There are 25 systems in our shop, all linux based, a linux based server,
and synology Disk Station running raid 1.   The Disk Station has 12 TB
of space.  6 TB per for each raid level.

We buy only one brand of disk with the black label.  They are typically
1 TB.

User boxes has a SSD drive for the OS and a 2 TB disk for the users
space and 32 G RAM. and a quad or six core AMD processor.  The graphics
boxes get a Video card with lots of ram.  3 D rendering on a slow video
care wast's a lot of users time.

The server has a SSD for the OS and 6 TB for user apps /
library /usr/local and /opt.  It also has a mirror disk that keeps a
copy of the server locally.

These systems are on 24 / 7 and accumulate a lot of hours.  No matter
what the make mechanical disks have a life span.  For grins I used to do
a post mortum on disk that failed.   There were to types of failures,
the spring that returns the arm holding the heads cracks.  The second
type of failure is the main bearings.  Newer disk seem to have less of a
bearing failure rate.  
To prevent operational problems we just swap out the disk on each box at
about 5,000 to 7,000 hr.  The manufacturer says they are good for 10,000
hr. See the fine print in the Waranty,  You have to remember this is a
money making operation and down time is costly.

Backups run at 12:29 and 0:29 in the AM.  At the end of the morning back
up a copy is sent to a remote site. 

For security we shut down the network at 6:20 PM, bring it up at 0:01 AM
and shut it down after back up is complete.  We bring it back up at 6:45
AM.  
10 yeas ago we had a fixed IP and the Chineese found it by just
continually pounding on the door.  The return IP was 4 hops to a city
north east of Shanghi.  They had installed a root kit on our server,
disabled cron.  When you changed the passwd to the server a few
millisecond later it was sent to china.  We got rid of the fixed IP and
reloaded all the systems.  So when you shout down the network to your
provider the next time your start it you get a different IP.

We don't give the disks away as they contain a lot of design data,
SW,Cad programs, part programs for our mill etc.  We donate them to a
charity that drills the disks and recycles the rest.

Larry Linder