Determine physical disk size

Kristijan · 01-20-2005, 10:34 PM

Hi,

Is there any easy way to determine how many physical disks are attached to a Linux server and the size of each disk.

I have tried using sfdisk, fdisk, df and lspci to try and work this out but to no avail.

We have just noticed that there are two physical drives connected to this box from this command. Is there anyway of finding out the entire size of each drive.

This is the output from grep -i disk /var/log/*

dmesg:Attached scsi disk sda at scsi1, channel 0, id 0, lun 0
dmesg:Attached scsi disk sdb at scsi1, channel 0, id 1, lun 0

Cheers,
-Kristijan

Dark_Helmet · 01-20-2005, 11:01 PM

How about this:

Code:

fdisk -l | grep "^Disk" | cut -f 1 -d ',' | cut -f 3- -d '/'

Kristijan · 01-23-2005, 04:00 PM

Dark_Helmet,

Running that command on my box at home seems to work fine. Shows the exact disk size. I gave it a shot when I got into work this morning and this was the output.

Code:

[root@GEO1 root]# fdisk -l | grep "^Disk" | cut -f 1 -d ',' | cut -f 3- -d '/'
sda: 255 heads
sdb: 255 heads

This is the output of fdisk -l

Code:

[root@GEO1 root]# fdisk -l

Disk /dev/sda: 255 heads, 63 sectors, 4467 cylinders
Units = cylinders of 16065 * 512 bytes

   Device Boot    Start       End    Blocks   Id  System
/dev/sda1   *         1        13    104391   fd  Linux raid autodetect
/dev/sda2            14       140   1020127+  fd  Linux raid autodetect
/dev/sda3           141      4467  34756627+  fd  Linux raid autodetect

Disk /dev/sdb: 255 heads, 63 sectors, 4467 cylinders
Units = cylinders of 16065 * 512 bytes

   Device Boot    Start       End    Blocks   Id  System
/dev/sdb1   *         1        13    104391   fd  Linux raid autodetect
/dev/sdb2            14       140   1020127+  fd  Linux raid autodetect
/dev/sdb3           141      4467  34756627+  fd  Linux raid autodetect

This is the output from df -h

Code:

[root@GEO1 root]# df -h
Filesystem            Size  Used Avail Use% Mounted on
/dev/md0               33G  720M   30G   3% /
/dev/md2               99M   15M   78M  16% /boot
none                 1008M     0 1008M   0% /dev/shm

Can someone clarify the output of df. Does Size show the total size of the disk, or does it just show the total of all the partitions.

For example, if I have a 80GB disk, and make 2 partitions, 30GB and a 20GB partition. Will df show the total size of the 2 partitions (50GB) or will it show the total disk size, including the empty space (80GB)

There is nothing there that exactly tells me /dev/sda = xxGB, or it is there and I can't see it =/

Cheers,
-Kristijan

Dark_Helmet · 01-23-2005, 04:18 PM

The command I gave was just highlighting a specifc portion ofthe fisk output (as you probably guessed).

You can calculate the size of the disk using its geometry listed. You might be able to incorporate this into a shell script to avoid whipping out the calculator, but it's reasonably quick.

Basically, it's just a lot of multiplication: heads * sectors per track * cylinders * bytes per sector = raw size of disk in bytes

In your case, both sda and sdb are identical since they're both in an array (and their numbers match). So, using my calculator:
(heads) * (sectors) * (cylinders) * (bytes) = 255 * 63 * 4467 * 512 = 36742325760

Or, in more familiar terms:
36742325760 / 1000000000 = 36.7 GB
36742325760 / (1024 * 1024 * 1024) = 34.2 GiB

Kristijan · 01-23-2005, 05:56 PM

Dark_Helmet,

Thanks for all the help. If I get some free time, I will throw together a small shell script to automate these calculations. I'll keep you posted if I do

Cheers,
-Kristijan