disksetup

Describes the disksetup command that formats disks for use by MapR storage.

Description

The disksetup command formats specified disks for use by MapR storage, and adds those disks to the disktab file.

You do not need to set up Redundant Array of Independent Disks (RAID) on disks used by the MapR Filesystem. MapR uses disksetup to set up storage pools. In most cases, you should let MapR calculate storage pools using the default stripe width of two or three disks. If you anticipate a high volume of random-access I/O, you can use the -W option to specify larger storage pools of up to 8 disks each.

See Setting Up Disks for MapR for more information about when and how to use disksetup.

Syntax

/opt/mapr/server/disksetup
    [-F]
    [-G]
    [-X]
    [-M]
    [-W <stripe_width>]
    <disk list file>

Options

Option

Description

-F

Forces formatting of all specified disks. Disks that are already formatted for MapR are not reformatted by disksetup unless you specify this option. The -F option fails when a filesystem has an entry in the disktab file, is mounted, or is in use. Call maprcli disk remove to remove a disk entry from the disktab file.

-G

Generates the disktab file contents from input disk list, but does not format disks. Use this option if the disktab file is completely lost, and you need to regenerate it based on an input list of disks assigned to MapR-FS. This option reads the GUID from the provided disks, and generates the disktab output to stdout. You can redirect the output to a file.

-X Fixes disktab contents from /proc/partitions, but does not format disks. Use this option if there is a change in the names of the disk devices referenced by disktab, but the disks themselves are still usable. For example, if /dev/sdb has been renamed to /dev/sdf but the device itself has the same GUID, only the disktab contents need to be updated to point to /dev/sdf.

-M

Uses the maximum available number of disks per storage pool.

-W

Specifies the number of disks per storage pool.

Examples

Setting up disks specified in the file /tmp/disks.txt:
/opt/mapr/server/disksetup -F /tmp/disks.txt
Reformatting all disks

To reformat all disks, remove the disktab file and issue the disksetup -F command to format the disk:

/opt/mapr/server/disksetup -F

To reformat a particular disk from the disktab, use the maprcli disk remove and maprcli disk add commands. For more information, see Setting Up Disks for MapR.

Specifying disks

To specify the disks to be formatted for use by the MapR cluster, create a text file /tmp/disks.txt listing the disks and partitions for use by MapR on the node. Each line lists either a single disk, or all applicable partitions on a single disk. When listing multiple partitions on a line, separate each partition by spaces. For example:

/dev/sdb
/dev/sdc1 /dev/sdc2 /dev/sdc4
/dev/sdd

Later, when you run disksetup to format the disks, specify the disks.txt file. For example:

/opt/mapr/server/disksetup -F /tmp/disks.txt
Important:

The disksetup command removes all data from the specified disks. Ensure that you specify the disks correctly, and that you have backed up any data that you wish to keep.

If you are re-using a node that was used previously in another cluster, be sure to format the disks to remove any traces of data from the old cluster.

Warning: Run disksetup only after you run the configure.sh .
Test Purposes Only: Using a Flat File for Storage

When setting up a small cluster for evaluation purposes, if a particular node does not have physical disks or partitions available to dedicate to the cluster, you can use a flat file on an existing disk partition as the node's storage. Create at least a 16GB file, and include a path to the file in the disk list file for the disksetup script.

The following example creates a 20 GB flat file (bs=1G specifies 1 gigabyte blocks, multiplied by count=20) at /root/storagefile:

dd if=/dev/zero of=/root/storagefile bs=1G count=20

Next, add the following entry to the disk list file /tmp/disks.txt to be used by disksetup:

/root/storagefile