How much backup space to allocate?

[Comdrpopnfresh]

I currently segregate the data on my win7 desktop into 4 partitions (not counting the 100mb reserve):
OS
Storage
Backup
DVR storage

there are 4 drives:
180gb ssd {100mb, win7}
640gb {storage, backup| 50/50}
1TB {100mb old, 120gb old win7, DVR}
250GB misc

First of all, should I be using windows backup to image/backup just my OS, or the OS + Storage? How large should the total backup space (used + reserved) be in relation to the content?

I've had hiccups using windows backup- likely due to my storage being on the same non system disk as the backup targets. I need an automated backup that succeeds each time. Is it best just to dedicate a disk to backup? How big of a backup space is necessary to cover the 180gb win7 ssd and ~300gb or storage?

 

[ArisVer]

The best you can do if you can afford it, is get another identical hard drive and do a raid.

 

[Cerb]

The best you can do if you can afford it, is get another identical hard drive and do a raid.

No, it's not. If a problem occurs other than drive failure, you will then have an extra drive with bad data.

RAID >0 is for availability, and is not a suitable backup replacement. That is, limited downtime due to drive failure. With a backup, you can accidentally delete files, get a corrupted partition, etc., and not have it be lost. With RAID, you don't get that.

Is it best just to dedicate a disk to backup?

Best? It's the only sane way to do it. At the least, don't have the source and targets on the same disk, even if it should theoretically work. If you're up for spending the money, it's hard to go wrong with Acronis Home, IMO. MS' works, but there's good reason companies out there can make a profit doing fundamentally the same result. MS' can be frustrating, sometimes.

How big of a backup space is necessary to cover the 180gb win7 ssd and ~300gb or storage?

For a backup with only the latest, <500GB. It goes up from there. If buying a drive, 1 and 1.5TB are where it's at. If using what you have, the 640 might be able to handle it, depending (incremental, differential, backup frequency, age of backups you want to keep, etc.).