Chapter 9. Administration - Logical Tab

9.1 Logical tab

The Logical tab (Figure 9-1) shows the organization of the storage subsystem by logical

drives, arrays, free capacity nodes, and any unconfigured capacity for the storage subsystem.

This tab is divided into two panes: the Logical pane on the left and the Properties pane on the

right. The Logical pane provides a view of the logical components in the storage subsystem in

a tree structure. The Properties pane displays detailed information about the component that

is selected in the Logical pane.

Note: The Properties pane is not used for any configuration tasks. It just shows properties

of selected objects in the same form as it is in the subsystem profile. You can find more

information about the profile in 14.3, “View Storage Subsystem Profile” on page 338.



Figure 9-1 Logical tab



The first line in the Properties pane is the View Associated Components link. When

selected, it opens a window with the physical components belonging to the selected logical

object in the left Logical pane. The associated components are marked by blue bullets in this

window.



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If the first line of Logical pane (Storage Subsystem) is selected, the link opens a window with

Subsystem Storage profile. As usual, you can also get required information from menus, tabs,

and icons in DS Storage Manager.

Your options to configure the storage subsystem depend on the object selected in the Logical

pane. All configuration options are shown as a menu when you right-click a particular object.

We have split this chapter into four basic sections to explain the following configuration

options:

9.2, “Working with unconfigured capacity” on page 222

9.3, “Working with arrays” on page 225

9.4, “Working with Free Capacity” on page 232

9.5, “Working with logical drives” on page 237

The first line in the Logical pane (the root of the logical directory tree) is Storage Subsystem

(already selected in Figure 9-1 on page 220). The name of subsystem and basic status

(green - Optimal, or red - Needs Attention) of this managed subsystem is shown there. In the

right Properties pane you can see overall information about the whole DS3500 Storage

Subsystem.

Right-click the Storage Subsystem in the left pane and a full list of possible configurations

opens in menu as shown in Figure 9-2. The first menu item is Copy Manager. Click it and a

new window opens that lists the VolumeCopy pairs. You can find all details about

VolumeCopy, Copy Manger, and more copy services information in IBM Midrange System

Storage Copy Services Guide, SG24-7822. All other menu items are the same as when you

click the Storage Subsystem menu in pull-down menu bar of DS Storage Manger. This menu

is described in 8.2.1, “Storage Subsystem Menu” on page 189.



Figure 9-2 Storage Subsystem menu



Several other objects in the left Logical pane include:

Unconfigured capacity

Array

Free capacity

Standard Logical Drive

Special Logical Drive (FlashCopy, FlashCopy Repository, Mirror Repository, and so on)



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In the following sections we will describe most of them. others are described in chapters or

sections dedicated to specific topics.



9.2 Working with unconfigured capacity

If you get a new DS3500 subsystem, it probably has all unconfigured capacity. As you start to

configure physical disk drives into Logical arrays, this unconfigured capacity will decrease.

When the whole subsystem is configured and no disks remains, this object disappears from

the Logical pane.

The main task that can be performed on the unconfigured capacity is to create an array. In

Figure 9-3, you can see an example of a partially configured DS3524 Storage Subsystem,

where about 7 TB unconfigured capacity still remains.



Figure 9-3 Unconfigured Capacity example



9.2.1 View Associated Physical Components

Select unconfigured capacity and in the Properties pane on the right side, you can see the list

of associated disk drives that are not configured yet. The View Associated Physical

Components link can also be used to open a window where the unconfigured disks are

placed (see Figure 9-4 on page 223 for an example).

The same window opens if you right-click the Unconfigured Capacity and select View

Associated Physical Components.



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Figure 9-4 Unconfigured Disks



The disks marked with the blue bullets are unconfigured. You can also recognize this by the

icon for unused disks.

Right-click the Unconfigured Capacity in the Logical pane, and start configuring an array by

selecting Create Array.

If you can create a logical drive directly from Unconfigured Capacity (see the menu in

Figure 9-3 on page 222), then you must create an array by first choosing the RAID type, disk

drives, and so on, and then continue with the logical drive configuration process. If an array is

not created, you can still create a logical drive, but the Storage Manager will direct you to

create the array first.



9.2.2 Create array

The example that follows assumes that there is unconfigured capacity on the DS3500 storage

subsystem. This procedure illustrates the most common steps to follow in setting up an array

from unconfigured drives. We first start with the creation of an empty array, and then the

logical drive creation is described in 9.4.1, “Create logical drive” on page 233.

