Working with RAID Groups

Working with RAID Groups
	Chapter 2. Configuring a NearStore VTL Appliance

RAID groups are constructed from the NearStore VTL-attached physical disks, and provide a virtualization layer between the physical disks and the virtual tapes. This layer lets you add, remove, and replace the physical disks without affecting the structure of the virtual tapes or the data stored on the tapes.

The remainder of this section provides information on viewing, adding, and dropping RAID groups from the NearStore VTL.

This subsection contains the following tasks:

Listing RAID Groups

The NearStore VTL displays all disks that have been added to its configuration on the RAID Group List screen. Simply connecting a disk to the NearStore VTL does not add it to the configuration of the system. You must first connect the disk, as specified in the NearStore VTL Installation and Setup Instructions, and then you must add the disk to the configuration of the system. See the section called “Creating RAID Groups” for more information on adding RAID groups to the configuration.

From the Configuration Tasks menu, located on the left side of the screen, click the RAID Groups task category.

The initial screen has the Shelf View radio button selected and shows an iconic view of the RAID groups. Placing the mouse over the disk icons shows the information also available in the List View. To change to List View, select the List View radio button.

The RAID Group List screen appears and the following is displayed for each disk that has been added to the system.

RAID Group Name—lists the name of the RAID group.

Storage Pool—(only displays if the advanced option Use Storage Pools is set) lists the storage pool used for the RAID group.

Capacity—lists the capacity of the RAID group.

Capacity Used—gives the amount of disk space currently in use.

RAID Group Status—lists the disk status.

Selecting the Show Detailed button when in List View, adds information on the physical disks used in the RAID groups:

Port Name—lists the port through which the physical disk is accessed.

Shelf—lists the shelf in which the physical disks are located.

Bay—lists the bay within the shelf for the physical disk.

Serial Number—lists the serial number of each physical disk.

Creating RAID Groups

When you create a physical disk, the NearStore VTL labels and includes the disk in its configuration. This means that a NearStore VTL can write virtual tape data to the disk. (NearStore VTL disks contain self-describing data, which can be used to import the disks from another NearStore VTL appliance for disaster recovery purposes.)

Complete this task to add RAID groups to a NearStore VTL appliance:

From the Configuration Tasks menu, located on the left side of the screen, click the RAID Groups task category.
Click the Create RAID Group tab, located in the upper portion of the screen.

The Create RAID Group screen appears, and the NearStore VTL displays the disks that have been connected to it but are not yet assigned to RAID groups.

If you have added disks to the system since the last power cycle, click Discover. The NearStore VTL appliance scans for any physical disks that are connected to it.
If you want to let the VTL assign the name, leave the RAID Group Name field set to Auto Assign; otherwise, type in the name you want assigned to the RAID group.
If Use Storage Pools is set under the advanced options, you can use the Storage Pool Name drop-down list to select the storage pool from which the disks will be assigned.
Decide whether you want to select individual disks or have the VTL automatically assign all available disks to RAID groups. Typically, allowing the VTL to automatically assign disks results in the best possible assignment of physical disks to RAID groups. If you want to have the VTL automatically assign disks, click Automatically Create RAID Groups. Skip the remainder of the steps. If you want to select the disks, continue with step 6.
Select the disks to include in the raid group by clicking in the check box next to RAID Group Storage Pool Name field. You can select all disk by clicking in the check box at the top of the column.
Click Apply (clicking Reset removes your disk selections).

The NearStore VTL displays each disk that you successfully add to the system on the RAID Group List screen.

Setting a Disk to Failed Status

When you no longer need a disk or if you have a disk that is not functioning properly, you fail it from the system. (Note that if the disk actually fails, VTL automatically replaces it from the hot spares pool, and notifies you.) When you fail a disk, the NearStore VTL drops the disk and removes the NearStore VTL label. This means that once you have dropped a disk, you will not be able to access any virtual tapes that it might contain. For this reason export any virtual tapes that are on a disk before you drop it. Exporting the virtual tapes ensures that the corresponding physical tapes have the most-recent data on them.

See the section called “Changing the Export Status of a Virtual Tape” for more information.

Complete this task to fail RAID groups from a NearStore VTL appliance:

From the Configuration Tasks menu, located on the left side of the screen, click the RAID Group task category.
Click the Fail Physical Disk tab, located in the upper portion of the screen.

The Fail Physical Disk screen appears, and the NearStore VTL displays the disks that have been added to it.
From the Action field of the disk that you want to drop, click Fail.

Caution

When you fail a disk, all of the data on that disk is lost.

The NearStore VTL fails the disk and no longer displays it on either the Fail Physical Disk or the RAID Groups List screens.

Importing RAID Groups

In the unlikely event that a NearStore VTL appliance fails, you can disconnect its back-end disks and then import both the configuration of the system and the user data (virtual tapes) into a new system. Restoring both the configuration and the user data to a new system is relatively simple because both the configuration of the old system and the user data are stored on the back-end disks that you are importing.

Note

Configuration data must be manually saved.

