Now, let the system reboot further until you see the Silicon Image drive detection text below. Press CTRL-S or F4 to enter the RAID utility.
During the boot process, you'll see the Silicon Image controller detecting the two SATA hard disk drives connector to it. It will then prompt you to enter the RAID utility. Press CTRL-S or F4 to enter the RAID setup menu.
Next, you'll need to create a RAID volume. What is RAID? RAID or better known as Redundant Array of Independent Disks, is a method where two or more hard disk drives are combined to form one logical unit. Basically, RAID provides better performance and also data fault tolerance. Performance is achieved through the use of two drives to simultaneously read and write data. As the saying goes, two heads are better than one, and so, two drives doing the same task would result in better performance. Fault tolerance, on the other hand, is achieved by using the other hard disk drive to mirror the contents of the first drive. In other words, you'll always have a backup copy of your data in another drive. If any one of the drive fails, the working copy will take over and your system will continue to run as if nothing happened.
There are basically two levels of RAID achievable by the Silicon Image controller, RAID 0 (striping) and RAID 1 (mirroring).
In RAID 0, or striping, two drives are used to store and access data simultaneously. In other words, a particular file would have parts of it stored in one and the rest in the other drive. As both drives are used to access the file simultaneously, you can expect the I/O performance to increase. In addition, you'll also see your array's capacity doubled (if you have two identical drives). For example, if you installed two 80GB drives, you'll have a total of 160GB in the array. If however, you have one 60GB and one 80GB drive configured for RAID 0, the capacity will be determined by the drive with the lowest capacity, in which case, you'll get only 120GB. The only drawback with RAID 0 is the lack of fault tolerance. If any drive fails, it will affect the entire array and you will lose all your data even if the other drive is still working.
In RAID 1, or mirroring, data written to one drive will be duplicated (or mirrored) on the other drive. If one drive fails, the other drive will continue to function and the system will not crash. However, one of the drive is always used for redundancy and as such, the capacity of the array is equal to the capacity of the smallest drive used in the array. For example, if you have a 60GB and a 40GB drive configured for RAID 1, the resulting capacity of the array would only be 40GB. Ideally, we recommend drives with identical capacities so that none of the extra storage space are wasted.
Now that you know what's RAID, let's carry on with the configuration. In the following steps, we'll teach you how to build a RAID 0 array. You can always follow the same steps to build a RAID 1 array if you want to go for data redundancy rather than performance.
You can perform various functions in the RAID setup menu. Select 'Create RAID set'.
You have two options here - Striped (RAID 0) or Mirrored (RAID 1) array. Select the 'Striped' option for performance.
Select Auto configuration if you want the utility to automatically select the drives for you. Alternatively, you can manually select which drives you want to use in the RAID array. We recommend that you use manual configuration.
You can select the stripe chunk size under the manual configuration option. If you chose auto configuration earlier, it would have defaulted to a chunk size of 16K. Manual configuration would allow you to select the chunk size. We recommend using 64K chunk size.
Chunk size or stripe size is the size of the smallest block defined by the RAID controller. A smaller chunk size would result in smaller bits of files stored in each of the drives. If you anticipate storing files with file sizes in the range of 1KB to 16KB, a small stripe size may help you reduce disk usage. If you have large files (such as video or audio files), larger stripe sizes will help you increase access performance. This is just a simple scenario for illustration purposes although in real-life usage, it can get quite complex. Performance won't vary a lot with chunk sizes especially if you're using it in an environment with varied file sizes. Always go for something in between for a better balance, therefore, we recommend using a 64KB chunk size in your striped array.
Once you're done creating the RAID set, press CTRL-E to exit and reboot. You'll now see the new RAID set displayed here when you reboot the system.
