SoftRAID 3 Manual Excerpts:
Mirror Essentials
SoftRAID’s unique strategy for creating Mirror volumes let’s you
increase the power and flexibility of your backup scenarios. SoftRAID allows more
than two disks in a Mirror volume and its Mirror volumes offer the same high performance
reads as its Stripe volumes with the same number of disks. Mirror volumes can also be used as startup volumes on PowerPC and Intel Macs. This section will give a more detailed explanation of how you create and manage Mirror volumes with SoftRAID.
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Creating a Mirror Volume
1. Select New... This command is located under the Volume menu. The New Volume window will appear:
2. Select the Disks - Disks can be chosen from the New Volume window, or from the Application window before the New.. command is selected. If disks are chosen from the Application window, they will appear highlighted in the New Volume window. Disks can be selected by clicking, shift-clicking, command-clicking, or dragging through the list of disks.
3. Select the Volume type - The Mirror volume type can be chosen from the pull-down menu or by clicking on the icons at the top of the window.
4. Select the File System - Choose HFS Extended unless the application to be used on the volume specifies UFS (Unix File System) in its documentation.
5. Select the Optimization - SoftRAID 3 gives you four choices for optimization: Workstation, Server, Digital Video and Digital Audio. Choose the setting which best describes how you will use the volume. SoftRAID will then adjust transfer and Mirror rebuild parameters for each setting and enable Journaling for the Server setting. If you are unsure of the which setting you need, choose Workstation.
6. Select the Volume Size - This box will, by default, display the Maximum size Mirror volume which you can create with the disks you have selected. Type in the desired volume size. If after selecting a volume size you wish to change to the Maximum size again, use the Max size button.
7. Type in the New volume name - This name will appear in a Volume tile in the Application window and under the Volume icon on the desktop. Volumes names should be less than 28 characters and cannot include colons : or forward slash /.
8. Click the Create Button - The Primary Disk dialog box will appear. The Primary disk contains the original data and the secondary disks are identical copies of it. When you create a new Mirror volume, SoftRAID asks which disk you prefer as your Primary disk and then designates all others in the volume as secondary disks.
SoftRAID always requires one Primary disk in a volume. If SoftRAID does not detect a Primary disk, it will automatically convert one of the volume’s secondary disks into the Primary disk. If a Primary disk fails during Mirror operations, SoftRAID will automatically convert a secondary disk to become the new Primary to ensure the data integrity.
A Mirror Volume and its disks
Adding a System to a Mirror volume
A new or existing SoftRAID Mirror volume can be transformed into a startup volume for PowerPC and Intel Macs by installing Mac OS X on it. You will need to create a modified Mac OS X install CD which contains the SoftRAID driver for a successful installation. The Create Modify Mac OS X Install CD-ROM or DVD command located in the Utilities menu is explained on page 35 of this manual.
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Taking Care of Mirror Volumes
SoftRAID is always taking steps to insure the integrity of a Mirror volume. If all of the Mirror volume disks are not present at startup or if an i/o error occurs in a read or write operation, SoftRAID will change the volume’s state. SoftRAID will also detect when a crash has occurred and take steps to ensure the integrity of your data.
This information will either be reported in the disk and volume tiles in the SoftRAID application or be displayed in a dialog box by the Monitor when the application is not running. The following section will describe the different states that may happen to a Mirror volume and the ways of changing those states.
Volume and Disk States
SoftRAID displays information about the state of volumes and disks in the volume and disk tiles of the Application window. Text in Green indicates that everything is
operational, Red indicates an error state which should be addressed, and Blue indicates procedural information provided by the application.
No errors - This is the optimal state for an operational Mirror volume.
Missing secondary disk - A missing secondary disk state can occur:
At startup - if one or more of the disks in the mirror volumes did not get connected correctly, or did not get turned on correctly, or malfunctioned.
After startup - if one or more of the disks is turned off or disconnected while the volume is in use.
Whenever a Mirror volume is detected, the SoftRAID driver waits for 15 seconds for all disks to appear. This value can be changed in the Driver panel of the Preference dialog if the Mirror volume has disks which take longer to spin up. If after 15 seconds, SoftRAID detects that any disks are missing, it will mount the volume and change the state in the volume tile to missing secondary disk. The Mirror volume can still be used in this state.
This volume state can be cleared in several ways depending on the cause of the missing secondary disk:
- If the missing secondary disk state is the result of a dead disk and the disk is removed and not replaced, the Remove Missing Secondary Disk command in the Volume menu can be used to set the state back to no errors. If it is desirable to keep the Mirror volume with the same number of disks as before, another functioning disk can be added back to the volume with the Add Secondary Disk command under the Volume menu.
- If the missing secondary state is the result of an incorrectly connected secondary disk, the disk may be reconnected and the Mac rebooted if necessary, (FireWire, Fibre Channel and USB do not require rebooting.) If any writes have occurred to the volume while the disk was missing, the volume tile will indicate an out-of-sync state and the disk tile will also indicate out-of-sync. The Rebuild Mirror command is necessary to clear this state as described below. If no i/o requests have been made, the secondary will be added back to the volume and the missing secondary disk state will disappear.
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