Managing Disk Volumes

C H A P T E R 3

This chapter describes redundant array of independent disks (RAID) concepts, and how to configure and manage RAID disk volumes using the Sun Netra T5220 server’s on-board serial attached SCSI (SAS) disk controller.

This chapter contains the following sections:

Patch Requirements

Disk Volumes

RAID Technology

Hardware Raid Operations

Patch Requirements

To configure and use RAID disk volumes on the Sun Netra T5220 server, you must install the appropriate patches. For the latest information on patches for the Sun Netra T5220 server, see the latest product notes for your system.

Installation procedures for patches are included in text README files that accompany the patches.

Disk Volumes

From the perspective of the on-board disk controller on the Sun Netra T5220 server, disk volumes are logical disk devices comprising one or more complete physical disks.

Once you create a volume, the operating system uses and maintains the volume as if it were a single disk. By providing this logical volume management layer, the software overcomes the restrictions imposed by physical disk devices.

The onboard disk controller of the Sun Netra T5220 server provides for the creation of as many as two hardware RAID volumes. The controller supports either two-disk RAID 1 (integrated mirror, or IM) volumes, or up to eight-disk RAID 0 (integrated stripe, or IS) volumes.

Note - Due to the volume initialization that occurs on the disk controller when a new volume is created, properties of the volume such as geometry and size are unknown. RAID volumes created using the hardware controller must be configured and labeled using format(1M) prior to use with the Oracle Solaris Operating System. See To Configure and Label a Hardware RAID Volume for Use in the Oracle Solaris Operating System, or the format(1M) man page for further details.

Volume migration (relocating all RAID volume disk members from one Sun Netra T5220 chassis to another) is not supported. If you must perform this operation, contact your service provider.

RAID Technology

RAID technology enables the construction of a logical volume, made up of several physical disks, in order to provide data redundancy, increased performance, or both. The Sun Netra T5220 server’s on-board disk controller supports both RAID 0 and RAID 1 volumes.

This section describes the RAID configurations supported by the on-board disk controller:

Integrated Stripe, or IS volumes (RAID 0)

Integrated Mirror, or IM volumes (RAID 1)

Integrated Stripe Volumes (RAID 0)

Integrated Stripe volumes are configured by initializing the volume across two or more physical disks, and sharing the data written to the volume across each physical disk in turn, or striping the data across the disks.

Integrated Stripe volumes provide for a logical unit (LUN) that is equal in capacity to the sum of all its member disks. For example, a three-disk IS volume configured on 72-gigabyte drives will have a capacity of 216 gigabytes.

FIGURE 3-1 Graphical Representation of Disk Striping

This illustration is a conceptual drawing showing how write speeds can be increased by writing (striping) information to multiple disks.

Caution - There is no data redundancy in an IS volume configuration. Thus, if a single disk fails, the entire volume fails, and all data is lost. If an IS volume is manually deleted, all data on the volume is lost.

IS volumes are likely to provide better performance than IM volumes or single disks. Under certain workloads, particularly some write or mixed read-write workloads, I/O operations complete faster because the I/O operations are being handled in a round-robin fashion, with each sequential block being written to each member disk in turn.

Integrated Mirror Volumes (RAID 1)

Disk mirroring (RAID 1) is a technique that uses data redundancy, two complete copies of all data stored on two separate disks, to protect against loss of data due to disk failure. One logical volume is duplicated on two separate disks.

FIGURE 3-2 Graphical Representation of Disk Mirroring

This illustration is a conceptual drawing showing disk mirroring.

Whenever the operating system needs to write to a mirrored volume, both disks are updated. The disks are maintained at all times with exactly the same information. When the operating system needs to read from the mirrored volume, the OS reads from whichever disk is more readily accessible at the moment. This functionality can result in enhanced performance for read operations.

Caution - Creating RAID volumes using the on-board disk controller destroys all data on the member disks. The disk controller’s volume initialization procedure reserves a portion of each physical disk for metadata and other internal information used by the controller. Once the volume initialization is complete, you can configure the volume and label it using the format(1M) utility. You can then use the volume in the Oracle Solaris OS.

Hardware Raid Operations

On the Sun Netra T5220 server, the SAS controller supports mirroring and striping using the Oracle Solaris OS raidctl utility.

