hour per drive

Why LTO-10 fell short on speed and backward compatibility

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