Insight on partitioning a LAMP Server design issue

[tmetro-blu-5a1Jt6qxUNc at public.gmane.org (Tom Metro)]

Stephen Goldman wrote:
>     The device is a brand new Dell server with: 
>     /dev/sda    raid one 160 G
>     /dev/sdb    raid five 270G 
...
>     There is a total of six drives :
>         Raid one for the OS
>         Raid five for the data & db

So really you're talking about /dev/md0 .. /dev/md4 for the first set 
(given your proposed list of partitions), and /dev/md5 for the second. 
As Jerry suggested, using LVM would let you have just /dev/md0 and 
/dev/md1, with LVM used to split up /dev/md0 into the collection of 
partitions you desire. See:

http://www.tldp.org/HOWTO/Software-RAID-HOWTO-11.html


>     32 G phyiscal ram
>     /            20  G swap

Traditionally swap gets set to a multiplier of RAM, but with 32 GB of 
RAM, I don't know if this wisdom still holds up. I'd recommend doing 
some research.


>     My plan was to partition [the RAID 1 set] as follows:
> 
>     /            25  G
>     / var       25 G
>     /tmp      20  G
>     /home   remainer

I've set up systems with similar capacities (though with /var and /home 
included with root), and inevitably ended up moving all or most of /var 
to a second disk (or array), along with /home, and having to spend time 
managing space on root. It doesn't take long for a modern system to fill 
up a 25 GB root.

Your primary objective here should be just to keep what is needed to 
boot the system on the RAID 1 set, with a secondary objective of keeping 
/tmp and other variable partitions from crowding out root.

You can accomplish that by sticking with your 20 GB partition for /tmp, 
putting /var and /home on the RAID 5 set, and letting root take up the 
rest of the RAID 1 set.


> I know the Apache can be redirected .. 
> Please confirm that Mysql can be configured to live on the [other RAID set]

Yes, trivial. Either via symlink, mount point, or by modifying the 
setting in /etc/mysql/my.cnf.


> Is there performance gains running the services on the partitiion /dev/sdb

If you have two applications that make heavy use of the disk, it's 
common to distribute them among separate disks. If MySQL, for example, 
is going to see a lot of activity, while having more modest capacity 
requirements compared to Apache, you could put its data files on the 
RAID 1 set. Given that you'll have two storage systems with likely 
different read and write performance, the ideal approach would be to 
benchmark your usage to see what works best.

  -Tom

-- 
Tom Metro
Venture Logic, Newton, MA, USA
"Enterprise solutions through open source."
Professional Profile: http://tmetro.venturelogic.com/