How to manage a big itunes library?

Ejlif,
I feel your pain. I had 40,000 songs on a hd that failed me a month ago. I didn't have it backed up so all was lost.
I found that i didn't listen to a lot of what was on there. I did have to re-rip a bunch of cd's but i only put on there what i actually want to hear. Makes it easier to find what i really like to listen too.
I haven't bought a cd in a long ,long time. I grew tired of buying a $14 cd for one or two songs. I end up surfing itunes and buying music there. I know it's lower quality but i would rather listen to good music poorly recorded than the other way around. Sorry for the rant!

If you want a more seamless backup you may want to consider one of the less expensive RAID solutions that use very simple interfaces. In this scenario you would have a slightly larger RAID unit as your primary music library. The RAID unit contains several raw hard drives which easily slide in and out of the unit. The hardware / software can make one or more of those drives a 'redundant' backup of the main drive, and continually back it up as the main drive grows (within the capacities of the enclosed drives of course). In the event of a drive failure, which is inevitable with any drive, you'd simply slide out the failed drive and slide in a new one. The RAID system should never miss a beat and would immediately put the backup into use should the main fail, and would immediately backup to the drive you slide in to replace the failed drive. At best it is a constant ongoing process. Drawbacks are the larger size, more noise (not an issue if you are using a WIFI solution), and greater initial expense (one of the current crop of affordable RAID solutions may run around $800 initially, but then you only will have to replace raw hard drives (cheap). Another suggestion would be to buy the slightly more expensive and longer-lasting drives like G-Tech, but that doesn't mean they'll necessarily never fail - all drives will eventually fail. In general the larger TB drives are less reliable overall than the moderate drives. 500GB is my flavor of choice. TB drives are more often two or more 500's in a case together. They make more noise, are slower read/write, and are more prone to early failures in general. A quick read of any real-world reviews should prove that out. Not to say that there are not exceptions.

Good luck.

One other suggestion is consider adding hard drive coolers to each drive. These are fan-based coolers that mount directly on the drive. I picked up 4 recently for my systems; they were $5 each. They went on quickly and lowered the hard drive temp of every drive by 10 to 15 degrees centigrade. Since heat speeds up the failure process it is not a bad idea (though it does not replace backups.)