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18
votes
2answers
47k views

How to recover a crashed Linux md RAID5 array?

Some time ago I had a RAID5 system at home. One of the 4 disks failed but after removing and putting it back it seemed to be OK so I started a resync. When it finished I realized, to my horror, that 3 ...
20
votes
2answers
14k views

RAIDing with LVM vs MDRAID - pros and cons?

In his answer to the question "mixed raid types", HBruijn suggests using LVM to implement RAID vs the more standard MDRAID. After a little investigation, it seems LVM also supports RAID ...
13
votes
3answers
8k views

How to safely replace a not-yet-failed disk in a Linux RAID5 array?

I have a software RAID5 array (Linux md) on 4 disks. I would like to replace one of the disks with a new one, without putting the array in a degraded state, and if possible, online. How would that ...
17
votes
5answers
12k views

Linux - Repairing bad blocks on a RAID1 array with GPT

The tl;dr: how would I go about fixing a bad block on 1 disk in a RAID1 array? But please read this whole thing for what I've tried already and possible errors in my methods. I've tried to be as ...
3
votes
1answer
397 views

Unable to check a mdadm RAID1 array, says the file system's read only?

I recently migrated a RAID1 from a CentOS 5 system to a CentOS 6 system and ever since when I attempt to perform a check I get the following: $ echo 'check' > /sys/block/md127/md/sync_action -bash:...
6
votes
2answers
2k views

Will the system make sure that mdadm is sync-ed before completing a reboot?

This is a follow up to my crazy mdadm problem. I'm trying to figure out what might have caused sda to get out of sync in the first place. The only thing I can think of is that I had just run a bunch ...
11
votes
2answers
12k views

Is Grub installed to all the MBR of a RAID array by default by the Debian Installer?

If I use the Debian Stable (Squeeze) Installer to install Debian, booting from a RAID1 pair of drives, does it write grub to the MBR of both drives - if not, how should I best protect against a drive ...
10
votes
5answers
55k views

lvm devices under /dev/mapper missing

I'm using Debian squeeze, and running LVM on top of software RAID 1. I just accidentally just discovered that most of the links under /dev/mapper are missing, though my system seems to be still ...
7
votes
2answers
7k views

How to raid-mirror existing root partition?

I'd like to mirror my existing root (and only) partition on an SSD to another disk. It should be a sort of RAID-1, just asymmetric*. I know there's the option mdadm --write-behind, which should do it. ...
7
votes
4answers
7k views

Monitor disk health using smartd (in smartmontools) on a high availability software RAID 1 server

I have a server with three identical SATA/600 3TB drives: /dev/sda, /dev/sdb, /dev/sdc. The drives are partitioned, using GPT with three partitions each: 1 MB: Reserved partition for boot loader 1 ...
8
votes
1answer
17k views

mdadm raid1 and what chunksize (or blocksize) on 4k drives?

I want to use two 3 TB drives in a mdadm raid1 setup (using Debian Sequeeze). The drives use 4k hardware sectors instead of the traditional 512 byte ones. I am a bit confused because on the one hand ...
5
votes
2answers
12k views

Does Grub2 support putting /boot on a RAID5 partition?

It looks like currently most OS installers insist on putting /boot on a non-RAID partition (or the kind of RAID1 partition that "looks like" a non-RAID partition), even the installers that support ...
3
votes
2answers
460 views

raid 1/LVM at the level of directories (aka mknodding a directory)

I just experienced data loss, so I am interested in some form of data duplication. I was thinking of mdadm and companions to raid 1 through software. However, I just want a given, not too big ...
2
votes
1answer
401 views

Drive was unable to assemble into the array

I ran mdadm -A /dev/md0 /dev/sda1 /dev/sdb1 Only /dev/sdb1 was loaded into the array though. I have a few more arrays on the same two drives too. Each time the partition on sda failed. dmesg told ...
4
votes
1answer
63 views

Prevent debian from hindering boot if a software-raid problem exists

I have a computer that I rarely have physical access to. All my access to that computer is done using SSH. On that computer, there's a software RAID5 using MDADM. This array contains data in one ...
4
votes
2answers
9k views

What does mdadm's “spare” number mean?

I created a mdadm-based RAID 5 from six hard drives using the following command: # mdadm --create /dev/md0 --level=5 --raid-devices=5 \ /dev/sdb1 /dev/sdc1 /dev/sdd1 /dev/sde1 /dev/sdf1 \ --spare-...
3
votes
2answers
202 views

Recovering mismatched sectors in a RAID array

I recently got an automated email saying "WARNING: mismatch_cnt is not 0 on /dev/md3". I'm running a software RAID5 array using mdadm on CentOS 6.6 When Googling the message I found this:- The ...
3
votes
1answer
2k views

Software RAID 10 + LVM on mixed drives, sector alignment?

I have 4 2.5" 7.2k drives lying about and I'd like to build some RAID arrays for a bit of VM storage on my KVM lab box. There are 2x 320GB drives and 2x 500GB drives. I'm looking to create a RAID 10 ...
2
votes
1answer
366 views

mixed raid types

I am about to reinitialise my (SW) raid array. Previously the array was raid5 with 4 disks. I've removed one disk in order to install a new additional (larger) drive. What I'd ideally like to do is ...
1
vote
2answers
515 views

Missing mdadm raid5 array reassembles as raid0 after powerout

I had RAID5 array of three disks with no spares. There was a power out, and on reboot, the array failed to come back up. In fact, it the /dev/md127 device disappeared entirely, and was replaced by an ...
1
vote
0answers
60 views

How has this arrangement of RAID disks occurred and is it recoverable?

I some months ago set up two RAID arrays for a system under CentOS 7. I was somewhat confused that the device list included two entries for each array, i.e. one had /dev/md126 and /dev/md126p1. The ...
1
vote
2answers
383 views

Copying linux install from non-RAID/x86 to RAID/x86-64

I'm copying an Ubuntu Server install from an x86 machine with a single hard disk to a new machine with x64 and two identical disks. Two partitions will span the new disks: One small-ish RAID1 for ...