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Questions tagged [device-mapper]

30 questions
20
votes
1 answer

Why higher await time for DM multipath device than underlying device?

We have a CentOS 6.4 based server attached to Hitachi HNAS 3080 storage and observed the kernel remount the filesystem in read-only mode: May 16 07:31:03 GNS3-SRV-CMP-001 kernel: [1259725.675814] EXT3-fs (dm-1): error: remounting filesystem…
pdp
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14
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3 answers

Linux device-mapper maps LVM PV nested inside LV when taking snapshot

Which is really messing with my plan to back up this machine... I have a server which is a KVM hypervisor to several virtual machines. One of these is running Docker. It has its Docker volumes on /dev/vdb, which is set up as an LVM PV, on which…
Michael Hampton
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11
votes
3 answers

kvm to vmware migration - lvm based guest + multipathing

What is recommended way of migrate from kvm to vmware in case of lvm based guest with multipathing? I found that similar questions were already asked few years ago: How to migrate KVM based VMs running in LVM setup to Vmdk images converting KVM…
joe33
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11
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4 answers

is /dev/dm-1 a partition or a whole block device?

Is there a way to figure out if /dev/dm-1 is a block device partition or a whole block device? If /dev/dm-1 is a partition, is there a way to find out the path to the corresponding whole block device?
Loic Dachary
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10
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1 answer

how to correctly 'extend' a linux device mapper partition?

I am missing some concept with linux disk management, I have free space on a single physical volume that I want to to extend an ext4 file-system with, which is a logical volume. I look at fdisk -l - it is a GPT (warnings) Disk /dev/sda: 299.4 GB,…
Sum1sAdmin
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6
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0 answers

cryptsetup cannot close mapped device

When I run: LANG=C cryptsetup --debug luksClose /dev/mapper/Pool-A it fails as follows: device-mapper: remove ioctl on Pool-A failed: Device or resource busy Device /dev/mapper/Pool-A is still in use. Command failed with code 16: Device or…
sebelk
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4
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0 answers

How to disable write barrier on docker thinpooldev?

My server has very low disk performance if write barrier is enabled. As it has a disk controller with battery for the cache it is safe to add the "nobarrier" option to /etc/fstab. This makes a huge difference in performance. I want to the same for…
Peter
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3
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2 answers

multipath, device mapper, and disk i/o scheduler

We have two machines with a multi path SAS controller, each with 12 physical disks attached. We were looking into some I/O speed oddness, and noticed that on one machine, where /dev/mpath/mpath*p1 maps to dm-13 through dm-24 in various ways, dm-13…
Michael Graff
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2 answers

Why is dmsetup failing when I try to create a snapshot?

I would like to create a COW device for an existing block device using dmsetup. The block device is: # blockdev --getsz /dev/loop0 3534848 I am trying to use a 256M ramdisk as the backing store: # blockdev --getsz /dev/zram1 524288 I am using the…
larsks
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1 answer

How to rebuild a dmraid RAID10 array?

Q: How do I force a rebuild? The following describes the scenario. I've been experimenting with forcing a RAID10 to rebuild, so I could see what dmsetup status output should look like when a RAID is rebuilding, and also so I could get some…
Sandra E
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2
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0 answers

Data corruption after dmsetup suspend, reload, resume, and re-suspend

Consider the following series of events for a device-mapper crypt target, test, holding an ext4 filesystem. These three commands swap out the crypt target's table with a new (dummy) table. This changes the encryption key to an invalid one. The…
forest
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2
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0 answers

How to make a virtual disk image out of several parts?

During a process of moving to a virtualized infrastructure I encountered the following curious problem. We want to evaluate everything first. This involves creating a virtual images of all required systems, running them all together in an isolated…
Nikita Kipriyanov
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1
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1 answer

How to modify the "dm-*" value?

As I command multipath -ll, the output show like this. ocr3 (149455400000000000000000001000000ca0200000d000000) dm-9 IET,VIRTUAL-DISK [size=980M][features=0][hwhandler=0] \_ round-robin 0 [prio=0][active] \_ 1:0:0:11 sdo 8:224 [active][ready] \_…
finkfink
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1 answer

Cannot create PV on /dev/dm-NN (/dev/dm-N works)

I'm unable to create PVs on Multipath-Volumes that are available at /dev/dm-NN where N~[0-9] but I can create them on single digit devices like /dev/dm-9: # pvcreate /dev/dm-6 Physical volume "/dev/dm-6" successfully created. # pvcreate…
Fladi
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1 answer

I/O scheduling on LVM on dm-crypt

I have the following setup: Stock Debian stable (Linux kernel 3.16.7) running on Dell PowerEdge R320 Two SATA hard drives in RAID1 on a PERC H310 Mini controller, visible as /dev/sda dm-crypt target dm-0 backed by /dev/sda2 A single LVM volume…
dragonroot
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