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...!!!!!!!!!!!!!

Configure Virtual Serial Port

1)      /etc/securetty  -append
ttyS0
ttyS1

2)      /etc/inittab  - uncomment and modify
S0:12345:respawn:/sbin/agetty -L 115200 ttyS0 vt100

3)      /boot/grub/menu.lst – modify the line of running kernel
root (hd0,0)
    kernel /vmlinuz-2.6.16.60-0.69.1-smp root=/dev/vg00/lvol1 vga=normal nomodeset 3 resume=/dev/vg00/lvol2 splash=silent showopts
crashkernel=256M@16M console=ttyS0,115200
    initrd /initrd-2.6.16.60-0.69.1-smp

Kdump memory requirement

---------------------------------------------------------------------------
    Configuring crashkernel on RHEL6.0 and RHEL6.1 kernels
---------------------------------------------------------------------------

Some mappings of ram and appropriate crashkernel values:

ram size        crashkernel parameter        ram / crashkernel factor
>0GB            128MB                        15
>2GB            256MB                        23
>6GB            512MB                        15
>8GB            768MB                        31

Linux Swapiness

The swappiness parameter controls the tendency of the kernel to move processes out of physical memory and onto the swap disk. Because disks are much slower than RAM, this can lead to slower response times for system and applications if processes are too aggressively moved out of memory.

swappiness can have a value of between 0 and 100

swappiness=0 tells the kernel to avoid swapping processes out of physical memory for as long as possible
swappiness=100 tells the kernel to aggressively swap processes out of physical memory and move them to swap cache


The default setting in Linux is swappiness=60. Reducing the default value of swappiness will probably improve overall performance for a typical desktop installation. A value of swappiness=10 is recommended, but feel free to experiment.

To check the swappiness value use command: cat /proc/sys/vm/swappiness

To make a change permanent, edit the configuration file with your favorite editor:

vi /etc/sysctl.conf
and add following parameter to the end of the file like so:
vm.swappiness=10
Save the file and reboot.

System-wide File Descriptors (FD) Limits

Many application such as Oracle database or Apache web server needs this range quite higher. So you can increase the maximum number of open files by setting a new value in kernel variable /proc/sys/fs/file-max as follows (login as the root):
# sysctl -w fs.file-max=100000

Above command forces the limit to 100000 files. You need to edit /etc/sysctl.conf file and put following line so that after reboot the setting will remain as it is:
# vi /etc/sysctl.conf

Append a config directive as follows:
fs.file-max = 100000

Save and close the file. Users need to log out and log back in again to changes take effect or just type the following command:
# sysctl -p

Verify your settings with command:
# cat /proc/sys/fs/file-max

OR
# sysctl fs.file-max

1) Add the following line to /etc/security/limits.conf

webuser hard nofile 64000
then login as webuser

su - webuser
2) Edit following two files for webuser

append .bashrc and .bash_profile file by running

echo "ulimit -n 64000" >> .bashrc ; echo "ulimit -n 64000" >> .bash_profile
3) Log out, then log back in and verify that the changes have been made correctly:

$ ulimit -a | grep open
open files                      (-n) 64000