A linux utility used to manage software RAID devices.

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How to restore RAID5 Array

I have a RAID5 array consisting of 3 identical 2TB drives. Suddenly GRUB wouldn't boot anymore and gave the error out of disk. Eventually booted a livecd and ran some mdadm commands: mdadm --examine ...
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166 views

Raid 5 rebuild with wrong stripe size & no failed disks - is data lost?

I'm curious if there are hidden complexities to RAID5 and RAID5 rebuilds. My understanding is that (in a 3 disk array) a rebuild would just directly compute the parity of disks 1 & 2 and write ...
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144 views

Revert btrfs to ext4 on mdadm raid

I have a Raid 5 setup using devices rather than partitions. I recently converted the ext4 fs on the md device to btrfs. I was initially happy with btrfs, but to be short, it's eating up CPU cycles ...
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97 views

mount mdadm disk without partition table

I've a debian installation and during the installation I had made 3 mdadm raid disk: swap, root and home. I had done it with partman and it had made the mdadm disk without partition table. Now I want ...
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243 views

Removing failed disk from raid 1

my server (Debian Wheezy) has a failed disk. I have sda and sdb and according to the support of my hoster, sdb needs a replacement. I send them this information with the mdstat: ...
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27 views

RAID boot drive not found after mdadm upgrade

I was having trouble getting a new RAID array to assemble on startup, and before anyone responded to that post, I tried updating mdadm, but this ended up taking a very long time because of all the ...
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1k views

“Spare” disk in a 2-disk mdadm RAID1 array?

I recently had a RAID1 volume fail. It had three primary partitions in it, all participating in separate, but similarly configured VGs. This configuration comes from the fact that the machine is ...
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67 views

File transfer between SSD and RAID array uber-slow

It's really simple: this server has an SSD for the main drive, and a RAID array (mdadm) for storage. Intermittently, it has a problem writing to the array: the write speeds slow down to the point ...
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74 views

Recovering a (not yet created) RAID5 with URE (Unrecoverable read errors)

I wan't to create a RAID5 array at home, the OS is Linux (Kernel 3.15.7) and the array will be created with mdadm. I wan't to create the array with eigth or ten 1TB discs. Let's assume a single drive ...
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530 views

Disable RAID auto detect at runtime

In Linux, I'm partitioning two disks for RAID1 with fdisk. The first disk partitioning succedes, but the second fail because the raid starts automatically and occupy also the second disk (why? it ...
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406 views

Software raid checksumming slow

On my new 24 disk array I get 900 MB/s of raw read or write using dd to all the disks. When I set the disks up as a 24 disk RAID6 I get 400 MB/s write and 600 MB/s read. It seems to be due to ...
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mdadm RAID10 - change broken disk

Tonight my server stopped answering to ssh, ping, so I drove to the server room. Server did not respond to keyboard (even Ctrl-Alt-Del), there was no data on screen (it was black, no symbols on it), ...
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18 views

Boot GRUB2 with Degraded RAID5

I am building a custom NAS with Debian Jessie. Has three 4TB hard drives in a software RAID5 configuration. Works perfectly when all three drives are present. I am trying to test what happens when if ...
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17 views

mdadm arrays referencing the same devices

I've a software RAID setup for one of my servers. Now there are two arrays that reference the same devices (md126/md127 - see below) where one of them is marked inactive. I want to understand what ...
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115 views

Degraded RAID1 array boots with one drive, not with the other

UPDATE It seems initramfs fails to properly mount the array. If I stop and reassemble them, they works: mdadm --stop /dev/md124 mdadm --assemble --run /dev/md124 /dev/sda6 Maybe initrd tries to ...
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91 views

MDADM Array Detection Slowing Down Boot - Why?