A hardware RAID volume created under the raidctl utility behaves slightly differently than one created using volume management software. Under a software volume, each device has its own entry in the virtual device tree, and read-write operations are performed to both virtual devices. Under hardware RAID volumes, only one device appears in the device tree. Member disk devices are invisible to the operating system, and are accessed only by the SAS controller.

Physical Disk Slot Numbers, Physical Device Names, and Logical Device Names for Non-RAID Disks

To perform a disk hot-plug procedure, you must know the physical or logical device name for the drive that you want to install or remove. If your system encounters a disk error, often you can find messages about failing or failed disks in the system console. This information is also logged in the /var/adm/messages files.

These error messages typically refer to a failed hard drive by its physical device name (such as /devices/pci@1f,700000/scsi@2/sd@1,0) or by its logical device name (such as c0t1d0). In addition, some applications might report a disk slot number (0 through 3).

You can use TABLE 3-1 to associate internal disk slot numbers with the logical and physical device names for each hard drive.

TABLE 3-1 Disk Slot Numbers, Logical Device Names, and Physical Device Names
Disk Slot Number	Logical Device Name ^[1]	Physical Device Name
Slot 0	`c0t0d0`	`/devices/pci@0/pci@0/pci@2/scsi@0/sd@0,0`
Slot 1	`c0t1d0`	`/devices/pci@0/pci@0/pci@2/scsi@0/sd@1,0`
Slot 2	`c0t2d0`	`/devices/pci@0/pci@0/pci@2/scsi@0/sd@2,0`
Slot 3	`c0t3d0`	`/devices/pci@0/pci@0/pci@2/scsi@0/sd@3,0`

To Create a Hardware Mirrored Volume

1. Verify which hard drive corresponds with which logical device name and physical device name, using the raidctl command:

# raidctl
No RAID volumes found.

See Physical Disk Slot Numbers, Physical Device Names, and Logical Device Names for Non-RAID Disks.

The preceding example indicates that no RAID volume exists. In another case:

# raidctl
RAID    Volume  RAID            RAID            Disk
Volume  Type    Status          Disk            Status
------------------------------------------------------------
c0t0d0  IM      OK               c0t0d0           OK
                                   c0t1d0           OK

In this example, a single IM volume has been enabled. It is fully synchronized and is online.

The Sun Netra T5220 server’s on-board SAS controller can configure as many as two RAID volumes. Prior to volume creation, ensure that the member disks are available and that there are not two volumes already created.

The RAID status might be:

OK - Indicating that the RAID volume is online and fully synchronized.

RESYNCING - Indicating that the data between the primary and secondary member disks in an IM are still synchronizing.

DEGRADED - Indicating that a member disk is failed or otherwise offline.

FAILED - Indicating that volume should be deleted and reinitialized. This failure can occur when any member disk in an IS volume is lost, or when both disks are lost in an IM volume.

The Disk Status column displays the status of each physical disk. Each member disk might be OK, indicating that it is online and functioning properly, or it might be FAILED, MISSING, or otherwise OFFLINE, indicating that the disk has hardware or configuration issues that need to be addressed.

For example, an IM with a secondary disk that has been removed from the chassis appears as:

# raidctl
RAID    Volume  RAID            RAID            Disk
Volume  Type    Status          Disk            Status
------------------------------------------------------
c0t0d0  IM      DEGRADED        c0t0d0          OK
                                c0t1d0          MISSING

See the raidctl(1M) man page for additional details regarding volume and disk status.

Note - The logical device names might appear differently on your system, depending on the number and type of add-on disk controllers installed.

2. Type the following command:

# raidctl -c primary secondary

The creation of the RAID volume is interactive, by default. For example:

# raidctl -c c0t0d0 c0t1d0
Creating RAID volume c0t0d0 will destroy all data on member disks, proceed 
(yes/no)? yes
Volume ’c0t0d0’ created
#

As an alternative, you can use the -f option to force the creation if you are sure of the member disks, and sure that the data on both member disks can be lost. For example:

# raidctl -f -c c0t0d0 c0t1d0
Volume ’c0t0d0’ created
#

When you create a RAID mirror, the secondary drive (in this case, c0t1d0) disappears from the Oracle Solaris device tree.

