Say, I have configured Hardware RAID. Is there any way I can know that through login to linux box?

HW RAID will just look like an ordinary drive device, only very large, while soft raid will have special volume labels and use mdadmin. So just look for them.

The point of HW RAID is that the controller does all the raid stuff and presents the entire usit to the OS as a single drive which the OS accesses like any other drive.

You may be thinking of fake raid - the kind you get built in to some mobos.
These will use a special driver specific to the board, so look for it and dmraid. You can also discover the mobo name and look it up online

I dint understand your point..
So You mean We can know about Software RAID not the Hardware RAID. Correct?

Pretty much - though if /dev/hdf turns out to be 1024 terabytes it is kind of a hint.
Similarly, if you know that it is RAID, but you want to know which kind, the absence of software raid would also be a clue.

What are you trying to do?

Just in search of command which can give clue so that I neednot to go to Bios.

Hye,

to get information about the physical disks in your hardware RAID, the vendor of the controller should provide you with some kind of management tool. For example Dell and HP provides such software as an Add-on for Linux. Check what hardware RAID you are using and check on vendors homepage if such a tool is available there.

Yes, but, what do you need one for?
If you installed it, then you already know.
If you are troubleshooting someone elses, then you should look at the bios anyway.
I ask because it sounds like you are trying to do something which has another method.

You have to try some sleuthing to discover the nature of installed raid (or install the vendors raid management tools ... but you need to knew it is raid before you can do that.)

dmraid(8) is useful for discovering software raid too.

dmraid -r

lists all discovered raid devices with formats and levels. HW raid won't count. If a fake raid was not set up via dmraid, then it may not show either - it may use some other software.

soft raid usually has device files with names like md0 and md1 - so

ls /dev/md*

should discover them.
Fakeraid arrays do not have systematic names. If you are lucky the volumes will have "ARRAY" in their names.

fdisk -l

will also provide clues - usually it fails to find a partition table on raid drives.

lsmod

should list any special drivers for fake raid.

Basically, for fake raid, you should go into bios: it is so much easier.