LTO (Linear Tape-Open) capacity has roughly doubled with almost every generation since the standard launched in 2000. That makes generation compatibility, not raw capacity, the detail that actually determines whether a drive upgrade works with existing tape stock. This guide covers both: the full capacity table, and exactly which generations a given drive can read and write.
LTO Capacity and Speed by Generation
| Generation | Native Capacity | Compressed Capacity | Native Transfer Speed |
|---|---|---|---|
| LTO-1 | 100 GB | 200 GB | 20 MB/s |
| LTO-2 | 200 GB | 400 GB | 40 MB/s |
| LTO-3 | 400 GB | 800 GB | 80 MB/s |
| LTO-4 | 800 GB | 1.6 TB | 120 MB/s |
| LTO-5 | 1.5 TB | 3.0 TB | 140 MB/s |
| LTO-6 | 2.5 TB | 6.25 TB | 160 MB/s |
| LTO-7 | 6.0 TB | 15 TB | 300 MB/s |
| LTO-8 | 12 TB | 30 TB | 360 MB/s |
| LTO-9 | 18 TB | 45 TB | 400 MB/s |
| LTO-10 (current) | 40 TB | 100 TB | 400 MB/s |
The LTO roadmap extends beyond LTO-10 on paper, with the consortium targeting continued generations through roughly LTO-14 at multi-hundred-terabyte native capacity, but only LTO-10 and earlier are shipping product as of 2026.
Read/Write Compatibility by Generation
This is where most planning mistakes happen. The rule changed partway through the LTO program's history, and it changed again, more sharply, at LTO-10.
| Drive Generation | Can Read | Can Write |
|---|---|---|
| LTO-1 through LTO-7 | Same generation and 2 generations back | Same generation and 1 generation back |
| LTO-8 | LTO-8 and LTO-7 (including LTO-7 Type M) only | LTO-8 and LTO-7 only |
| LTO-9 | LTO-9 and LTO-8 only | LTO-9 and LTO-8 only |
| LTO-10 | LTO-10 only | LTO-10 only |
Two things to take from that table before ordering new drives. First, from LTO-8 onward, the old "read 2 generations back" cushion is gone; drives from LTO-8 through LTO-9 read and write only their own generation and the one directly before it. Second, LTO-10 removed backward compatibility entirely: an LTO-10 drive cannot read LTO-9 media at all. That is a real format change, not just a narrower compatibility window, and it means an LTO-9 shop moving to LTO-10 needs a plan for existing LTO-9 tapes (keep an LTO-9 drive or library on hand to read them, or migrate the data forward before retiring LTO-9 hardware) rather than assuming the new drive will simply read the old cartridges.
What This Means for an AS400/IBM i Tape Refresh
For most AS400/IBM i shops, the practical decision is between LTO-9 and LTO-10 on a current library like the TS4300. LTO-9 remains a safe, well-supported choice with a full one-generation compatibility cushion into existing LTO-8 stock. LTO-10 offers over double the native capacity per cartridge, but only makes sense as a clean break: either a shop with no meaningful existing LTO-9 archive to keep reading, or one prepared to retain LTO-9-capable hardware specifically for older tapes during a transition period.
Shops still running LTO-6 or LTO-7 drives (common on legacy libraries like the TS3100/TS3200) are furthest from current capacity, and typically see the largest single-generation capacity jump by moving straight to a current LTO-9 or LTO-10 library rather than stepping through intermediate generations.
Common Questions
Will my new LTO-10 drive read my old LTO-9 tapes?
No. LTO-10 introduced a new tape format with zero backward compatibility. An LTO-10 drive reads and writes LTO-10 media only. Keep an LTO-9-capable drive or library available if existing LTO-9 tapes still need to be read.
What is the biggest capacity jump available right now?
LTO-10 at 40 TB native (up to 100 TB compressed) per cartridge is the current largest generation, more than double LTO-9's 18 TB native capacity.
Do I need to upgrade every generation in sequence?
No. Compatibility rules apply to what a given drive can read/write, not to how many generations a library has to step through. A shop on LTO-6 can move directly to a current LTO-9 or LTO-10 library; the only planning question is what happens to existing LTO-6 tapes, which neither an LTO-9 nor an LTO-10 drive can read.