3. To check the status of a RAID mirror, type the following command:

# raidctl
RAID    Volume  RAID          RAID          Disk      
Volume  Type    Status        Disk          Status    
--------------------------------------------------------
c0t0d0  IM      RESYNCING     c0t0d0        OK        
                              c0t1d0        OK

The preceding example indicates that the RAID mirror is still resynchronizing with the backup drive.

The following example shows that the RAID mirror is synchronized and online.

# raidctl
RAID    Volume  RAID            RAID            Disk
Volume  Type    Status          Disk            Status
------------------------------------------------------
c0t0d0  IM      OK              c0t0d0          OK
                                c0t1d0          OK

The disk controller synchronizes IM volumes one at a time. If you create a second IM volume before the first IM volume completes its synchronization, the first volume’s RAID status will indicate RESYNCING, and the second volume’s RAID status will indicate OK. Once the first volume has completed, its RAID status changes to OK, and the second volume automatically starts synchronizing, with a RAID status of RESYNCING.

Under RAID 1 (disk mirroring), all data is duplicated on both drives. If a disk fails, replace it with a working drive and restore the mirror. For instructions, see To Perform a Mirrored Disk Hot-Plug Operation.

For more information about the raidctl utility, see the raidctl(1M) man page.

To Create a Hardware Mirrored Volume of the Default Boot Device

Due to the volume initialization that occurs on the disk controller when a new volume is created, the volume must be configured and labeled using the format(1M) utility prior to use with the Oracle Solaris Operating System (see To Configure and Label a Hardware RAID Volume for Use in the Oracle Solaris Operating System). Because of this limitation, raidctl(1M) blocks the creation of a hardware RAID volume if any of the member disks currently have a file system mounted.

This section describes the procedure required to create a hardware RAID volume containing the default boot device. Since the boot device always has a mounted file system when booted, an alternate boot medium must be employed, and the volume created in that environment. One alternate medium is a network installation image in single-user mode (refer to the Oracle Solaris 10 Installation Guide for information about configuring and using network-based installations).

1. Determine which disk is the default boot device

From the OpenBoot ok prompt, type the printenv command, and if necessary the devalias command, to identify the default boot device. For example:

ok printenv boot-device
boot-device =         disk
 
ok devalias disk
disk                  /pci@0/pci@0/pci@2/scsi@0/disk@0,0

2. Type the boot net -s command

ok boot net -s

3. Once the system has booted, use the raidctl(1M) utility to create a hardware mirrored volume, using the default boot device as the primary disk.

See To Create a Hardware Mirrored Volume. For example:

# raidctl -c -r 1 c0t0d0 c0t1d0
Creating RAID volume c0t0d0 will destroy all data on member disks, proceed 
(yes/no)? yes
Volume  c0t0d0  created
#

4. Install the volume with the Oracle Solaris OS using any supported method.

The hardware RAID volume c0t0d0 appears as a disk to the Oracle Solaris installation program.

Note - The logical device names might appear differently on your system, depending on the number and type of add-on disk controllers installed.

To Create a Hardware Striped Volume

1. Verify which hard drive corresponds with which logical device name and physical device name.

See Disk Slot Numbers, Logical Device Names, and Physical Device Names.

To verify the current RAID configuration, type:

# raidctl
No RAID volumes found.

The preceding example indicates that no RAID volume exists.

Note - The logical device names might appear differently on your system, depending on the number and type of add-on disk controllers installed.

2. Type the following command:

# raidctl -c -r 0 disk1 disk2 ...

The creation of the RAID volume is interactive, by default. For example:

# raidctl -c -r 0 c0t1d0 c0t2d0 c0t3d0
Creating RAID volume c0t1d0 will destroy all data on member disks, proceed 
(yes/no)? yes
Volume ’c0t1d0’ created
#

When you create a RAID striped volume, the other member drives (in this case, c0t2d0 and c0t3d0) disappear from the Oracle Solaris device tree.

As an alternative, you can use the -f option to force the creation if you are sure of the member disks, and sure that the data on all other member disks can be lost. For example:

# raidctl -f -c -r 0 c0t1d0 c0t2d0 c0t3d0
Volume ’c0t1d0’ created
#

3. To check the status of a RAID striped volume, type the following command:

# raidctl
RAID    Volume  RAID            RAID            Disk
Volume  Type    Status          Disk            Status
--------------------------------------------------------
c0t1d0  IS     OK               c0t1d0          OK        
                                c0t2d0          OK        
                                c0t3d0          OK

The example shows that the RAID striped volume is online and functioning.

