Tape library and systems vendor Spectra Logic announced LTO-10 support across its tape library product set, but IBM’s tape drive shrinks the expected capacity and loses backwards compatibility.
LTO-10 is the latest LTO tape generation and the LTO organization’s spec has specified a 36 TB raw capacity and 90 TB compressed capacity at 2.5:1 compression.
LTO tape reels are made by Fujifilm and Sony and tape drives by IBM. Big Blue’s LTO-10 tape drive only supports 30 TB raw capacity, not 36TB, and so its compressed capacity is 75 TB, while the LTO roadmap provides for “up to” 90 TB.
Big Blue says it “supports the LTO Consortium compressed specification for LTO Ultrium 10, offering up to 75 TB of data storage per cartridge (30 TB native).” It’s possible that the LTO consortium has revised its LTO-10 specification from the published roadmap on its website:
Spectra’s announcement mentions 30 TB raw capacity per cartridge, which is 66.7 percent capacity growth from LTO-9’s 18 TB but it is 6 TB less than expected.
Spectra says that LTO-10’s transfer speed is 400 MBps raw, the same as the prior LTO-9 generation. So far LTO transfer speeds have increased with each generation.
An increase in throughput depends upon the tape drive reading and writing bit area polarity signals to the tape which are smaller with each generation, and also on the tape’s speed through the drive. Having the same transfer rate as LTO-9 is an abrupt change to the previous consistent speed increase with each LTO generation, as our table shows:
Up until now each successive LTO generation has been backwards-compatible with one and sometimes two previous generations. The LTO organization states that: “LTO specifications for backward compatibility up to generation seven of the technology is to write back one generation and read back two generations. The later 8th and 9th generations of LTO Ultrium tape drives are able to write back and read back one generation.”
IBM says nothing about backward compatibility, with its LTO-10 datasheet simply stating: “IBM LTO 10 tape drive can read and write to LTO Ultrium 10 cartridges.” Translation: there may be no backwards compatibility.
So, with LTO-10, we have not gained as much capacity as hoped, are stuck with the same transfer speed as LTO-9, and very possibly have lost backwards compatibility, all without the LTO organization saying anything about it. We have asked SpectraLogic and the LTO organization about these points. Spectra Logic provided responses to them.
Blocks & Files: Why is Spectra saying LTO-10 has a 30TB raw capacity when the LTO roadmap says LTO-10 has 36TB raw capacity?
Spectra Logic: The LTO roadmap has always said that future generations will be “up to” a certain potential capacity. There have been multiple times where the released capacity does not match with the published LTO forward-looking roadmap, at times exceeding the roadmap capacity as we saw during the LTO-7 release, and at times releasing slightly below the roadmap capacity. The actual capacity for each generation is determined by industry demand and the best and most reliable technologies at the time of release. At 30TB of native capacity per cartridge LTO-10 sets a new baseline for capacity, density, and cost effectiveness for the data storage industry.
Blocks & Files: The LTO-10 bandwidth of 400 MBps raw is exactly the same as that of LTO-9. Why has there been no change in throughput?
Spectra Logic: The LTO-10 technology was prioritized for higher capacity. At 400 MBps native throughput tape is still one of the fastest ways to archive large amounts of data, especially when used in large robotic tape libraries where up to 168 drives can be used in parallel for transfer rates of over 67 GBps. In addition, data throughput can reach up to 1000 MBps on SAS and up to 1200 MBps on FC with compression.
Blocks & Files Is the Spectra LTO-10 drive (IBM’s drive) backwards-compatible with LTO-9 or not?
Spectra Logic: LTO-10 has new technologies that provide advancements for reliability, flexibility, and the future of LTO tape drives. With the advancements, LTO-10 (unlike LTO-9) does not require both media optimization and archive unload. However, there is no method to provide backward media compatibility.
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Symply told us that the LTO-10 30 TB raw/75 TB compressed capacity will not rise to the LTO roadmap’s maximum of 36 TB raw/90 TB compressed. It said: “The full-height LTO-10 drive has a performance of 400 MB/sec, the same as LTO-9. There are always inevitably going to be design compromises, the performance of the drive could have been increased but that would have had a knock on effect on capacity and other features. The majority consumers of LTO technology are looking for the highest density in the smallest footprint.”
Regarding backwards compatibility it said: “LTO-10 is not backwards compatible with LTO-9. … the drive is almost a completely new design; ASIC, drive head, media formula and loading mechanism. The biggest challenge in increasing capacity on the media, is backwards compatibility. To enable the capacity on LTO-10 and beyond the technology needed to ‘switch tracks’.”
IBM’s LTO-10 drive offers both two Fiber Channel or SAS ports and one Ethernet port. The dual ports allow daisy-chaining a second FC or SAS device. The drives are available in full height and half height form factors.
Spectra is supporting LTO-10 with its TFinity, T950, T950V, T680, T380, T200, Cube, and Stack models. SAS-equipped models are interoperable with the Spectra OSW-2400 Optical SAS Switch. LTO-10 technology is available for immediate ordering and Spectra will offer LTO-10 media at launch. Customers may add LTO-10 drives to any new Spectra library builds or upgrade existing systems using full-height Fibre Channel or SAS drive options. Initial shipments of LTO-10 drives and Certified Media will begin in June 2025.
Tape library manufacturers Symply and Quantum have also announced LTO-10 support, with Symply saying it will be releasing further news over the next few weeks in the run up to GA of the full-height drives.
It is, by the way, the 25th anniversary of the LTO (Linear Tape Open) technology inception, and it looks to be not advancing as fast these days as in previous generational changes.
Bootnote
The LTO organization replied with its answers:
Q1: The LTO Program is still working on capacity improvements for LTO-10 which could rise beyond the current roadmap. These improvements will be announced in due course.
Q2: The LTO-10 technology was prioritized for higher capacity. At 400 MB/s native throughput tape LTO-10 is still one of the fastest ways to archive large amounts of data, and with compression, data throughput can reach up to 1000MBps on SAS and up to 1200MBps on FC.
Q3: No, LTO-10 does not offer backwards compatibility. LTO-10 drives use new recording technology to enable LTO format improvements in the future. One immediate difference is that unlike LTO-9, LTO-10 media does not require initialization or optimization nor archive unload which should improve the user’s day-to-day experience.