Perform the following steps to create an array:

1. In the Logical pane (Figure 9-5), right-click the Total Unconfigured Capacity and select

Create Array.



Figure 9-5 Create Array from Unconfigured Capacity



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This action starts the wizard for creating the array. The first window of the wizard is an

introduction to the process. It displays the available unconfigured capacity. Read the

introduction and then click Next to proceed.

2. In the Create Array window, type a meaningful array name that describes your set of disks,

and then select either Automatic mode or Manual mode. Automatic mode is the default

option as shown in Figure 9-6. By selecting the Automatic option, the Storage Manager

software selects a combination of available drives to optimize performance and availability,

and attempts to select physical drives from separate enclosures to provide enclosure

protection whenever possible. If some SED disk drives are used in DS3500, you will also

see the check box for selecting the encrypted disks for array creation. For more

information about disk encryption, refer to Chapter 15, “Disk Security with Full Disk

Encryption drives” on page 439.



Figure 9-6 Create Array and assign a name and mode



The Automatic (Recommended) creation of the array selects the drives in the following

order:

– Same capacity-same speed enclosure redundancy

– Same capacity-mixed speed enclosure redundancy

– Same capacity-same speed no enclosure redundancy

– Same capacity-mixed speed no enclosure redundancy

– Mixed capacity-same or mixed speed-no enclosure redundancy

In the Manual (Advanced) mode, you have to select all the drives individually. Make sure

that you select them to maximize performance and availability.

You can also perform manual selection from the Physical tab. You can select multiple

unconfigured disk drives in Physical pane using the Ctrl key before selecting to create a

new array. If you right-click one of preselected disks and select Create Array, the same

initiation window will open as shown in Figure 9-6. In this window you can see manual

mode is preselected. With this manual mode, follow the instructions in this chapter, and

when you reach the window for disk drives selection, you will recognize, your planned

disks are already selected for new array.

3. Click Next to select the RAID level.

– Select the desired RAID level. The window shown in Figure 9-7 on page 225 now

displays the capacity options depending on the unconfigured drives available in your

subsystem. If you have different disk sizes, you have more than one option for the

same number of disks. See Chapter 3, “IBM System Storage DS3500 Storage System

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planning tasks” on page 29 to determine the best RAID level for your specific

environment and application.

– Select the line with required capacity in the list and click Finish. In our example

(Figure 9-7), we create a RAID1 array with two 15kRPM SAS drives.



Figure 9-7 RAID level and capacity



4. The Array Success window (Figure 9-8) appears and confirms that the array is now

created. You can click Yes to continue with the creation of a logical drive (see 9.4.1,

“Create logical drive” on page 233). Select No to finish for now.



Figure 9-8 Array Created



5. Your empty array is created immediately because it does not need to format any logical

drive capacity. You can repeat the same process for creating another array.



9.3 Working with arrays

The array (sometimes referenced also as Disk Group) is a set of disks with a defined RAID

level. You can configure one or more logical drives on it. Available capacity of the array is

displayed in the Logical pane as Free Capacity. If no logical drives are configured, the free

capacity displayed is also total capacity of the array.



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Actions that you can perform on the array can be accessed by right-clicking the array and

selecting from the menu (Figure 9-9).

These options are described in the following sections:

9.3.1, “Locate and View Associated Components” on page 226

9.3.2, “Change Ownership and RAID level” on page 227

9.3.3, “Add Free Capacity (Drive)” on page 230

9.3.4, “Secure Drive” on page 231

9.3.5, “Delete and Rename” on page 231

9.3.6, “Replace Drive” on page 232



Note: Because an array can be created from only from Unconfigured Capacity, the Create

option in the Array menu is never active in this tab.



Figure 9-9 Array menu



9.3.1 Locate and View Associated Components

Select Locate to find the disk drives in the rack from which the array is configured. The

orange LED diodes on these disks blink.

Select View Associated Physical Components to see them in window as shown in

Figure 9-10 on page 227. The disks marked by blue bullets are members of the selected

array. The blue bullet can mark also one or both controllers, if the logical drives are owned by

both controllers.



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Figure 9-10 Associated components for array



9.3.2 Change Ownership and RAID level

In this section we discuss changing the controller ownership and the RAID level.



Ownership

Click Change  Ownership/Preferred Path  Controller A/B to change the logical drive

controller ownership of all logical drives in the array to one selected controller. You can be

sure about multipath drivers and redundant paths in your environment. The change of

controller ownership must be confirmed as shown in Figure 9-11 on page 228.



