On Wed, 13 Jun 2012, Roger Deschner wrote:
>[...]
> BTW, mounting LTO4 tapes in LTO5 drives is supposed to work, and most of
> the time it does. However, we have experienced a much higher I/O error
> rate when LTO4 tapes are mounted in LTO5 drives, compared to mounting
> the same LTO4 tapes in LTO4 drives. (All drives are HP.) [...]
>[...]

Somewhat better experiences over here with IBM drives:

While we have been plagued by many spurious "LOCATE" errors for almost a year,
with both LTO4 and LTO5 drives, and any LTO3/4/5 media, a few weeks ago IBM
finally released firmware versions ("BBH8" for LTO4, "BBNN" for LTO5 drives)
that cures (again - at least on LTO4) that problem.
For the last few weeks, we've seen ZERO drive/media-related (as opposed to
apparently SAN-related) errors.

Admittedly, it does happen that a drive goes bad now and then.
(Also, we've seen >> 0 (FUJIFILM) LTO5 media that proved DOA
at time of labeling or first use).

Never found a compatibility problem with LTO3/LTO4 media in LTO4/LTO5 drives,
however we didn't try to read LTO3 media in LTO5 drives.


Statistics ...

Drives: 13 x LTO4, 24 x LTO5 in 2 Quantum (originally ADIC) Libraries
        [so far using a home-grown "external library manager"].

Total Tape Mounts: ~750 / day (~9 noticeable [V5 :-] server instances,
                   all using group collocation)

Backup volume: >~ 15 TB (decimal ;-) / day, plus lately, a few TB
               of NDMP backups that DON'T appear in the "dsmaccnt" file
               [which reminds me of the urgent need to start collecting
               pertinent statistics from elsewhere :-]


((Please notify me of your questions & opinions by e-mail -
  I no longer find the time to regularly scan all of ADSM-L)).

Best regards,

        Wolfgang J. Moeller <moeller AT gwdg DOT de>

Tel. +49 551 201-1516 ... not representing ... GWDG, Goettingen, Germany