Q:

What is the recommended partition scheme for my Ubuntu Server?

I am going to deploy Ubuntu server having following servers on it:

Bind server
DHCP server
LAMP Server
OpenSSH Server
Ldap server
Mongodb database
FTP server
Mail server
Samba server
NFS server
In the future,  I want to set up Openstack for PAAS. 

I currently have a Raid 5 filesystem with 10TB storage.
How should I set up my partition scheme?
I am looking to ensure that I don't have problems in future and that storage size can be easily expanded. Can you suggest a partition scheme giving specific percentage of storage to partitions like /, /boot, /var, /etc?

A:

Before you decide on partitioning schemes it might help to actually understand the reasons for splitting various parts of the linux.
Firstly multiple partitions are 'safer' since if one filesystem is damaged, the others should be alright. This won't save you from a disk failure. Backups would, as might the parity scheme in your raid level.
Secondly it was a way to use multiple drives of different styles before LVM - this is moot for you 
Source - Linux Installation and getting started
In short, the multi partition scheme is sort of a relic of older times, continued for legacy reasons. If you need to ask why, you're better off with a single partition.
In the modern context the smart partitioning method would be to use a single large partition (and a second one, optionally for swap, swap files would be an option). Use LVM so you can add disks if you can if you think you may need to add space. A single large partition means things will handle themselves as long as there's enough space, and you can backup /etc/ /user/local and /home, and use that and a list of installed packages should a bare metal recovery be needed.

A:

I generally recommend a /boot of 1GB, a / of 20GB, and a /data which uses the rest of the available space.  This is so that you can get through a fsck / in a hurry if need be; nothing sucks more than having to sit through three hours or more of fsck just to see if your system will be willing to boot at all!
Aside from that, be sure to use LVM on top of your RAID5; it's hard to give further advice without knowing more details of your RAID array - is it hardware, or is it kernel RAID (mdraid)?  Etc.
One other note - you might consider RAID10 instead of RAID5, depending on how serious your space needs are.  RAID10 will give you less available storage for the same number and size of drives (n/2 instead of n-1), but it will be both higher performance and more resilient in the event of device failure than RAID5.  (It will also be much, much, MUCH higher performance when actually running in degraded mode if and when a device DOES fail.)

