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Questions tagged [md]

Multiple Device driver aka Linux Software RAID

77 questions
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Readahead Settings for LVM, Device-Mapper, Software Raid and Block Devices - what wins?

I've been trying to find a straight answer on this one, and it has proved elusive. This question and its answer is close, but does not really give me the specifics I would like. Let's start with what I think I know. If you have a standard block…
Adam C
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How to re-add a drive when RAID is in degraded mode?

I am running an unmanaged Ubuntu server and due to recent performance issue and sent a request to the provider only to receive the following response: "Dear Client, as requested we have checked your drives. Both drives pass a test without any…
captain lizard
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3 answers

Deciphering continuing mpt2sas syslog messages

Summary I have been getting these cryptic messages in syslog since I installed some new hardware and I can't figure out what the problem is, if it's serious, or what to do about it. They're from the new SATA HBA and they follow a pattern. I will get…
Chris Smith
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When adding a new disk to RAID 1, why does it sync unused space?

I recently set up RAID 1 on Linux with mdadm. When adding a new HDD to RAID 1, data started to sync between my drives which is expected. I didn't expect that it started syncing the entire drive, including unused space. The HDDs were 6 TB with only…
idunnololz
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2 answers

How to stop a Linux LVM volume group?

I am currently dealing with a multiple disk failure on a Linux LVM Volume Group that is backed up by a RAID-5 md device. One disk has been taken out completely and another one is showing a limited number of corrupt sectors, due to what seems to have…
thkala
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6
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2 answers

MD RAID sector repair

This article states that RAID controllers are smart about unrecoverable read errors, and try to rewrite such sectors with the redundancy of the component drives. If the sector is bad, the disk's firmware will reallocate the sector…
Halfgaar
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1 answer

What effect does RAID stripe size have on read-ahead settings?

I'm trying to figure out the correct read-ahead values to set on a RAID10 array, and I'm wondering if the RAID stripe size should factor into my considerations. I've heard conflicting information about this in the past. I once heard that you should…
stbrody
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MD RAID - disable NCQ

Why is it recommended in a MD RAID (mdadm) to disable NCQ per-disk? echo 1 > /sys/block/sdX/device/queue_depth I read this tip in many articles regarding RAID tuning but nobody explains why.
Javier Franck
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1 answer

reusing existing RAIDs on preseeded installation

I'm trying to automate the reinstallation process of existing Ubuntu installations. Partition layout: md0( raid1, /dev/sda1#/dev/sdb1 ) - swap (2G) md1( raid1, /dev/sda2#/dev/sdb2 ) - / (20G) md2( raid1, /dev/sda3#/dev/sdb3 ) - PV (remaining…
Frank
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5
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2 answers

Boot failure with root on MD (RAID1) + LVM: udev event timing

A fresh install of Ubuntu Server 13.10 (x64) is having problems booting from its root volume located in md+lvm. I've kludged a solution for now, but I'd like to understand more about what's going on and what better solutions there might be. Since…
strix
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5
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Why does RAID5 with an odd number of data disks have poor write performance

According to the comments on my other question, it's more than possible that the reason my MD RAID array is performing poorly is because my RAID5 array has 5 data disks. I've tried searching for information on why this is, but haven't found…
Matthew Scharley
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1 answer

Debian server has degraded mdadm array on every boot

I have a Debian server with MD raid (2 actives, one spare): Personalities : [raid1] md1 : active raid1 sdc2[0] sdb2[1] sda2[2](S) 1068224 blocks [2/2] [UU] md0 : active raid1 sdc1[2](S) sdb1[1] sda1[0] 487315584 blocks [2/2] [UU] …
Halfgaar
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1 answer

Best way to RAID 4 x Intel SSD 910 for PostgreSQL

I have a Linux (debian/ubuntu) server with 4 x Intel SSD 910 800GB pcie that I need to RAID together. The biggest problem with these card is that they give you 4x200GB drives that you cant hardware-raid (more about that here:…
Linus
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Can I split one RAID1 partition in two?

I have a linux box with CentOS 6.2 and a RAID1 (2x 2Tb) configuration: /dev/md1 -> / (10G) /dev/md2 -> /home (1.9T) I want to split the md2 in two different partitions, so I can get the following configuration: /dev/md1 -> / (10G) /dev/md2 -> /home…
Prosys
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VERY peculiar permission masks, UIDs, GIDs and file names in Linux

I've just booted to find my software RAID 5 in Ubuntu not mounting. When trying to mount it gave me an NFS error (which was confusing). I ran fsck on /dev/md0 and my screen scrolled with fixes for about an hour. It claimed to be complete, however…
SimonJGreen
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