Under RAID 0 (disk striping), there is no replication of data across drives. The data is written to the RAID volume across all member disks in a round-robin fashion. If any one disk is lost, all data on the volume is lost. For this reason, RAID 0 cannot be used to ensure data integrity or availability, but can be used to increase write performance in some scenarios.

For more information about the raidctl utility, see the raidctl(1M) man page.

To Configure and Label a Hardware RAID Volume for Use in the Oracle Solaris Operating System

After a creating a RAID volume using raidctl, use format(1M) to configure and label the volume before attempting to use it in the Oracle Solaris OS.

1. Start the format utility:

# format

The format utility might generate messages about corruption of the current label on the volume, which you are going to change. You can safely ignore these messages.

2. Select the disk name that represents the RAID volume that you have configured.

In this example, c0t2d0 is the logical name of the volume.

# format
Searching for disks...done
AVAILABLE DISK SELECTIONS:
        0. c0t0d0 <SUN72G cyl 14084 alt 2 hd 24 sec 424>
           /pci@0/pci@0/pci@2/scsi@0/sd@0,0
        1. c0t1d0 <SUN72G cyl 14084 alt 2 hd 24 sec 424>
           /pci@0/pci@0/pci@2/scsi@0/sd@1,0
        2. c0t2d0 <SUN72G cyl 14084 alt 2 hd 24 sec 424>
           /pci@0/pci@0/pci@2/scsi@0/sd@2,0
Specify disk (enter its number): 2
selecting c0t2d0
[disk formatted]
FORMAT MENU:
         disk       - select a disk
         type       - select (define) a disk type
         partition  - select (define) a partition table
         current    - describe the current disk
         format     - format and analyze the disk
         fdisk      - run the fdisk program
         repair     - repair a defective sector
         label      - write label to the disk
         analyze    - surface analysis
         defect     - defect list management
         backup     - search for backup labels
         verify     - read and display labels
         save       - save new disk/partition definitions
         inquiry    - show vendor, product and revision
         volname    - set 8-character volume name
         !<cmd>     - execute <cmd>, then return
         quit

3. Type the type command at the format> prompt, then select 0 (zero) to auto configure the volume.

For example:

format> type
 
AVAILABLE DRIVE TYPES:
         0. Auto configure
         1. DEFAULT
         2. SUN72G
         3. SUN72G
         4. other
Specify disk type (enter its number)[3]: 0
c0t2d0: configured with capacity of 68.23GB
<LSILOGIC-LogicalVolume-3000 cyl 69866 alt 2 hd 16 sec 128>
selecting c0t2d0
[disk formatted]

4. Use the partition command to partition, or slice, the volume according to your desired configuration.

See the format(1M) man page for additional details.

5. Write the new label to the disk using the label command.

format> label
Ready to label disk, continue? yes

6. Verify that the new label has been written by printing the disk list using the disk command.

format> disk
 
AVAILABLE DISK SELECTIONS:
        0. c0t0d0 <SUN72G cyl 14084 alt 2 hd 24 sec 424>
           /pci@0/pci@0/pci@2/scsi@0/sd@0,0
        1. c0t1d0 <SUN72G cyl 14084 alt 2 hd 24 sec 424>
           /pci@0/pci@0/pci@2/scsi@0/sd@1,0
        2. c0t2d0 <LSILOGIC-LogicalVolume-3000 cyl 69866 alt 2 hd 16 sec 128>
           /pci@0/pci@0/pci@2/scsi@0/sd@2,0
Specify disk (enter its number)[2]:

Note that c0t2d0 now has a type indicating it is an LSILOGIC-LogicalVolume.

7. Exit the format utility.

The volume can now be used in the Oracle Solaris OS.

Note - The logical device names might appear differently on your system, depending on the number and type of add-on disk controllers installed.

To Delete a Hardware RAID Volume

1. Verify which hard drive corresponds with which logical device name and physical device name.

See Disk Slot Numbers, Logical Device Names, and Physical Device Names.

2. Determine the name of the RAID volume, type:

# raidctl
RAID    Volume  RAID            RAID            Disk
Volume  Type    Status          Disk            Status
------------------------------------------------------
c0t0d0  IM      OK              c0t0d0          OK
                                c0t1d0          OK

In this example, the RAID volume is c0t1d0.

