RAID Levels using different disks?

[Rob_12]

Is it absolutely necessary to have the exact same disk in a mirrored or raid 5 configuration? It seems people have different opinions about this. Some say yes there should be no problem...it would just run at the lower spec. ie. spindle rate, Ultra technologies, disk capacity, etc. Others say it must be the exact same drive.

I have an E60 that is mirrored using the 2 onboard controllers, NT 4.0, and mirrored in Disk Administrator.

The other is an LHPro, 3 drives configured to Raid level 5 using the integrated raid controller. NT 4.0

Thanks

Rob

[Enes Dizdarevic]

Software mirror in NT allows different disks to be mirrored. The size of mirrored volume must be less or equal to the smaller disk in pair. The unused space on bigger disk can be used vor new (unmirored) volume.
When you are talking about hardware raid the answer depends on raid controller. Some raid controllers do not allow using different disks in one raid (for instance old EISA based HPDA - Mylex). Newer netraid adapters (including HP onboard netraid) allows using different disks in one raid but unused space can not be used in any other way.
Of course it is better to use same disks in raid to avoid wasting space but in some situation (for example replacing failed disk in raid with newer one) you are forced to do this.