A linux utility used to manage software RAID devices.

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Is it safe to disable write barriers for mdadm RAID?

When configuring RAID 1 or 10 with mdadm, is it safe to disable OS write barriers (with barrier=0 or nobarrier)? As there is no writeback cache memory on software RAID.
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How can SSD write performance be dramatically different on two identical servers?

I am renting two identical physical servers (at Serverloft). These servers come with 2x512 GB SSD disks, and I've set them up with mdadm in a RAID1. The disks are locally installed in the server. The ...
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26 views

Drop in write performance when mirroring two RAID 0 arrays

On a CentOS 7 server with 4 SSDs, I created two RAID 0 arrays with mdadm. Both were formatted with ext4 and mounted on separate directories. I benchmarked them using fio and got the following results ...
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How to create imsm metadata raid1 using mdadm and skip initialisation

I am trying to use --assume-clean option to speed up raid1 creation, using these commands: mdadm --create /dev/md/imsm /dev/sd[c-d] --raid-devices 2 --metadata=imsm --assume-clean mdadm --create ...
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2k views

mdadm: hot remove failed for…

My RAID1 is degraded and I need to replace /dev/sdb. However, I could mark /dev/sdb5 (in /dev/md1) as failed and removed it, but I can't do the same with /dev/sdb1 (/dev/md0 which is mounted on /): ...
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How to interrupt software raid resync?

I want to interrupt a running resync operation on a debian squeeze software raid. (This is the regular scheduled compare resync. The raid array is still clean in such a case. Do not confuse this with ...
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mdadm raid 1 ssd (ata1.00: failed command: READ FPDMA QUEUED - ata1: hard resetting link)

system: Centos 6.7 2.6.32-573.12.1.el6.x86_64 motherboard ASUS P6X58D-E Two ssd: hdparm -I /dev/sda /dev/sda: ATA device, with non-removable media Model Number: TS128GSSD340K ...
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25 views

mdadm scaling beyond 6 disks w/ ssd's

It seems Linux mdadm produces less writes & iops as more disks are added to an array. For example, I have tested the following configurations, with the defaults aside from changing the I/O ...
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37 views

mdadm --grow power failure, /dev/md2 no longer detected, RAID5

Did a terrible stupid mistake. Please advise me how should I best proceed. My configuration is a RAID5 of 4x4TB drives. On top of it, LVM with various partitions including /, swap, everything. The ...
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1k views

Resize openSUSE 12.3 GPT ext4 partitions in a RAID1 disk array

I have a software raid configured (/dev/md2) which has assigned the partitions sda3 and sdb3 from two 3TB disks (sda and sdb). The partition types are GPT not LVM and file system is ext4. Now, the ...
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RAID not changing write speeds [migrated]

So I have two hard drives one connect with SATA and one with USB3.0 SATA (/dev/sdc1): Apple HDD Toshiba USB (/dev/sde2): Western Digital Technologies, Inc. Elements SE Portable ...
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1k views

mdadm: Which disk is being rebuilt?

I noticed my software RAID1 degraded, and wanted to figure out which of the two disks in the array is being rebuilt/re-synced since they both show as being up. I am hoping someone can shed some light ...
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11k views

mdadm Boot Error, incrementally starting raid array Ubuntu SErver 14.04

i build a small Server with Ubuntu 14.04 for Samba, I has one SSD Drive (the ubuntu installation is on it) and 2 3TB SATA Disk, the sata disk are combined to a Raid 1 with mdadm. Now sometimes (no ...
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28 views

GPT, grub and mdadm. sda drive replaced, raid rebuilt in recovery mode, but now server won't boot

This is how partition table loooks like: (parted) print Model: ATA TOSHIBA DT01ACA2 (scsi) Disk /dev/sda: 2000GB Sector size ...
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1answer
79 views

SSD DD write speed lower than HDD [closed]

I've come across a strange phenomena with a new dedicated server that's been provisioned. The server has 2x1TB HDDs in software RAID 1 and a separate 120GB SSD that is intended to be used as a ...
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27 views

Confusion on how to hotswap dm-x device in software raid

Below is the dump when I do lsblk cat /proc/mdstat lmsetup -ls. So sde is dying and I would like to replace it. What i'm confused is, in lsblk it shows sde is part of md3 (software raid). but when I ...
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mdadm - stuck reshape operation

I have a 3 disk RAID 5 array that I tried to add a 4th disk to. mdadm --add /dev/md6 /dev/sdb1 mdadm --grow --raid-devices=4 /dev/md6 This operation started successfully and proceeded until it hit ...
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2k views

Cannot install grub, segmentation fault, unable to identify filesystem, superfluous RAID member, found two disks with same index — Debian 7

A server was recently transported from location A to B, a long journey that took six months. Things have gone wrong due to nothing being labeled prior to shipment. Yes, I know --- it was done by ...
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Can I increase the read error threshold on Linux software raid?