Note - The logical device names might appear differently on your system, depending on the number and type of add-on disk controllers installed.

3. To delete the volume, type the following command:

# raidctl -d mirrored-volume

For example:

# raidctl -d c0t0d0
RAID Volume ‘c0t0d0’ deleted

In the event that the RAID volume is an IS volume, the deletion of the RAID volume is interactive, for example:

# raidctl -d c0t0d0
Deleting volume c0t0d0 will destroy all data it contains, proceed
(yes/no)? yes
Volume ’c0t0d0’ deleted.
#

The deletion of an IS volume results in the loss of all data that it contains. As an alternative, you can use the -f option to force the deletion if you are sure that you no longer need the IS volume, or the data it contains. For example:

# raidctl -f -d c0t0d0
Volume ’c0t0d0’ deleted.
#

4. To confirm that you have deleted the RAID array, type the following command:

# raidctl

For example:

# raidctl
No RAID volumes found

For more information, see the raidctl(1M) man page.

To Perform a Mirrored Disk Hot-Plug Operation

1. Verify which hard drive corresponds with which logical device name and physical device name.

See Disk Slot Numbers, Logical Device Names, and Physical Device Names.

2. To confirm a failed disk, type the following command:

# raidctl

If the Disk Status is FAILED, then the drive can be removed and a new drive inserted. Upon insertion, the new disk should be OK and the volume should be RESYNCING.

For example:

# raidctl
RAID    Volume  RAID            RAID            Disk
Volume  Type    Status          Disk            Status
--------------------------------------------------------
c0t1d0  IM      DEGRADED        c0t1d0          OK        
                                c0t2d0          FAILED

This example indicates that the disk mirror has degraded due to a failure in disk c0t2d0.

Note - The logical device names might appear differently on your system, depending on the number and type of add-on disk controllers installed.

3. Remove the hard drive, as described in your Sun Netra T5220 Server Service Manual.

There is no need to issue a software command to bring the drive offline when the drive has failed.

4. Install a new hard drive, as described in your Sun Netra T5220 Server Service Manual.

The RAID utility automatically restores the data to the disk.

5. To check the status of a RAID rebuild, type the following command:

# raidctl

For example:

# raidctl
RAID    Volume  RAID            RAID            Disk
Volume  Type    Status          Disk            Status
--------------------------------------------------------
c0t1d0  IM      RESYNCING       c0t1d0          OK        
                                c0t2d0          OK

This example indicates that RAID volume c0t1d0 is resynchronizing.

If you issue the command again once synchronization has completed, it indicates that the RAID mirror is finished resynchronizing and is back online:

# raidctl
RAID    Volume  RAID            RAID            Disk
Volume  Type    Status          Disk            Status
--------------------------------------------------------
c0t1d0  IM      OK              c0t1d0          OK        
                                c0t2d0          OK

For more information, see the raidctl(1M) man page.

To Perform a Nonmirrored Disk Hot-Plug Operation

1. Verify which hard drive corresponds with which logical device name and physical device name.

See Disk Slot Numbers, Logical Device Names, and Physical Device Names.

Ensure that no applications or processes are accessing the hard drive.

2. Type the following command:

# cfgadm -al

For example:

# cfgadm -al
Ap_Id           Type         Receptacle   Occupant      Condition
c0              scsi-bus     connected    configured    unknown
c0::dsk/c0t0d0  disk         connected    configured    unknown
c0::dsk/c0t1d0  disk         connected    configured    unknown
c0::dsk/c0t2d0  disk         connected    configured    unknown
c0::dsk/c0t3d0  disk         connected    configured    unknown
c1              scsi-bus     connected    configured    unknown
c1::dsk/c1t0d0  CD-ROM       connected    configured    unknown
usb0/1          unknown      empty        unconfigured  ok
usb0/2          unknown      empty        unconfigured  ok
usb1/1.1        unknown      empty        unconfigured  ok
usb1/1.2        unknown      empty        unconfigured  ok
usb1/1.3        unknown      empty        unconfigured  ok
usb1/1.4        unknown      empty        unconfigured  ok
usb1/2          unknown      empty        unconfigured  ok
#

Note - The logical device names might appear differently on your system, depending on the number and type of add-on disk controllers installed.

