linux box HDD size question

[Matt Roth]

>
>
>Hi.. May I know how to check a size of the HDD (s) in a linux box. If I issued the following
>command, does it mean the total HDD size is 30G ??  Could it be some of the HDD space is not used
>??  If yes, how to check the real disk space??  Besides, how do we check what is the RAID type and
>how many HDD is beside the box via linux command or other mean ?
>
>[root at linux root]# df -h
>Filesystem            Size  Used Avail Use% Mounted on
>/dev/sda3             4.0G  289M  3.5G   8% /
>/dev/sda9             6.6G  1.9G  4.5G  30% /apps
>/dev/sda1             250M   45M  193M  19% /boot
>/dev/sda6             5.0G  1.7G  3.1G  36% /home
>none                  1.3G     0  1.3G   0% /dev/shm
>/dev/sda8             2.0G   83M  1.8G   5% /tmp
>/dev/sda7             4.0G  3.1G  712M  82% /usr
>/dev/sda5             6.9G  157M  6.4G   3% /var
>

We have Fedora Core 3 installed on our Dell PowerEdge servers.  Each 
PowerEdge has an onboard PERC RAID controller, which configures the 
drives as the desired RAID type.  To keep things simple, I will refer to 
our two disk setups which are configured as RAID 1s (mirrored).

In these setups, the PERC card effectively hides the fact that there are 
multiple drives from the operating system.  It presents the OS with a 
view of a single disk and handles all of the activities needed to 
maintain the mirror independently.

This presented a problem to us when we were trying to monitor 
RAID-related events (disk failure, mirror rebuild progress, etc).  I 
could find *nothing* through the OS that provided this information, 
because it viewed the entire RAID as a single disk.

We eventually solved the problem by finding software that interfaces 
directly with the RAID controller.  MegaMgr allows us to enter the 
PERC's firmware from the command prompt (previously, this was only 
accessible during the boot process) and provides information about the 
individual drives in the array (size, manufacturer, etc) as well as the 
RAID configuration itself.  MegaMon is a daemon that provides monitoring 
of RAID events from the OS.  The only problem that I've seen so far is 
that MegaMon has a small memory leak, so we cron off a restart of it 
nightly.

This is all specific to a hardware RAID, but I'm assuming that is what 
you have.  I *believe* that if it was a software RAID, all of the 
information that you are seeking would be readily available through the 
OS (see "man mdadm" and the "/proc" pseudo-filesystem).  I don't have 
any experience with software RAIDS, so if anyone reading this disagrees 
please correct me.

The software involved is also specific to our hardware platform (Dell 
PowerEdges with PERC RAID controllers).  It is my hope that the 
information I'm providing gets you looking in the right direction.  Try 
contacting your RAID controller's manufacturer for equivalent software 
if Google doesn't turn anything up.

I hope this was helpful,

Matthew Roth
InterMedia Marketing Solutions
Software Engineer and Systems Developer