Managing RAID on Linux

Installing Linux onto a Promise Array

Installation on Promise RAID controllers can be problematic for two reasons. First, most Linux installers detect both the arrays defined (logical disks) and the individual ATA disks, and list both as available, valid installation targets during the system configuration. Thus, disks that are members of arrays might also show up in partitioning utilities. It’s left up to the user to determine which device is the valid array on which to install the Linux operating system.

When working with Promise controllers, it’s important to choose the ataraid driver and not the FastTrak driver. The ataraid driver is open source and was developed by Arjan van de Ven of Red Hat. The FastTrak driver is a binary-only driver and is distributed by Promise. Licensing aside, the main difference between the two drivers is that the Promise driver uses the SCSI subsystem to interface with the Linux kernel. That means Promise’s binary-only driver needs to perform additional steps to translate commands between SCSI and ATA. Conversely, the open source driver uses ATA directly and is consequently faster and more stable.

Tip

If you are using the SuperTrak controller, the same semantics I describe here will apply, but the SuperTrak controller uses a different driver, also available from Promise. The SuperTrak controllers are also reported to work using Linux’s Generic I2O Driver. Your mileage may vary.

When using the FastTrak driver, I experienced many system lockups and slow-downs ...