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.. _raid:
######
RAID-1
######
A Redundant Array of Independent Disks (RAID) uses two or more hard disk drives
to improve disk speed, store more data, and/or provide fault tolerance.
There are several storage schemes possible in a RAID array, each offering a
different combination of storage, reliability, and/or performance.
The VyOS system supports a “RAID 1” deployment. RAID 1 allows two or more
disks to mirror one another to provide system fault tolerance. In a RAID 1
solution, every sector of one disk is duplicated onto every sector of all
disks in the array. Provided even one disk in the RAID 1 set is operational,
the system continues to run, even through disk replacement (provided that the
hardware supports in-service replacement of drives).
RAID 1 can be implemented using special hardware or it can be implemented in
software. The VyOS system supports software RAID 1 on two disks.
The VyOS implementation of RAID 1 allows the following:
* Detection and reporting of disk failure
* The ability to maintain system operation with one failed disk
* The ability to boot the system with one failed disk
* The ability to replace a failed disk and initiate re-mirroring
* The ability to monitor the status of remirroring
.. _raid_instalation:
Installation Implications
=========================
The VyOS systems installation utility provides several options for installing
to a RAID 1 set. You can:
* Use the install system to create the RAID 1 set
* Use the underlying Linux commands to create a RAID 1 set before running the
install system command.
* Use a previously-created RAID 1 set.
.. note:: Before a permanent installation, VyOS runs a live installation
Configuration
=============
Single disk, install as normal
------------------------------
When the VyOS system is installed, it automatically detects the presence of two
disks not currently part of a RAID array. In these cases, the VyOS
installation utility automatically offers you the option of configuring RAID 1
mirroring for the drives, with the following prompt.
.. code-block:: none
Would you like to configure RAID 1 mirroring on them?
* If you do not want to configure RAID 1 mirroring, enter “No” at the prompt
and continue with installation in the normal way.
Empty 2+ Disk
-------------
If VyOS system detect two identical disks that are not currently part of a
RAID-1 set, the VyOS installation utility automatically offers you the option
of configuring RAID 1 mirroring for the drives, with the following prompt.
.. code-block:: none
Would you like to configure RAID 1 mirroring on them?
1 - To create a new RAID 1 array, enter “Yes” at the prompt. If the system
detects a filesystem on the partitions being used for RAID 1 it will prompt you
to indicate whether you want to continue creating the RAID 1 array.
.. code-block:: none
Continue creating array?
2 - To overwrite the old filesystem, enter “Yes”.
3 - The system informs you that all data on both drives will be erased. You are
prompted to confirm that you want to continue
.. code-block:: none
Are you sure you want to do this?
4 - Enter “Yes” at the prompt to retain the current VyOS configuration once
installation is complete. Enter “No” to delete the current VyOS
configuration.
.. code-block:: none
Would you like me to save the data on it before I delete it?
5 - Enter “Yes” at the prompt to retain the current VyOS configuration once
installation is complete. Enter “No” to delete the current VyOS configuration.
6 - Continue with installation in the normal way.
Present RAID-1
--------------
When the VyOS software on a system with a RAID 1 set already configured,
the installation utility will detect the array and will display the following
prompt:
.. code-block:: none
Would you like to use this one?
1 - To break apart the current RAID 1 set, enter “No” at the prompt. The
installation utility detects that there are two identical disks and offers you
the option of configuring RAID 1 mirroring on them, displaying the following
prompt:
.. code-block:: none
Would you like to configure RAID 1 mirroring on them?
2 - To decline to set up a new RAID 1 configuration on the disks, enter “No”
at the prompt. The system prompts you to indicate which partition you would
like the system installed on.
.. code-block:: none
Which partition should I install the root on? [sda1]:
3 - Enter the partition where you would like the system installed. The system
then prompts you to indicate whether you want to save the old configuration
data. This represents the current VyOS configuration.
.. code-block:: none
Would you like me to save the data on it before I delete it?
4 - Enter “Yes” at the prompt to retain the current VyOS configuration once
installation is complete. Enter “No” to delete the current VyOS configuration.
5 - Continue with installation in the normal way.
Detecting and Replacing a Failed RAID 1 Disk
--------------------------------------------
The VyOS system automatically detects a disk failure within a RAID 1 set and
reports it to the system console. You can verify the failure by issuing the
show raid command.
To replace a bad disk within a RAID 1 set, perform the following steps:
1 - Remove the failed disk from the RAID 1 set by issuing the following
command:
.. opcmd:: delete raid RAID‐1‐device member disk‐partition
where RAID-1-device is the name of the RAID 1 device (for example, md0) and
disk-partition is the name of the failed disk partition (for example, sdb2).
2- Physically remove the failed disk from the system. If the drives are not
hot-swappable, then you must shut down the system before removing the disk.
3 - Replace the failed drive with a drive of the same size or larger.
4 - Format the new disk for RAID 1 by issuing the following command:
.. opcmd:: format <disk‐device1> like <disk‐device2>
where disk-device1 is the replacement disk (for example, sdb) and
disk-device2 is the existing healthy disk (for example, sda).
5-Add the replacement disk to the RAID 1 set by issuing the following command:
.. opcmd:: add raid <RAID‐1‐device> member <disk‐partition>
where RAID-1-device is the name of the RAID 1 device (for example, md0) and
disk-partition is the name of the replacement disk partition
(for example, sdb2).
Operation
=========
This part introduces how to add a disk partition to a RAID-1 set initiates
mirror synchronization, check and display information.
.. opcmd:: add raid <RAID‐1‐device> member <disk‐partition>
Use this command to add a member disk partition to the RAID 1 set. Adding a
disk partition to a RAID 1 set initiates mirror synchronization, where all
data on the existing member partition is copied to the new partition.
.. opcmd:: format <disk‐device1> like <disk‐device2>
This command is typically used to prepare a disk to be added to a preexisting
RAID 1 set (of which disk-device2 is already a member).
.. opcmd:: show raid <RAID‐1‐device>
shows output for show raid md0 as sdb1 is being added to the RAID 1
set and is in the process of being resynchronized.
.. code-block:: none
vyos@vyos:~$ show raid md0
/dev/md0:
Version : 00.90
Creation Time : Wed Oct 29 09:19:09 2008
Raid Level : raid1
Array Size : 1044800 (1020.48 MiB 1069.88 MB)
Used Dev Size : 1044800 (1020.48 MiB 1069.88 MB)
Raid Devices : 2
Total Devices : 2
Preferred Minor : 0
Persistence : Superblock is persistent
Update Time : Wed Oct 29 19:34:23 2008
State : active, degraded, recovering
Active Devices : 1
Working Devices : 2
Failed Devices : 0
Spare Devices : 1
Rebuild Status : 17% complete
UUID : 981abd77:9f8c8dd8:fdbf4de4:3436c70f
Events : 0.103
Number Major Minor RaidDevice State
0 8 1 0 active sync /dev/sda1
2 8 17 1 spare rebuilding /dev/sdb1
.. opcmd:: show raid <RAID‐1‐device>
Use this command to display the formatting of a hard disk.
.. code-block:: none
vyos@vyos:~$ show disk sda format
Disk /dev/sda: 1073 MB, 1073741824 bytes
85 heads, 9 sectors/track, 2741 cylinders
Units = cylinders of 765 * 512 = 391680 bytes
Disk identifier: 0x000b7179
Device Boot Start End Blocks Id System
/dev/sda1 6 2737 1044922+ fd Linux raid autodetect
|
