Figure 10-11. Add Partition window
If you are using RAID, follow the steps in the next section to create a boot partition.
10.2.1.2. Creating RAID devices
Table 10-1 shows RAID level recommendations for various numbers of disk drives. ( Table 6-3 describes the RAID levels supported by Fedora.)
Table 10-1. RAID recommendations based on the number of same-sized disk drives
| # of disk drives | Possible RAID levels | Recoverable failure | Notes |
|---|---|---|---|
| 1 | Cannot use RAID | None | |
| 2 | RAID 0 | None | Improves performance but also increases the risk of data loss. It provides storage capacity equal to two drives. |
| RAID 1 | 1 drive | Provides storage capacity equal to one drive. This is the only RAID level that can be used for the /boot filesystem. | |
| 3 | RAID 5 | 1 drive | Provides storage capacity equal to two drives. |
| 4 or more | RAID 5 with no hot spares | 1 drive | Provides storage capacity equal to the number of drives minus one. |
| RAID 5 with hot spare(s) | 1 drive at a time to a sequential maximum failure of 1 + the number of hot spares | Provides storage capacity equal to the number of drives minus the number of hot spares minus one. | |
| RAID 6 with no hot spares | 2 drives | Provides storage capacity equal to the number of drives minus two. | |
| 5 or more | RAID 6 with hot spare(s) | 2 drives at a time to a maximum of 2 + the number of hot spares | Provides storage capacity equal to the number of drives minus the number of hot spares minus two. |
To create a RAID array (device), you must first create the partitions that will make up the elements of the array. Start by creating a RAID 1 boot partition of about 100 MB on each drive. Although it's tempting to create a giant RAID partition to use the rest of the space, I recommend that you divide the space on each drive into five partitions of roughly equal size. For example, if you are using 120 GB disk drives, create five partitions of 24 GB; if you are using 10 GB drives, create five partitions of 2 GB. Combine these partitions into five RAID arrays, each incorporating one partition from each drive, and then combine those five RAID arrays into a single volume group. The advantage to this approach is that it enables you to migrate to a different RAID level as long as a minimum of 20 percent of the VG space is free (see Lab 6.1, "Using Logical Volume Management ").
To create a partition to serve as a RAID array element, click the New button in Disk Druid's main window. The Add Partition dialog will appear, as in Figure 10-12 .
Figure 10-12. Adding a RAID partition
Another way to create a RAID partition is by clicking on the RAID button; the dialog in Figure 10-13 will appear, asking what you want to do next. Select the option "Create a software RAID partition" and click OK.
For the File System Type, select "software RAID." Deselect all of the Allowable Drives checkboxes except one to indicate the drive on which you wish to create the partition. Enter the Size in megabytes, and select "Fixed size." Click OK to proceed.
Repeat this process to create partitions for the other elements of the RAID array on other drives. For example, when creating a 2 GB RAID 1 array that spans two drives, create a 2 GB software RAID partition on each of the two drives.
Once you have created all of the partitions for the array, click the RAID button to view the RAID Options window, as shown in Figure 10-13 .
Figure 10-13. RAID Options window
Select the option to "Create a RAID device" and click OK. The Make RAID Device window will appear, as shown in Figure 10-14 .
Figure 10-14. Make RAID Device window
To use this RAID array as a boot filesystem, enter the mount point /boot , set the File System Type to ext3, set the RAID Level to RAID 1, and then select the checkboxes of the RAID partitions that will serve as elements of the array. Click OK to create the filesystem.
When creating a RAID array, use partitions that are exactly or almost exactly the same size because the size of the smallest element defines the amount of space that will be used in each of the elements; any differences between the size of the smallest element and the sizes of each of the other elements is wasted space.
To create a RAID array that will serve as a Physical Volume in an LVM Volume Group, set the File System Type to "Physical volume (LVM)," select the RAID Level, and select the checkboxes of the RAID partitions that will serve as elements of this array. Click OK to create the array.
10.2.1.3. Creating an LVM layout
Whether you're using RAID or not, LVM is the best way to set up partitioning: the overhead is minuscule, and the flexibility that it buys is valuable.
In order to configure LVM during installation, you need to create one or more partitions that will serve as physical volumes. There are two ways to do this:
Use RAID arrays as physical volumes, following the instructions in the previous section.
Use disk partitions as physical volumes. Click New in the Disk Druid main screen to access the Add Partition window ( Figure 10-11 ). Select "Physical volume (LVM)" for the File System Type, enter the partition size, and then click OK to create the partition.
It usually doesn't make sense to combine RAID and disk partition PVs in the same volume group because you will lose the data protection provided by the RAID array.
Once you have created the physical volumes, click the LVM button. The window shown in Figure 10-15 will be displayed.
Figure 10-15. Make LVM Volume Group window
Enter a descriptive volume group name, such as main for your primary volume group. The default physical extent size is 32 MB, which is a reasonable choice for most applications. If you have a good reason to use a different extent size, set it now because it cannot be easily changed after installation.