FDISK LINUX

I have seen a article

. Linux allows only 4 primary partitions. You can have a much larger number of logical partitions by sub-dividing one of the primary partitions. Only one of the primary partitions can be sub-divided.

Does this refer to old IDE disks ? How about the configuration of SCSI hdd, say I have 6 SCSI disks. How do I configure these disks ?

Tks
AXISHKAsked:
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Zephyr ICTCloud ArchitectCommented:
The 4 primary partition limit has to do with the traditional MBR limit, so it doesn't have anything to do with the type of disk, as long as you are using MBR partition layout you are restricted to 4 primary partitions... If you want to avoid that you can switch to GPT, but your hardware needs to support that.

If I had a server with 6 SCSI disks I'd put them either in a RAID config (RAID5 for example) or divide them up, configure the first disk as / (root) make a separate partition on another disk for /opt or something ... Or even make a combination of 2 disks in RAID1 and the others in RAID0 ... Much possibilities.

To configure RAID you need the mdadm tool, there's a nice howto here

Maybe if you can tell us a bit more about  your hardware we can give more specific info if needed.
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rindiCommented:
As mentioned above, MBR is what limits a disk to the 4 primary partitions. It has absolutely nothing to do with the OS (Linux), or the disk architecture (IDE, SCSI, SAS etc).

If you set the disks to GPT, you can have many more than 4 primary partitions, and extended partitions with logical ones inside are no longer supported. Also this has nothing to do with whether the hardware supports it. It is only the OS that needs to support GPT disks. Linux has supported GPT disks for quite some time. One advantage of using GPT disks is that you can use the full capacity of disks larger than 2TB. MBR disks only support capacities of up to 2TB.

With Linux you can also boot from GPT disks using any PC (it doesn't require an UEFI BIOS like Windows does).
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AXISHKAuthor Commented:
I have the RAID already created on the server with.

2 x SCSI disk 600GB (RAID-1)
4 x SCSI disk 600GB (RAID-5)

Can you guide me how to configure the OS then ? Some kinds of step by step guideline would be appreciated..

Tks again.
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rindiCommented:
What are you going to use the server for and what distro? Most distro's don't require a lot of space for the OS. Installation is normally pretty automated and you can just select the defaults unless you have a reason not to. Since it seems you are using real hardware RAID, you don't need mdadm. Your OS will just have to be able to recognize the RAID controller. Modern distro's usually support most controllers out-of-the-box.

Personally I wouldn't recommend using RAID 5 these days. It used to be OK in the old days when disks were of low capacity and very expensive. With today's large disks and their low prices, you can afford a more easy to manage and redundant array, like RAID 6 or 10, or RAID 1 for every array. RAID 5 can easily fail, and it is also easy to make mistakes when rebuilding it or during management which can further cause total failure.
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AXISHKAuthor Commented:
I was told performance for RAID6 is slower than RAID5 though it give better redundancy... correct ?


So, create a one 'big' disk with RAID 6.

Then, simply partition this big disk (sda) with different partition - sda1 (boot), sda2 (swap), sda3 (/root), ... correct ?

Tks
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rindiCommented:
It always depends on your needs, but yes, that is about correct.
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AXISHKAuthor Commented:
Tks
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