I have an AMD64 Gentoo (running systemd) build with a RAID0 root and some other arrays (RAID1 boot, RAID1 home etc..). The boot process is being slowed down quite dramatically as mdadm searches the ...
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24 views

Is it reliable to assemble md from two machines at the same time

Say we have the same disks accessible from two machines. I want to do assembling md from two machines. Is it possible/reliable ? The disks are connected through SAS. All I need to have is reliable ...
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634 views

Help with lost software RAID5 on CentOS 6.5

I've been searching for hours and giving up / too scared to delete all my data. I have a file server running CentOS 6.5 which has 4 WD RED 2TB drives (all > 1 year old) in software raid 5 with mdadm, ...
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211 views

How do you migrate from dmraid to mdadm on a working 14.04?

I installed 14.04 LTS the other day on two Samsung 840 Pro's in RAID0 on my Intel FakeRAID BIOS setup (NO efi). It is running great, however during the initial boot the system seemed to have a broken ...
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29 views

Linux software raid assembled “itself” with failed drive. Why?

I have two raid1 arrays: md3 (sda3 + sdb3) and md5 (sda5 + sdb5). I deliberately failed the sdb disks because I wanted to change the partition table: # mdadm /dev/md3 --fail /dev/sdb3 # mdadm ...
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214 views

RAID5 Arrary disappeard with no HW or SW changes made

I have a R-Pi running XBMC (Linux CaribNAS 3.10.24 #2 PREEMPT Mon Dec 23 05:18:12 UTC 2013 armv6l GNU/Linux) with a 3 disk raid 5 array that has been working up till yesterday when is stopped running ...
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191 views

How to blacklist bad blocks from a MD-raid + dm-crypt + ext4?

I have a ext4 partition, on top of a dm-crypt, on top of a MD-RAID 10. One partition (/dev/sdc1) dropped out of the array with a ton of read errors. I ran the manufacturer provided diagnostic tool ...
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185 views

Grub multi-disk/RAID configuration not booting

I have a system with 2 SSDs configured in BIOS as a Raid 0 volume. The system came with Windows 8 pre-installed. I would like to multi-boot Windows 8 and Debian 7. The Debian installation disk ...
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40 views

Mdadm not adding all disks to raid

A couple of years ago, I installed a raid 5 with mdadm on a fedora box. The old hardware died recently, and I have put the boot disk in a newer desktop pc, and added the thee raid disks via usb. So ...
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696 views

How to make Intel fake RAID 0 volume appear on boot with Ubuntu 14.04 in a multi-boot environment?

I have a computer with a Gigabyte GA-Z97N-Gaming 5 mainboard, a 256 GB drive for booting and two 3 TB drives meant to use in a RAID 0 setup with both ext4 and NTFS partitions. We are planning running ...
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441 views

What are the steps needed to get Redhat/Centos 7 to boot from an mdadm RAID?

I've spent a day on this. Figured it was time to ask. In the end I couldn't get around "Bad magic number in super-block ..." On an average install, my sda exits setup as an EFI. I'm cool with that ...
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530 views

Understanding iostat with Linux software RAID

I'm trying to understand what I see in iostat, specifically the differences between the output for md and sd devices. I have a couple of quite large Centos Linux servers, each with E3-1230 CPU, 16 GB ...
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431 views

mdadm raid 5 missing partitions after reboot

I had a working raid 5 array that had a whole debian install on it (I set it up during a debian install). I'd been using it a couple of days, all was fine, but since I created it during debian ...
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84 views

Change Initramfs script

I made RAID 0 by mdadm'ing partition located on dmraid VIA VT6421 and Western Digital hdd. Installed Ubuntu on that RAID. Now, when I boot, I get (initramfs) ash prompt. There, I have to write mdadm ...
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4k 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 ...
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Change numbers in the Number column to be consecutive from 0 for an mdadm RAID array

I have a RAID 1 array: # mdadm --detail /dev/md0 /dev/md0: Version : 1.2 Creation Time : Thu Oct 18 21:52:43 2012 Raid Level : raid1 Array Size : 1048564 (1024.16 MiB 1073.73 MB) ...