The -al options return the status of all SCSI devices, including buses and USB devices. In this example, no USB devices are connected to the system.

Note - While you can use the Oracle Solaris OS cfgadm install_device and cfgadm remove_device commands to perform a hard drive hot-plug procedure, these commands issue the following warning message when you invoke them on a bus containing the system disk:

# cfgadm -x remove_device c0::dsk/c0t1d0
Removing SCSI device: /devices/pci@1f,4000/scsi@3/sd@1,0
This operation will suspend activity on SCSI bus: c0
Continue (yes/no)? y
dev = /devices/pci@780/pci@0/pci@9/scsi@0/sd@1,0
cfgadm: Hardware specific failure: failed to suspend: 
     Resource              Information       
------------------  -------------------------
/dev/dsk/c0t0d0s0   mounted filesystem "/"   
/dev/dsk/c0t0d0s6   mounted filesystem "/usr"

This warning is issued because these commands attempt to quiesce the (SAS) SCSI bus, but the server firmware prevents it. This warning message can be safely ignored in the Sun Netra T5220 server, but the following step avoids this warning message altogether.

3. Remove the hard drive from the device tree.

To remove the hard drive from the device tree, type the following command:

# cfgadm -c unconfigure Ap-Id

For example:

# cfgadm -c unconfigure c0::dsk/c0t3d0

This example removes c0t3d0 from the device tree. The blue OK-to-Remove LED lights.

4. Verify that the device has been removed from the device tree.

Type the following command:

# cfgadm -al
Ap_Id           Type         Receptacle   Occupant      Condition
c0              scsi-bus     connected    configured    unknown
c0::dsk/c0t0d0  disk         connected    configured    unknown
c0::dsk/c0t1d0  disk         connected    configured    unknown
c0::dsk/c0t2d0  disk         connected    configured    unknown
c0::dsk/c0t3d0  unavailable  connected    configured    unknown
c1              scsi-bus     connected    unconfigured  unknown
c1::dsk/c1t0d0  CD-ROM       connected    configured    unknown
usb0/1          unknown      empty        unconfigured  ok
usb0/2          unknown      empty        unconfigured  ok
usb1/1.1        unknown      empty        unconfigured  ok
usb1/1.2        unknown      empty        unconfigured  ok
usb1/1.3        unknown      empty        unconfigured  ok
usb1/1.4        unknown      empty        unconfigured  ok
usb1/2          unknown      empty        unconfigured  ok
#

Note that c0t3d0 is now unavailable and unconfigured. The corresponding hard drive OK-to-Remove LED is lit.

5. Remove the hard drive, as described in Sun Netra T5220 Server Service Manual.

The blue OK-to-Remove LED goes out when you remove the hard drive.

6. Install a new hard drive, as described in Sun Netra T5220 Server Service Manual.

7. Configure the new hard drive.

Type the following command:

# cfgadm -c configure Ap-Id

For example:

# cfgadm -c configure c1::dsk/c0t3d0

The green Activity LED flashes as the new disk at c1t3d0 is added to the device tree.

8. Verify that the new hard drive is in the device tree.

Type the following command:

# cfgadm -al
Ap_Id           Type         Receptacle   Occupant      Condition
c0              scsi-bus     connected    configured    unknown
c0::dsk/c0t0d0  disk         connected    configured    unknown
c0::dsk/c0t1d0  disk         connected    configured    unknown
c0::dsk/c0t2d0  disk         connected    configured    unknown
c0::dsk/c0t3d0  disk         connected    configured    unknown
c1              scsi-bus     connected    configured    unknown
c1::dsk/c1t0d0  CD-ROM       connected    configured    unknown
usb0/1          unknown      empty        unconfigured  ok
usb0/2          unknown      empty        unconfigured  ok
usb1/1.1        unknown      empty        unconfigured  ok
usb1/1.2        unknown      empty        unconfigured  ok
usb1/1.3        unknown      empty        unconfigured  ok
usb1/1.4        unknown      empty        unconfigured  ok
usb1/2          unknown      empty        unconfigured  ok
#

Note - c0t3d0 is now listed as configured.

^{1 (TableFootnote) The logical device names might appear differently on your system, depending on the number and type of add-on disk controllers installed.}