I have a two RAID 10 volumes where only one partition on /dev/sda was kicked out of one of the two volumes. Here's /dev/mdstat (in the middle of recovery): md1 : active raid10 sda3[4] sdd3[3] ...
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30 views

Raid device on rename appended with _0

I am creating various raid configurations. When I create a raid device say 5 with 3 disks mdadm --create /dev/md/md5 --level=5 --raid-devices=3 /dev/sda /dev/sdb /dev/sdc It does create a device ...
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18 views

Server rollbacked after apt-get upgrade and a restart

Today I was trying to find out why my server stalled after certain amount of requests on apache2, but couldn't figure why, so I decided to upgrade it(apt-get update & apt-get upgrade) before I ...
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1answer
141 views

Ubuntu 14.04 Software RAID 1 - md0 inactive

I have my root filesystem on /dev/sdc, and a software RAID 1 spanning /dev/sda and /dev/sdb (I think). I physically moved my computer and ran software updates today (either of these could be the ...
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How to keep md-raid from blocking IO?

I run a server with md-raid (software) level 1 (2 HDDs mirroring) and several different applications run on it. The problem arises when file-intensive jobs (e.g. extracting large archives) run while ...
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2k views

Recover mdadm RAID 10 array: listing all as spares

I'm a bad person and haven't backed up my RAID elsewhere. I now have a RAID10 array that won't assemble, and I'm hopeful I can save it. Here's the details: I have five hard drives set up as RAID10 ...
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RAID10 array lost after reboot | Amazon Linux

I carefully followed this procedure to setup RAID10 on Amazon Linux: https://mongodb-documentation.readthedocs.org/en/latest/ecosystem/tutorial/install-mongodb-on-amazon-ec2.html I also upgraded ...
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Does mdstat showing very different block sizes for identical drives indicate a failing drive?

One of my servers has a RAID1 array composed of two 240GB SSDs. It is managed/controlled via Linux, not via a hardware card. Recently, for no apparent reason, the array needed rebuilding. I rebooted ...
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850 views

Is using nested RAID 6+1+0 a good idea?

Currently I have 24 disks of 500 GB, and I would like to create a bigger nested RAUD using a Dell Power Edge R730 server, having 4 times RAID 6 with six times 500GB each, over them I want to add RAID ...
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38 views

Ubuntu raid - can't boot - mdadm

I was trying to copy the /tmp to another disk (Ubuntu 14.04 server), however after doing so, any command that I typed to the shell started to throw errors. I tried to reboot it, but now it just ...
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32 views

mdadm: replace disk in a 4-disk RAID5 while it resyncs

I'm preparing a server with 4 disks assembled into software RAID5 during Debian 8 installation. Shortly after the system was configured, SMART detected an Offline Uncorrectable Sector error, so I ...
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2k views

mdadm raid5 too slow when writing

I have set up a RAID5 array using 4 disk partition. All disks are 2TB. When the RAID5 array was initially syncing it was too slow. So I did a echo 32768 > /sys/block/md2/md/stripe_cache_size and ...
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Having trouble mounting an mdadm array. Corrupted Filesytem?

I have a server that crashed and won't power on. I don't care about the server, but I'd like to recover the data attached to 2 external usb drives that were mirrored (raid 1) using mdadm. This system ...
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2k views

Linux mdadm software RAID 6 - does it support bit corruption recovery?

Wikipedia says "RAID 2 is the only standard RAID level, other than some implementations of RAID 6, which can automatically recover accurate data from single-bit corruption in data." Does anyone know ...
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8k views

Grub rescue, will not boot from mdadm RAID, no such disk or device — mduuid wrong?

I am running a 14 disk RAID 6 on mdadm behind 2 LSI SAS2008's in JBOD mode (no HW raid) on Debian 7 in BIOS legacy mode. Grub2 is dropping to a rescue shell complaining that "no such device" exists ...
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Which are possible hierarchies for bcache, mdadm RAID and LVM?

