Primer: 3Ware 9xxx raid cards
3ware 9xxx cards have a finite number of ports, typically, 8, 12, or 16. Each port may have:
- One drive attached
- No drive attached
If a drive is attached, it may be:
- Part of a raid unit (u0, u1, u2, etc.)
- A hotspare spare to a raid unit
- Exposed through the 3ware card (JBOD)
When drives are assigned to a unit, that unit will have a total of X GB of storage where N is the number of drives and S is the size of the smallest drive:
- RAID 0: X = S * N
- RAID 1: X = S
- RAID 5: X = S * ( N - 1 )
- RAID 6: X = S * ( N - 2 )
The space of one RAID unit may be used for:
- One storage volume
- One boot volume and one storage volume
The single storage volume is most common. Having a seperate boot volume is only necessary if:
- You are booting off of that Unit (u0, u1, u2, etc.)
- The total storage provided by that unit (X above) is greater than 2TB.
Volumes in excess of 2TB must have a GPT disk label, and GPT labeled disks aren't bootable. If you have a RAID array that exceeds 2TB we will create a smaller boot volume to overcome this limitation.
Each volume will appear to the OS as another "hard disk" in that it will have its own device name under /dev (/dev/sda, /dev/sdb,/dev/sdc). Do not confuse volumes in the 3ware configuration with partitions or LVM in the OS. The OS can not tell a boot volume and storage volume are part of the same unit. 3ware volumes have nothing to do with the Logical Volume Manager.
Last Updated on Tuesday, 05 August 2008 16:27