Note

Since user data is self-describing, the NearStore VTL does not actually have to retrieve all of the data from disk during a disk import. This enables the NearStore VTL to complete a disk import in a relatively short period of time.

The NearStore VTL has a feature that periodically auto-saves the configuration of the system to the back-end disks. These are the same disks on which the NearStore VTL saves user data. This means that you can load the auto-saved configuration from the back-end disks before you import the virtual tapes (user data).

Caution

Keep in mind, however, that when you import the configuration from a source to a destination system, the configuration of the destination system is overwritten.

In cases where you want to import the user data to a new system without overwriting the existing configuration, do not import the configuration of the source system. See the section called “Managing the Appliance Configuration” for more information.

Complete this task to import a RAID group into a NearStore VTL appliance.

(Optional) Import the configuration of the source system from the disk.

See the section called “Managing the Appliance Configuration” for more information on importing a configuration file from disk.
From the Configuration Tasks menu, located on the left side of the screen, click the RAID Groups task category.
Click the Import RAID Group tab located in the upper portion of the screen.

The Import RAID Group screen appears, and the NearStore VTL displays the following:

Import—use to select the RAID groups to import. Click in the check box to select a group.

Appliance—lists the identification of the system from which you import the disk. This is the name of the system that originally wrote the data to the disk that you are importing. You can also think of it as the name of the system that labeled the disk.

RAID Group Name—gives the RAID group name after importation. Leave this field to Auto Assign to have the appliance assign the name, or fill in a name.

RAID Group Uuid—lists the UUID of the group.

Status—provides the status of the RAID group; for example, whether all of the disks are available.

Shelf—lists the shelf containing the physical disks.

Bay—lists the bay within the shelf containing the physical disks.

Serial Number—provides serial numbers for the physical disks.
Select the RAID group to import. If a RAID group Import check box is gray, the group is not ready to be imported; for example, some of the disks might be missing.
Click Apply to begin the process of importing the selected disks.

The NearStore VTL begins importing the disks into the system.
To view the status of the import operation, click To view the list of importing RAID groups click here to view.

The Importing Physical Disk List screen appears and the NearStore VTL displays the following:

RAID Group Name—lists the RAID group name of the disk.

Status—provides the import status of the disk, including Scanning and Scan Complete.

Dropping RAID Groups

When you no longer need a RAID group or if you have a disk that is not functioning properly, you can drop it from the system. When a NearStore VTL drops a disk, it removes the NearStore VTL label. This means that once you have dropped a disk, you will not be able to access any virtual tapes that it might contain.

For this reason export any virtual tapes that are on a disk before you drop it. Exporting the virtual tapes ensures that the corresponding physical tapes have the most-recent data on them.

See the section called “Changing the Export Status of a Virtual Tape” for more information.

Complete this task to drop RAID groups from a NearStore VTL appliance:

From the Configuration Tasks menu, located on the left side of the screen, click the RAID Group task category.
Click the Drop RAID Group tab, located in the upper portion of the screen.

The Drop RAID Group screen appears, and the NearStore VTL displays the disks that have been added to it.
From the Action field of the disk that you want to drop, click Drop.

Caution

When you drop a physical disk, all of the data on that disk is lost.

The NearStore VTL drops the disk and no longer displays it on either the Drop RAID Groups or the RAID Group List screens.

Managing Hot Spares

A NearStore VTL manages a pool of disks reserved to replace failed disks—this is the hot spare pool. When the VTL detects a disk failure or you manually mark a disk as failed

The failed disk is removed from the RAID group
A disk from the hot spare pool is added to the RAID group
A repair process is started to rebuild the that RAID group

When the VTL automatically builds RAID groups, it assigns appropriate numbers of disks to the hot spare pool. However, you might want to add or remove disks from the hot spare pool either because your application requires more or fewer hot spares, or because you have added or removed disks from the system.

Note

If there are no spares in the spares pool, an action request is generated.

Adding Hot Spares

Complete this task to add disks to the hot spares pool.

From the Configuration Tasks menu, located on the left side of the screen, click the RAID Group task category.
Click the Hot Spare Disks tab, located in the upper portion of the screen.

The Hot Spare Disks screen appears, and the NearStore VTL displays the disks assigned to the pool.
Click Add Hot Spare Disk to display the Add Hot Spare Disk task screen.
(Optional) If you are using multiple storage pools, use the pull-down list to select the name of the storage pool for the added hot spare.
Select Add in the Action field for each disk you want added to the hot spare pool.
Click Apply to add the selected disks to the hot spare pool.

Removing Hot Spares

Complete this task to remove disks from the hot spare pool:

From the Configuration Tasks menu, located on the left side of the screen, click the RAID Group task category.
Click the Hot Spare Disks tab, located in the upper portion of the screen.

The Hot Spare Disks screen appears, and the NearStore VTL displays the disks assigned to the pool.
Click Delete Hot Spare Disk to display the Delete Hot Spare Disk task screen.
Select Drop in the Storage Pool field for each disk you want removed from the hot spare pool.


Working with Virtual Tapes		Working with Physical Tape Devices