Bit off topic but does anyone have any experiences of migrating from LTO3 to 4 or 5 technologies, do you literally get double the storage each jump along with speed? I'll take speed with a pinch of salt based on what you can throw at it 
I'm obviously after real world experience rather than white papers and perfrect test lab scenarios.
I went from LTO2 (IBM) to LTO4 (HP). My gut feeling is the IBM drives got somewhat higher compression. I no longer have any LTO2 stats but here is some observations from my current LTO4 tapes. I have just over 200 tapes. All backups are to staging then (de)staged to tape. I have two retentions – two weeks for incrementals and 6 weeks for fulls. All used tapes are removed each weekday and taken “offsite” – some are not full. Quite a few of the backups are multi-terabyte. I know from watching iostat that some sections of some servers compress well and some do not compress (in one case I have several terabytes of jpg’s).
Sorting Media and Device Management/Media/Volume Pools/NetBackup by “Kilobytes” I see on the high end 40 Full tapes with 1.1TB to 1.8TB but 2 tape are listed as Active with 1.6TB and 1.5TB. On the low end there are 21 Full tapes with .45TB to .64TB (this of course seems odd as LTO4 should contain at least 800GB).
Have seem tapes with just over 3TB but not today.
Anyone know if a tape is passed over because only large images remain to destage is set to “Full”? I have not observed this but with so many tapes marked Full with less than 600GB seems fishy to me.
Hope this helps,
GlenG
I have orca stats on my two LTO4's here is graph of throughput over the last about 18 hours (this is total of two drives):
This is the percent busy:
have a good day,
GlenG
what is your main aim behind upgrade ?? is it speed or size ?
you will get both higher in LTO4 & LTO5.
do remember there is no SCSI connectivity in LTO5 (only FC & SAS is available).
so you need to pay few more $ 
Bear in mind that if you have old LTO2 tapes that LTO5 will not be able to read them so you may need to keep an LTO3 drive for restores.
Generally you can read two versions earlier and write to 1 version earlier.
So LTO4 can read LTO3 and LTO2 and also write to LTO3 but cannot write to LTO2.
ONLY migrate to new technology if you are 100% sure that the tape drive is the bottleneck. If you are currently seeing less than 100 Mb/sec on your LTO3's, you don't need new tape drives.
Use info in the Performance Tuning Guide to 'chase the bottleneck'. this will include read speed on client's disk, network transfer, media server capabilities, etc....