Assuming I want to use bcache for caching, mdadm for RAID (1) and LVM for partitioning (and that I don't care that there might be performance drawbacks due to many levels of I/O and device management ...
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1answer
59 views

One disk accessed more than others during md RAID6 rebuild

I am rebuilding one drive of an 8-drive RAID6 (using 'md' Linux software RAID), and have noticed that it doesn't seem to be going as fast as it could, presumably because one of the drives is being ...
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45 views

mdadm not assemble after restart

I have 2 disk with the next structure: lsblk NAME MAJ:MIN RM SIZE RO TYPE MOUNTPOINT sda 8:0 0 3,7T 0 disk ├─sda1 8:1 0 2,7T 0 part └─sda2 8:2 0 931,5G ...
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How to recover XenServer vm's from a mdadm raid 1 HDD

I have an older server, namely, Fujitsu Siemens Primergy TX 150 S6 on witch i have installed XenServer 6.5.0-90233c. On it i have multiple virtual machines of different sizes of witch i need to ...
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11k views

mdadm --zero-superblock on disks with other partitions on them

I have three disks which used to hold an MD RAID5 array. I have since removed (or so I thought) this array and created partions for btrfs and swap space. On rebooting the machine, MD still binds the ...
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4k views

Can you disable automatic mdadm startup?

I am creating a RAID 10 array over four iSCSI targets. I want to control everything manually though so I can run it through heartbeat. I've unlinked the open-iscsi and mdadm scripts from /etc/rc#.d/ ...
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How to backup mdadm RAID superblock info?

I'm Looking for a simple command that will backup the mdadm superblocks on a RAID volume. A quick way to scan you system would be: mdadm --examine /dev/sd[a-z]* > raid-volumes.txt Now after ...
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17k views

Recover RAID 5 data after created new array instead of re-using

Folks please help - I am a newb with a major headache at hand (perfect storm situation). I have a 3 1tb hdd on my ubuntu 11.04 configured as software raid 5. The data had been copied weekly onto ...
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Can't stop and reformat /dev/md0

I want to reformat /dev/md0, which is a RAID0 array consisting of 4 disks (sd[bcde]). However, when I tried to run the command mke2fs, I received the following error message: /dev/md0 is apparently ...
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60 views

Unexpected discrepancy between write and read performance using cryptsetup 1.4.3 and 1.6.6 on Debian Wheezy (7.9) and Debian Jessie (8.2)

I have been setting up a raid1 array and have set up an encrypted medium using cryptsetup with default options. The raid arrays are supposed to use 2 drives, but for the moment, I only have 1 drive in ...
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3k views

Cant boot newly created mdadm software raid in Debian linux squeeze

Hello I have very strange problem creating swraid on Debian Squeeze Linux. I started creating RAID1 from existing standard instalation of Debian on single drive. So I bought new drive and started ...
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777 views

grub on debian wheezy doesn't recognise mdraid

We're having a really strange problem when trying to boot from an mdraid on Debian Wheezy. All references online that I can find tell me that grub 1.99 (which is part of Debian Wheezy) should have no ...
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6k views

Removing raid metadata from drives

Normally when I have a drive which contains raid metadata e.g. from fakeraid or a hardware raid card I can get rid of it with: dmraid -r -E /dev/sdX Or if that doesnt work, doing a simple dd ...
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1k views

Optimizing disk performance on KVM VM configuration

I have a KVM host server running Ubuntu 12.04 LTS, bare bones installation with only KVM installed. The server has an 8 Core Intel(R) Xeon(R) CPU E3-1230 V2 @ 3.30GHz CPU with 32GB of RAM and SATA ...
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169 views

Can't limit mdadm's detection

I've got a problem with mdadm and generating initrd. I had some problems with one disk, so suddenly mdadm started detecting my raid1 arrays to be on hda, hdb2, hdb3 - even though they should really ...
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54 views

Recovering an RAID6 using ddrescue. mdadm: failed to add, invalid argument

I had 3 drives fail in a matter of a week on a RAID6. Luckily, one drive seemed to be mostly fine. I was able to run ddrescue and it copied all but one small area (couldn't read 14MB out of 3TB). ...
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51 views

Mdadm raid1 says the last drive attached has failed

I have a software raid1 array. Today I found one of the drives failed to sync, and I got this: $ cat /proc/mdstat Personalities : [raid1] md0 : active raid1 sdb1[0] sda1[2](F) 153597312 ...