Configuration Examples

This section presents sample configurations and shows various steps and decisions involved in setting up the mcf file on a server.

Note that all sample configurations could have automated libraries and other removable media devices defined as well, essentially extending the file system beyond the size of the disk cache. Removable media device configurations are shown in only one example. For information about configuring removable media devices, see Chapter 2, Configuring Storage Devices for Archiving, in Sun Storage Archive Manager 5.3 Configuration and Administration Guide.

The sample configurations assume that the file system is loaded on the system and that all file systems are unmounted.

How to Create a Round-Robin Disk Configuration

This sample configuration illustrates a Sun QFS file system that separates the metadata onto a low-latency disk. Round-robin allocation is used on four partitions. Each disk is on a separate controller.

This procedure assumes the following:

The metadata device is a single partition (s6) used on controller 5, logical unit number (LUN) 0 of the device designated as equipment number 11.
The data devices consist of four disks attached to four controllers.

Create the mcf file, as shown in the following code example.

# Sun QFS disk cache configuration
# Round-robin mcf example
# Equipment       Eq   Eq    Fam.  Dev     Additional
# Identifier      Ord  Type  Set   State   Parameters
#-----------      ---   --  ------ ------  ------------------
qfs1                1   ma   qfs1
/dev/dsk/c5t0d0s6  11   mm   qfs1    on
/dev/dsk/c1t1d0s6  12   mr   qfs1    on
/dev/dsk/c2t1d0s6  13   mr   qfs1    on
/dev/dsk/c3t1d0s6  14   mr   qfs1    on
/dev/dsk/c4t1d0s6  15   mr   qfs1    on

Create the /qfs mount point for the /qfs1 file system.
```
# mkdir /qfs
```
Use the sammkfs command to initialize the file system.
The following example uses the default 64-kilobyte DAU.
```
# sammkfs qfs1
```
Modify the /etc/vfstab file.
The Sun QFS file system with mr data devices uses striped allocation as a default, so you must set stripe=0 for round-robin allocation. To explicitly set round-robin on the file system, set stripe=0, as follows:
```
qfs1    -    /qfs    samfs    -    yes    stripe=0
```
Mount the file system.
```
# mount /qfs
```

How to Create a Striped Disk Configuration

In this sample configuration, file data is striped to four data partitions by default.

This procedure assumes the following:

The metadata device is a single partition (s6) used on controller 0, LUN 1. Metadata is written to equipment number 11 only.
The data devices consist of four disks attached to four controllers. Each disk is on a separate controller.

Create the mcf file, as shown in the following code example.

# Sun QFS disk cache configuration
# Striped Disk mcf example
# Equipment       Eq   Eq    Fam.  Dev.    Additional
# Identifier      Ord  Type  Set   State   Parameters
#-----------      ---   --  ------ ------  ------------------
qfs1               10   ma  qfs1
/dev/dsk/c0t1d0s6  11   mm  qfs1     on
/dev/dsk/c1t1d0s6  12   mr  qfs1     on
/dev/dsk/c2t1d0s6  13   mr  qfs1     on
/dev/dsk/c3t1d0s6  14   mr  qfs1     on
/dev/dsk/c4t1d0s6  15   mr  qfs1     on

Create the /qfs mount point for the /qfs1 file system.
```
# mkdir /qfs
```
Use the sammkfs command to initialize the file system.
The default DAU is 64 kilobytes, but the following example sets the DAU size to 128 kilobytes:
```
# sammkfs -a 128 qfs1
```
With this configuration, any file written to this file system is striped across all of the devices in increments of 128 kilobytes.
Modify the /etc/vfstab file.
The Sun QFS file system uses striped allocation by default. This example sets the stripe width as stripe=1, which is the default. The following setting stripes data across all four of the mr devices with a stripe width of 1 DAU:
```
qfs1    -    /qfs    samfs    -    yes    stripe=1
```
Mount the file system.
```
# mount /qfs
```

How to Create a Striped Group Configuration

Striped groups enable you to group RAID devices together for very large files. A DAU is represented by one bit in the bitmap. If the striped group has n devices, n multiplied by the DAU is the minimum allocation. Only one bit in the bitmap is used to represent n x DAU.

The minimum disk space allocated in a striped group is as follows:

minimum-disk-space-allocated = DAU x number-of-disks-in-the-group

Note - Writing a single byte of data fills the entire minimum disk space allocated in a striped group. Striped groups are used for very specific applications. Make sure that you understand the effects of using striped groups with your file system.

Files with lengths less than the aggregate stripe width times the number of devices (in this example, files less than 128 kilobytes x 4 disks = 512 kilobytes in length) still use 512 kilobytes of disk space. Files larger than 512 kilobytes have space allocated for them as needed in total space increments of 512 kilobytes.

The devices within a striped group must be the same size. You cannot add devices to increase the size of a striped group. You can use the samgrowfs command to add additional striped groups, however. For more information, see the samgrowfs(1M) man page.

This sample configuration illustrates a Sun QFS file system that separates the metadata onto a low-latency disk. Two striped groups are set up on four drives.

This procedure assumes the following:

The metadata device is a single partition (s6) used on controller 0, LUN 1.
The data devices consist of four disks (two groups of two identical disks) attached to four controllers. Each disk is on a separate LUN. The entire disk is used for data storage, assuming that partition 6 occupies the entire disk.

Create the mcf file, as shown in the following code example.

# Sun QFS disk cache configuration
# Striped Groups mcf example
# Equipment       Eq   Eq    Fam.  Dev.    Additional
# Identifier      Ord  Type  Set   State   Parameters
#-----------      ---   --  ------ ------  ------------------
qfs1               10   ma  qfs1
/dev/dsk/c0t1d0s6  11   mm  qfs1     on
/dev/dsk/c1t1d0s6  12   g0  qfs1     on
/dev/dsk/c2t1d0s6  13   g0  qfs1     on
/dev/dsk/c3t1d0s6  14   g1  qfs1     on
/dev/dsk/c4t1d0s6  15   g1  qfs1     on

Create the /qfs mount point for the /qfs1 file system.
```
# mkdir /qfs
```
Use the sammkfs command to initialize the file system.
The following example sets the DAU size to 128 kilobytes.
```
# sammkfs -a 128 qfs1
```
Modify the /etc/vfstab file.
The following example uses the default setting of stripe=0, which essentially specifies a round-robin allocation from striped group g0 to striped group g1.
```
 qfs1    -    /qfs    samfs    -    yes   stripe=0
```
This /etc/vfstab file sets the stripe width using the stripe= option. This example has two striped groups, g0 and g1. With the stripe=0 specification, files are written round-robin around the two striped groups.

Note - To change the configuration of the striped group after it is created, you must issue another sammkfs command.
Mount the file system.
```
# mount /qfs
```

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