Hi,

Is it possible to create a Hot spare in raid levels. I need to create a hot spare for a meta device, if any disks in that fails, automatically hot spare disk come into position of failed disk.

Yes assuming you're talking about software RAID.

Type "man mdadm" and have a look at the "-x" option.

Hi,

I stop a meta device using mdadm -S /dev/md1

after that I tried to start again using

mdadm -As /dev/md1

mdadm: /dev/md1 not identified in config file.

so what is the config file, and how we can make entries in that file.

can be:
/etc/mdadm/mdadm.conf
/etc/mdadm.conf

You list devices used, raid level, stuff you would tell it when starting an array with mdadm.
mine:
DEVICES /dev/sdb1 /dev/sdc1 /dev/sdd1 /dev/sde1 /dev/sdf1
ARRAY /dev/md0 devices=/dev/sd[bcdef]1 level=raid5 num-devices=5 metadata=0.90 UUID=665cd099:7ae19af3:87cb1de4:fe062f1b

Simple raid5 config file.

Hot spares are allowed.

If I remember, you can add a spare drive by adding a drive to an array but only telling it to use less than it has (/dev/sda /dev/sdb /dev/sdb 2 drives)

man mdadm
man mdadm.conf
google mdadm spares