Using symbolic links with a secondary filesystem, e.g. SSDs and SAN storage

By Shyam_Moolayilkalarikkal posted Jun 30, 2014 02:24 PM


SSDs and SAN storage can provide many benefits over the traditional HDD. SSDs provide a much better read/write performance at the cost of being more expensive per GB. SAN storage can provide flexibility of storing data in one place at the cost of performance. For both set-ups, we prefer that AMP is installed on one filesystem to avoid complexity. If this is not feasible, we can use symbolic links to "map" the most commonly used files over to the secondary SSD or SAN storage. This will allow the AMP to function as normal while it offloads the majority of most accessed files to the secondary filesystem.

Stop AMP services and disable Postgres before modifying files:
# amp_disable
# service postgresql stop

Move two commonly accessed directories to the SAN filesystem. The SAN filesystem location is the place you have the SAN storage mounted such as /san:
# mv /var/airwave [SSD or SAN STORAGE LOCATION i.e. /san]/var_airwave
# mv /var/lib/pgsql [SSD or SAN STORAGE LOCATION i.e. /san]/var_lib_pgsql

Symbolically link the folders from the new location to their original location:
# ln -s [SSD or SAN STORAGE LOCATION i.e. /san]/var_airwave /var/airwave
# ln -s [SSD or SAN STORAGE LOCATION i.e. /san]/var_lib_pgsql /var/lib/pgsql

Re-enable the AMP:
# service postgresql start
# amp_enable

You can verify that your setup is accurate by viewing the created symbolic links. They should look like the following:
# ls -ld /var/airwave
lrwxrwxrwx 1 root root 14 Feb 3 15:56 /var/airwave -> /ssid/airwave/
# ls -ld /var/lib/pgsql
lrwxrwxrwx 1 root root 12 Feb 3 15:56 /var/lib/pgsql -> /ssid/pgsql/