What is a Mirror Log ?

LVM maintains a small log which it uses to keep track of which regions are in sync with the mirror or mirrors. 

By default, this log is kept on disk, which keeps it persistent across reboots and ensures that the mirror does not need to be re-synced every time a machine reboots or crashes. 

You can specify instead that this log be kept in memory with the --mirrorlog core argument; this eliminates the need for an extra log device, but it requires that the entire mirror be resynchronized at every reboot.

Linux LVM Mirroring (RAID -1 ) Part II

Now going to mirror the logical volume:

[root@test ~]# lvconvert -m1 /dev/oracle/oracle_lv
  oracle/oracle_lv: Converted: 0.0%
  oracle/oracle_lv: Converted: 100.0%
[root@test ~]#

[root@test ~]# lvdisplay -m /dev/oracle/oracle_lv
  --- Logical volume ---
  LV Name                /dev/oracle/oracle_lv
  VG Name                oracle
  LV UUID                O9W6go-l2AC-0XP9-GvLw-tL2C-bjeI-YoWmDG
  LV Write Access        read/write
  LV Status              available
  # open                 1
  LV Size                1.00 GiB
  Current LE             256
  Mirrored volumes       2
  Segments               1
  Allocation             inherit
  Read ahead sectors     auto
  - currently set to     256
  Block device           253:0

  --- Segments ---
  Logical extent 0 to 255:
    Type                mirror
    Mirrors             2
    Mirror size         256
    Mirror log volume   oracle_lv_mlog
    Mirror region size  512.00 KiB
    Mirror original:
      Logical volume    oracle_lv_mimage_0
      Logical extents   0 to 255
    Mirror destinations:
      Logical volume    oracle_lv_mimage_1
      Logical extents   0 to 255


[root@test ~]#

[root@test ~]# pvs -o +lv_name

  PV         VG     Fmt  Attr PSize PFree LV

  /dev/sdb   oracle lvm2 a--  5.00g 4.00g [oracle_lv_mimage_1]

  /dev/sdb   oracle lvm2 a--  5.00g 4.00g

  /dev/sdc   oracle lvm2 a--  5.00g 3.99g [oracle_lv_mimage_0]

  /dev/sdc   oracle lvm2 a--  5.00g 3.99g [oracle_lv_mlog]

  /dev/sdc   oracle lvm2 a--  5.00g 3.99g

[root@test ~]#

Linux LVM Mirroring (RAID -1 ) Part I

This post I am going to show how to mirror a logical volume:

[root@test ~]# df -TH /oracle
Filesystem    Type     Size   Used  Avail Use% Mounted on
/dev/mapper/oracle-oracle_lv
              ext4     1.1G   1.1G      0 100% /oracle
[root@test ~]#

Before mirroring:

[root@test ~]# lvdisplay -m /dev/oracle/oracle_lv

  --- Logical volume ---

  LV Name                /dev/oracle/oracle_lv

  VG Name                oracle

  LV UUID                O9W6go-l2AC-0XP9-GvLw-tL2C-bjeI-YoWmDG

  LV Write Access        read/write

  LV Status              available

  # open                 1

  LV Size                1.00 GiB

  Current LE             256

  Segments               1

  Allocation             inherit

  Read ahead sectors     auto

  - currently set to     256

  Block device           253:0

  --- Segments ---

  Logical extent 0 to 255:

    Type                linear

    Physical volume     /dev/sdc

    Physical extents    0 to 255

Initializing and adding a new disk to the VG Oracle:

[root@test ~]# pvcreate /dev/sdb

  Writing physical volume data to disk "/dev/sdb"

  Physical volume "/dev/sdb" successfully created

[root@test ~]# vgextend /dev/oracle /dev/sdb

  Volume group "oracle" successfully extended

[root@test ~]# 

RMAN-03009: failure of backup command on ORA_DISK_1 channel at 07/09/2014 11:21:25 ORA-19602: cannot backup or copy active file in NOARCHIVELOG mode

The reason for the above error is the due to the database is configured to run in NOARCHIVE Mode.

So to fix the error, We need to convert the database to ARCHIVE Mode.

SQL> archive log list;
Database log mode              No Archive Mode
Automatic archival             Disabled
Archive destination            /u01/app/oracle/product/11.2.0/db_1/dbs/arch
Oldest online log sequence     2
Current log sequence           4
SQL>

Converting  to ARCHIVE Mode.

SQL> alter database archivelog;

alter database archivelog

*

ERROR at line 1:

ORA-01126: database must be mounted in this instance and not open in any instance

SQL>

So, doing that before the database should be in Mounted state.

Database closed.

Database dismounted.

ORACLE instance shut down.

SQL> startup mount;

ORACLE instance started.

Total System Global Area  392495104 bytes

Fixed Size                  2213696 bytes

Variable Size             138414272 bytes

Database Buffers          247463936 bytes

Redo Buffers                4403200 bytes

Database mounted.

SQL> alter database archivelog;

Database altered.

SQL> archive log list;

Database log mode              Archive Mode

Automatic archival             Enabled

Archive destination            /u01/app/oracle/product/11.2.0/db_1/dbs/arch

Oldest online log sequence     2

Next log sequence to archive   4

Current log sequence           4

SQL> alter database open;

Database altered.

SQL> 

Bingo...!!!!!!!!!!!!!