A linux utility used to manage software RAID devices.

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13
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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 ...
3
votes
1answer
414 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:...
3
votes
1answer
6k views

recovery data from RAID and disk failure (Linux)

Some background A friend of mine was using in his office a NAS Buffalo-LS-WVL with two disks of 1TB each. It seems that the two disks were mounted as raid 1, but, as you will read, probably they have ...
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 ...
12
votes
3answers
5k views

bit rot detection and correction with mdadm

I'm about to re-organise all my HDDs in my linux box nas and would like to use mdadm raid for data protection and its flexibility for reshaping the arrays. However, before I use mdadm for this I'd ...
19
votes
3answers
13k views

Difference between UUID from blkid and mdadm?

Can someone explain the difference between the UUID's reported by blkid and mdadm? On one of our CentOS systems, for example: [root@server ~]# blkid | grep /dev/md1 /dev/md1: UUID="32cb0a6e-8148-44e9-...
11
votes
1answer
22k views

New md array is auto-read-only and has resync=PENDING

I've created a new md array with the following command: mdadm --create /dev/md1 -l 1 -n 2 /dev/sd[ed]1 But now /proc/mdstat shows the array as "auto-read-only" with resync=PENDING: ~ # cat /proc/...
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 ...
2
votes
1answer
402 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 ...
1
vote
2answers
1k views

Raid devices are mounted with different UUID

Centos 7.1 64. This is what I have: Two raids, but not md0 and md1 [root@localhost]# cat /proc/mdstat Personalities : [raid1] md126 : active raid1 sdb2[1] sda2[0] 974711616 blocks super 1.0 [2/...
5
votes
1answer
159 views

Why does mdadm believe my raid1 “has failed so using --add cannot work”?

TLDR: Trying to add a blank partition to a degraded RAID1 with mdadm 3.3.2 (Debian Jessie) fails, saying the (perfectly working!) array has "failed" and "--add cannot work". Is it telling me of a real ...
4
votes
1answer
3k views

Grub fails to install - Debian Wheezy with mdadm RAID1 and GPT partition table

I've been trying all day to get my new Wheezy install completed but it fail to install Grub every time. I'm using x64 netinstall iso. Here is my partition table: Model: ATA ST3000DM001-1CH1 (scsi) ...
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-...
4
votes
0answers
6k views

Linux md RAID: /dev/md0 vs. /dev/md/0

On newer systems /usr/share/mdadm/mkconf (the script that is used to generate /etc/mdadm/mdadm.conf) tends to use the device name /dev/md/0 instead of /dev/md0: new-system ~ # /usr/share/mdadm/mkconf ...
3
votes
0answers
62 views

What chunks are mismatched in a Linux md array?

This is a repost of a question I asked on ServerFault and was automatically deleted for lack of activity. Let's hope it will have better luck here. After performing a "check" (by writing check to /...
3
votes
2answers
3k views

New RAID array will not auto assemble, leads to boot problems

I had just asked this question where I was unable to boot after installing a new RAID1 Array. I was able to get to the terminal, but once I sorted that out I realized that my problem isn't so much an ...
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 ...
3
votes
2answers
308 views

raid5 exchange 1 of 3 harddrives [duplicate]

I want to exchange a Harddrive which is in a pre-failing state, (some reallocated sectors) which is used in a raid5 array with 3 disks (software raid with mdadm). Is it possible to set a new ...
2
votes
1answer
379 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 ...
2
votes
1answer
2k views

convert /dev/md0 to /dev/sda1

I used a Software-RAID I and want to access the data without RAID now. After mdadm --fail /dev/md0 /dev/sda1 mdadm --remove /dev/md0 /dev/sda1 I tried mount -t ext4 /dev/sda1 /mnt but dmesg ...
1
vote
2answers
528 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 ...