Deploying Suse Linux Enterprise Server
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Installing Suse Linux Enterprise Server
Creating a Software RAID Array
The biggest difference between setting up a Software RAID solution as opposed to a Hardware RAID solution is the fact that a Hardware RAID adapter will present the Array as a single drive to the Operating System. A Software RAID solution must have all of it's drives partitioned and configured within the Operating System. Thankfully, Suse Linux Enterprise Server provides excellent tools to create and maintain a Software RAID solution.
The first step in creating a Software RAID Array is to create partitions that will be part of the array. This is a little different than a Hardware RAID solution, which uses entire drives for it's arrays. The process of creating these partitions is similar to creating any partition, except you do not format the partition, instead you "identify" the partition as being "0xFD Linux RAID".
In the example I am giving here (see image below), I will create a single partition on every drive that completely fills each drive. In a real system, it is common practice to separate out different RAID partitions on each drive. For instance, most systems that deploy a Software RAID solution will have a separately mounted /boot filesystem that could very well be on it's own Software RAID Array. The SWAP partition could also be created on a similar Software Array.
Note: When creating software RAID arrays, do not use two Linux RAID partitions from the same disk in one array as this would nullify most of the benefits of using a RAID solution. Also, when selecting disks to use for software RAID, if you use ATAPI disks ensure that you only use one disk per controller. For instance, do not put 2 disks (one "Master" and one "Slave") on a single controller as this would dramatically reduce the performance of the RAID array (this would also substantially increase the time it would take to rebuild the array).
Creating Linux RAID Partitions and selecting the Software RAID Type
Once you create all of the Linux RAID Partitions you need, the next step is to actually create the Software RAID Array. To do this, you click on the RAID drop-down button, then select "Create RAID". The installation procedure (or the Yast Partition Module if you are doing this after installation) will then start the RAID Wizard.
The first step in the RAID Wizard is to select the type of RAID level you want to implement. (See the previous section for information on RAID levels, but remember that RAID level 0 does not provide any data redundancy and if a drive fails in a RAID 0 Array the data in that array would be lost.) After you select the RAID level, the next step is where you select which "Linux RAID" partitions that you want to include within this RAID array.
Adding "Linux RAID" Partitions to the RAID Array and Initializing the Array
The next step is where you actually create the array. Here is where you have a few choices to make. The first of which is to select the format. If you are going to use this RAID array with LVM (Logical Volume Management - which is covered later), then you would select "Do not format" and remove the "Mount Point". If you are not going to use LVM, you would simply select format type and set the mount point of the array.
The next decision you have is what "Chunk Size" to set for the array. The chunk size is actually the size of the smallest "chunk" of data that you will write to a particular disk. For instance if you have a file of 64kb and the chunk size of the array is 8kb, there will be eight 8kb "chunks" written across the array.
The value of the Chunk Size is very dependent on not only the RAID type, but also on the filesystem used on the RAID array. There is not a 100% exact perfect chunk size for every hardware setup and situation, but there are good guidelines to start from. A good rule of thumb is to start with 32kb chunks sizes for RAID 0 arrays and 128kb for RAID 5 arrays. With RAID 1 arrays, the chunk size really only pertains to how data is read from the array, so a good start would probably be 4kb. For RAID arrays that you are going to use as Swap, 64kb is the best. Remember these are only starting points, to fine tune your setup you really should test different sizes to find what is optimal for your configuration.
Once everything is configured, click Finish to create the array.
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