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Old 11-26-2017, 11:27 PM   #1
etpoole60
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Attempting Software RAID-1 On CentOS 6 And 2 - 4 TB Hard Drives


I've a machine I'm attempting to replace that has a total of 6 hard drives (4 - 1TB and 2 - 2TB). So I thought I would save port space by just getting 2 - 4TB drives and a 120GB SSD for the OS and swap.

I found out that fdisk won't deal with drives as large as that and whatever is used during installation also won't deal with drives that large.

So post install I tried to use gdisk and I was able to create partitions but mdadm doesn't 'see' the gdisk partitions. Does anyone have a idea what I am doing wrong?

I've seen some articles about using parted. Is there a tutorial on doing software raid using gdisk or parted with large hard drives?

If I were wealthy I would just go buy 4 - 2TB drives and put the 4's on the shelf.

Hasn't someone realized that drives aren't getting smaller???

TIA
Gene
 
Old 11-27-2017, 12:05 AM   #2
syg00
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Quote:
Originally Posted by etpoole60 View Post
Hasn't someone realized that drives aren't getting smaller???
Everybody realised it years ago - guess who's missing the boat here ?. Get current and there is no problem. In fact the current LVM handles RAID (including RAID1) better than mdadm IMHO.
I haven't looked at CentOS 7 for quite a while, but it would be the sensible resolution.
 
Old 11-27-2017, 03:22 PM   #3
etpoole60
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I know the required mdadm and lvm commands, that's not the problem.

The problem is Linux - it can't seem to handle large hard drives from bare metal. I don't use machines that have Windows on them so all of the disk drives are empty.

The installation should be smart enough to recognize that the disk drives are to large for fdisk and then use something else. I also think that the layout of the hard drives should look the same (i.e. gdisk doesn't produce a Extended partition) and a code showing what program partitioned the disks. What do you use with a 10TB hard drive??? Do the people who build hard disk confer with M$ so they can update their code?

TIA
Gene
 
Old 11-27-2017, 04:14 PM   #4
jefro
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Some folks might suggest that mbr plus motherboard issues could be a problem past 2TB.
An up to date OS plus motherboard support plus GPT over MBR should fix issue.
 
Old 11-27-2017, 08:31 PM   #5
syg00
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Quote:
Originally Posted by etpoole60 View Post
The problem is Linux - it can't seem to handle large hard drives from bare metal.
Rubbish.

As I said above, use current versions of the tools. Even fdisk does gpt these days, and has been able to for a while.
 
Old 11-27-2017, 11:21 PM   #6
etpoole60
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I live in the Metro-Atlanta area and we have 2 - Fry's and 2 - MicroCenter stores. I go to a specific store where I found that members of the Support area are aware of Linux and what hardware generally will work (hence the nVidia video cards on my machines). That's where I learned that hybrid (part spinning and part solid state) hard drives are not suggested for RAID-1.

I don't play games, RIP music, or generally surf the net on my Linux machines. On a single machine I have the gnome GUI so that I can keep my fingers into Oracle Database DBA knowledge.

So any motherboard that will run Windows 7 64 will run CentOS 6 64 doing what I need.

TIA
Gene
 
Old 11-28-2017, 12:17 AM   #7
AwesomeMachine
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Centos 6 is old.

On another note, you don't need to put the system drive in the raid array. It would be silly to do so, because it would just go in the pool.

I'm not trying to be mean. Just think about it for a sec.
 
Old 12-01-2017, 01:14 AM   #8
tofino_surfer
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Quote:
I found out that fdisk won't deal with drives as large as that and whatever is used during installation also won't deal with drives that large.
If you are using MBR partitioning the size limit is 2.2TB (2TiB). If the fdisk you are using does not support GPT then you can't use it.

Quote:
So post install I tried to use gdisk and I was able to create partitions but mdadm doesn't 'see' the gdisk partitions. Does anyone have a idea what I am doing wrong?
If you don't post the commands you used or gdisk listings of the drives how would we know. Did you set the partition type code to FD00 for Linux raid autodetect on each partition ? You need to do this in gdisk for each partition before using mdadm or mdadm might not see them which is the problem you are having.

Code:
$ sudo gdisk -l /dev/sdd
GPT fdisk (gdisk) version 0.8.6

Partition table scan:
  MBR: protective
  GPT: present

Found valid GPT with protective MBR; using GPT.
Disk /dev/sdd: 5860533168 sectors, 2.7 TiB

Number  Start (sector)    End (sector)  Size       Code  Name
   1            2048      5860532223   2.7 TiB     FD00 

$ cat /proc/mdstat
Personalities : [raid1] 
md0 : active raid1 sdd1[0] sde1[1]
      2930263928 blocks super 1.2 [2/2] [UU]
Quote:
I've seen some articles about using parted. Is there a tutorial on doing software raid using gdisk or parted with large hard drives?
As long as you are using GPT size shouldn't matter. Last year I created an mdadm RAID1 from 2 WD 3TB HDD and put lvm on top. I had no problems.

Quote:
The problem is Linux - it can't seem to handle large hard drives from bare metal. I don't use machines that have Windows on them so all of the disk drives are empty.
My two 3TB drives were empty. No problems.

Last edited by tofino_surfer; 12-01-2017 at 01:19 AM.
 
  


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