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[ubuntu] mdadm adding a disk to a root RAID5 issues

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http://ubuntuforums.org – Hi All, I am going to be building a NAS/Mini server box soon using Ubuntu Server. In the meantime I have been practicing the raid setup on virtual-box machines. I am using 20GB drives to test it. The issue is that I have 6x 2TB drives. However, on the initial setup, I will only be able to use 4 Drives and then add the extra 2 drives later. I have decided to go with RAID5. Building the 4 drive setup on the virtual box is no problem. Machine boots up and works without issue. I am setting the raid up during the installation. Giving last 4gb on raid as swap and rest as root. I am g (Hardware)

dayu's picture
Submitted by dayu on 10/14/2012

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So here is what I have currently:

8 SAS Drives total 6 Drives setup as RAID 5 as Virtual 1. 1 Drive setup as Hot Spare. 1 Drive in Ready state that is not part of the RAID and is not set as a hot spare.

Basically, everything on this server is setup on the RAID 5 as one virtual disk (OS, data, etc) and partitioned out. I want to separate things out a bit.

I have setup Raid 1 & Raid 10 in Virtual Box for learning purpose.

The following Partitions for 4 Hard Drives:

I make a 100mb partition (/boot) on four drives and make that a raid 1 partition.

Then with the remaining space on each drive, I've setup software raid 10 and configure it to LVM. In the LVM I setup a 4gb swap partition and 20GB for root partition (/) as ext4.

So I ran into an interesting situation. I setup a raid 5 with 6+1 drives. ~9.5tb total. each drive is 2TB. File system is on a seperate 500gb drive over sata 1 as well as the hot-swap.

I have 6 1tb drives in a RAID5. 1 drive went down. On the RAID was 2 virtual machines that I really need back up and running. The spare drive I have to put in the server is a 1.5tb drive, which exceeds the physical per drive limit of the 2020SA. The drive is found in the disk utility, but it is not found in the array management section. I cannot add the drive to the array to have it rebuild.

I need to decide myself between RAID5 and RAID6.

The servers have a hardware-RAID controller and 6 drives each.

The drives are RE3 enterprise western digital 1TB drives. The data sheet says MTTF = 1.2Mio hours, Bit error rate = 1/10^15

On another Server there are even 6 Seagate SAS Drives (172GB each) with MTTF = 1.6Mio hours, Bit error rate = 1/10^16.

I had a major server failure. The OS is fine and back up and running. Before I plug my raid drives back in and try and mount it I need to ask this simple question.

The drives that originally mapped /dev/sda(b/c) are unknown to me. I have no idea of knowing which drive in the raid was /dev/sda to the OS. If I connect them in the wrong order will mdadm figure this out or will I break the raid?

I have a Virtual Host server build with Ubuntu and Xen

SO

Ubuntu 12.04.1 LTS 64Bits xen-hypervisor-4.1

Disk

Hitachi SAS 15K 147GB (x2) in a Volume group sda1 1GB /boot sda2 146GB lvm sdb1 147GB lvm

Every virtual machine has minimum two LV (root, swap)

I have available three new disks Hitachi SAS 15K 600GB i want create a RAID5 with this disk and migrate all partitions from the VG.

I have an old Athlon XP 3000 machine that I keep around as a file server.

It's currently got three 1TB drives which I had setup as mdadm raid 5 on FC10. The machine's original drive held the superblock for the raid array and it just had a massive heart attack.

I previously had a raid5 with mdadm using four 2TB drives.