We currently have two 3494 libraries with 6 3590-H drives in each that have
each been paid for and depreciated and are still working well for the most
part.  One of the libraries is offsite but accessible via dark fiber we own
and is setup as a copy storage pool for DR. We are looking into upgrading
the tape components of our TSM system to two libraries with 4 LTO-4 drives
in each because the speed and capacity difference with LTO-4 drives is so
much larger than the 3494 library. We will also save lots of floor space as
newer libraries are a fraction of the size of the 3494s we have that
currently have 7 frames each. The 3494 is partitioned so that part is for
TSM and part for the mainframe but when this is all said and done, the
mainframe will be going away so a newer tape library will only be used for
open systems. So far we have talked to several vendors about their products
including: IBM,STK and EMC and have even looked at some third party vendors
like Overland.  Right now everything is open to suggestion but we are
severely budget challenged. Some of the questions I'm looking for advice
about are:

If we currently have 6 3590-h drives in the 3494 library, do you think can
we get by with 4 LTO-4 drives in the new libraries given that speed and
storage capacity is so much better with LTO-4 drives? Most of the tape
activity is backups only. Occasionally we have a file restore or two.

We are hoping to keep the new tape library for 5+ years so reliability is a
big factor.  Any LTO-4 libraries more reliable than others? Do tapes last 5
years?

Any advice or ideas are very welcome as everything is undecided right now.

John