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Figure 9-11 Change Ownership confirmation



RAID level

Changing the RAID level of an array is performed in a non disruptive manner. This feature is

called Dynamic RAID Migration (DRM). The system remains fully operational while the

process takes place. You might want to perform this operation for the following reasons:

The storage requirements changed over time and existing RAID levels are no longer

optimal for a particular environment.

The performance tuning process indicates that a different RAID level is more appropriate

than the existing one.

It is possible to change any RAID level depending on the following restrictions that apply to

the new arrays:

RAID 1 or 10 requires an even number of disk drives.

RAID 3 and 5 require at least three drives.

RAID 6 requires at least five drives.

There is a limit of 30 drives per array for RAID 3, 5, and 6 arrays.

There are also other limitations when there is not enough free space in the array. For

example, a RAID 5 array of four disk drives with no free space cannot be migrated directly to

RAID 1. If this migration is attempted, an error message will be displayed stating that there is

not enough free space. There must be enough free capacity to change the RAID level. Also, if

the array has an odd number of drives and a migration to RAID 1 is required, a disk must be

added to the array prior to performing the procedure.

When changing from RAID 1 to RAID 5, free space in the array can be gained that can be

used to define new logical drives or expand existing ones.

When the procedure starts, it reorganizes the data segments in the array according to the

new RAID level, and a large amount of I/O happens, so there will be an impact on

performance while the migration happens. The performance impact can be controlled to a

certain extent by changing the value of the modification priority. This parameter is set on a

logical drive basis, and it can be changed for one logical drive, for a set of them, or for all

logical drives in the array. See 9.5.1, “Change Modification Priority” on page 239 for more

details.

Changing the modification priority to a low value during the migration process minimizes

performance degradation. When the migration finishes, the value can be increased to reduce

the time for a rebuild in case of a drive failure. This minimizes the critical time of

non-redundant operation caused by a disk drive fault.

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Attention: After the migration starts, it cannot be stopped. During the migration process,

the array cannot be deleted, logical drives cannot be deleted, and new logical drives

cannot be created in the migrated array.

Certain configuration changes that do not change data structures on the array can be

performed on logical drives during the migration process. These configuration changes

include changing the modification priority, logical drive controller ownership, name change.

Also the its possible to define the mappings during RAID level migration.



Note: Even though RAID migration is a non-disruptive process, carry out this migration

when I/O activity is at a minimum.

To change the RAID level, right-click the array and select Change  RAID Level  n as in

Figure 9-12. The current RAID level is marked by black bullet, and you can select your new

RAID level.



Figure 9-12 Change RAID level menu



The process of RAID level migration is non-disruptive and no redundancy is lost, but it can

take a long time. A warning as shown in Figure 9-13 appears.



Figure 9-13 RAID level change confirmation



If you confirm, the process is started and cannot be stopped. All the logical drives of the array

in the Logical pane tree are marked with clock icon. You cannot do certain other configuration

changes on the array and logical drives until the process is completed.



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9.3.3 Add Free Capacity (Drive)

In today’s IT environment, the need for storage space grows constantly. Because it is

essential that this process be non-disruptive and not cause any downtime, the ability to

increase the available free capacity in an array without needing to restart the host system is

an important feature. This feature is called Dynamic Capacity Expansion (DCE).

With DS Storage Manager, it is possible to add new disk drives to the storage subsystem and

start the expansion procedure while the system remains fully operational. After the procedure

starts, it cannot be stopped. This procedure might have a performance impact because the

expansion process competes with normal disk access. When possible, this type of activity

should be performed when I/O activity is at a minimum. The new free capacity can be used to

create additional logical drives. Existing logical drives in the array do not increase in size as a

result of this operation. Logical drive increasing is called Dynamic Volume Expansion (DVE),

and is described in chapter 9.5.7, “Increase Capacity” on page 251.

Note: Storage Manager supports RAID 0 and 1 arrays with more than 30 drives. In certain

DS3500 storage subsystem configurations, this can improve performance, provided that

the system is optimally tuned. It also improves the data capacities of these arrays. RAID 1

or 10 requires an even number of disk drives.



Attention: It is still not possible to use more than 30 drives in RAID 3, 5, and 6 arrays. After

the maximum number of drives is reached, you cannot add new drives.

To add new drives into an array, right-click the array and select Add Free Capacity (Drives).

In the Add Drives window (Figure 9-14), select one or two drives to be added to the array,

depending on whether RAID 1 or 10 is being used by the array. The controller firmware

enables a maximum of two drives to be added at one time, but this operation can be repeated

later to add more drives to an array.



Figure 9-14 Adding a new drive to array



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