Choose a drive that can read your retained tape generations before sizing its capacity. Compare native capacity and the formats each generation can read or write, then check the exact library configuration.
LTO Capacity and Speed by Generation
Transfer rates in this table are generation-level published maxima. A specific half-height drive can have a lower rate than a full-height drive of the same generation. Use the exact drive model for a backup-window quote.
| 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.
LTO generation details for retained media
Read and write support through LTO 7
Through LTO 7, a drive reads its own generation and the two previous generations when those earlier generations exist. It writes its own generation and the immediately previous generation. For example, an LTO 7 drive reads LTO 5 media but writes only LTO 6 and LTO 7 media.
This format rule does not establish the host connection or library assembly. Match the host interface and drive sled and height to the installed system as well.
LTO 1 media and restore planning
LTO 1 is the first generation. Use LTO 1-compatible hardware and the original backup application to recover retained cartridges.
The cartridge format does not establish enclosure compatibility. Check the exact drive or library configuration together with host attachment and encryption-key requirements.
LTO 2 media and restore planning
LTO 2 reads and writes its own generation and LTO 1.
The cartridge format does not establish enclosure compatibility. Check the exact drive or library configuration together with host attachment and encryption-key requirements.
LTO 3 media and restore planning
LTO 3 reads and writes its own generation and LTO 2. It can also read LTO 1 media without writing to that older format.
The cartridge format does not establish enclosure compatibility. Check the exact drive or library configuration together with host attachment and encryption-key requirements.
LTO 4 media and restore planning
LTO 4 reads and writes its own generation and LTO 3. It can also read LTO 2 media without writing to that older format.
The cartridge format does not establish enclosure compatibility. Check the exact drive or library configuration together with host attachment and encryption-key requirements.
LTO 5 media and restore planning
LTO 5 reads and writes its own generation and LTO 4. It can also read LTO 3 media without writing to that older format.
The cartridge format does not establish enclosure compatibility. Check the exact drive or library configuration together with host attachment and encryption-key requirements.
LTO 6 media and restore planning
LTO 6 reads and writes its own generation and LTO 5. It can also read LTO 4 media without writing to that older format.
The cartridge format does not establish enclosure compatibility. Check the exact drive or library configuration together with host attachment and encryption-key requirements.
LTO 7 media and restore planning
LTO 7 reads and writes its own generation and LTO 6. It can also read LTO 5 media without writing to that older format.
The cartridge format does not establish enclosure compatibility. Check the exact drive or library configuration together with host attachment and encryption-key requirements.
LTO 8 media and restore planning
LTO 8 reads and writes its own generation and LTO 7. It does not retain the older two-generation read window.
The cartridge format does not establish enclosure compatibility. Check the exact drive or library configuration together with host attachment and encryption-key requirements.
LTO 9 media and restore planning
LTO 9 reads and writes its own generation and LTO 8. It does not retain the older two-generation read window.
The cartridge format does not establish enclosure compatibility. Check the exact drive or library configuration together with host attachment and encryption-key requirements.
LTO 10 media and restore planning
LTO 10 reads and writes LTO 10 media only. Its format does not read LTO 9 cartridges. Keep readable hardware for the older archive during a transition.
The cartridge format does not establish enclosure compatibility. Check the exact drive or library configuration together with host attachment and encryption-key requirements.