[CentOS] CentOS 7 install on one RAID 1 [not-so-SOLVED]

Eugene Poole etpoole60 at comcast.net
Thu Jan 26 18:10:46 UTC 2017


First let me say I am not a true expert, but I am experienced.

If this machine you purchased was some name brand, you must be speaking 
about hardware raid, true? If this is true, it normally presents you 
with what looks like a standard drive (/dev/sda) for every 2 drives 
configured as raid-1. Also, most name brand servers give you a bootable 
machine day one.

If you are using software raid, you must have configured it yourself.  
Here is what my custom machine has:

2 - 120 GB SSD

2 - 4 TB spinning drives

During my CentOS 7 install is where I performed the software raid-1 
configuration. I never do the default partition configuration so here is 
my setup (used fdisk -l):

Disk /dev/sda: 120.0 GB, 120034123776 bytes, 234441648 sectors
Units = sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disk label type: dos
Disk identifier: 0x0001d7e8

    Device Boot      Start         End      Blocks   Id  System
/dev/sda1            2048   134604799    67301376   fd  Linux raid 
autodetect
/dev/sda2       134604800   184752127    25073664   fd  Linux raid 
autodetect
/dev/sda3       184752128   233191423    24219648   fd  Linux raid 
autodetect
/dev/sda4       233191424   234440703      624640    5  Extended
/dev/sda5   *   233195520   234440703      622592   fd  Linux raid 
autodetect

Disk /dev/sdb: 120.0 GB, 120034123776 bytes, 234441648 sectors
Units = sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disk label type: dos
Disk identifier: 0x000085a6

    Device Boot      Start         End      Blocks   Id  System
/dev/sdb1            2048   134604799    67301376   fd  Linux raid 
autodetect
/dev/sdb2       134604800   184752127    25073664   fd  Linux raid 
autodetect
/dev/sdb3       184752128   233191423    24219648   fd  Linux raid 
autodetect
/dev/sdb4       233191424   234440703      624640    5  Extended
/dev/sdb5   *   233195520   234440703      622592   fd  Linux raid 
autodetect

Disk /dev/sdc: 4000.8 GB, 4000787030016 bytes, 7814037168 sectors
Units = sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 4096 bytes
I/O size (minimum/optimal): 4096 bytes / 4096 bytes
Disk label type: gpt


#         Start          End    Size  Type            Name
  1         2048   1699579903  810.4G  Linux RAID
  2   1699579904   3399157759  810.4G  Linux RAID
  3   3399157760   3911510015  244.3G  Linux RAID
  4   3911510016   5611087871  810.4G  Linux RAID

Disk /dev/sdd: 4000.8 GB, 4000787030016 bytes, 7814037168 sectors
Units = sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 4096 bytes
I/O size (minimum/optimal): 4096 bytes / 4096 bytes
Disk label type: gpt


#         Start          End    Size  Type            Name
  1         2048   1699579903  810.4G  Linux RAID
  2   1699579904   3399157759  810.4G  Linux RAID
  3   3399157760   3911510015  244.3G  Linux RAID
  4   3911510016   5611087871  810.4G  Linux RAID

My df -h display shows me the following:

/dev/md126      583M   317M   224M   59%   /boot

I have basically the definitions using CentOS 6 and CentOS 7 and it's my 
understanding you must have a /boot device.  Also during installation of 
CentOS 7 when writing the MBR to the MD device (in my case md126) it 
writes the information to both sda and sdb. With CentOS 6, according to 
HowToForge there are extra steps required to get the MBR on both sda and 
sdb.

I have not had to replace either of these SSD, but I have had to replace 
spinning drives on my CentOS 6 machines in the past.

Gene


On 1/26/2017 7:00 AM, centos-request at centos.org wrote:
>
> No. Brand new machine, pulled it out of the box and racked it. NOTHING on the
> internal SSDs. Made an md RAID 0 on the raw disks - /dev/sda /dev/sdb. No
> partitions, nothing. However, when I bring it up, fdisk shows an MBR with no
> partitions. I can, however, mount /dev/md127p3 as /mnt/sysimage, and all is there.
>
> Did I need to make a single partition, on each drive, and then make the RAID 1
> out of *those*? I don't think I need to have /boot not on a RAID.
>
> 	mark
>
>
>
> ------------------------------
>
>

-- 
Eugene Poole
Woodstock, Georgia




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