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1answer
153 views

What is /dev/mapper/cachedev1?

I just got my first QNAP NAS, used to work mostly with Synology before, and I'm currently trying to figure out how the system uses LVM. Mostly out of curiosity. In my specific case, it's a 2 bay NAS ...
0
votes
0answers
189 views

I/O queue on LVM device v.s. I/O queue on underlying device(s)

dm-1 / alan_dell_2016-swap is an LVM Logical Volume, which is physically stored on partition sda7 of the device sda. NAME MAJ:MIN RM SIZE RO TYPE MOUNTPOINT sda ...
0
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1answer
1k views

How to take space from one VG and add it to another?

I've seen that /dev/mapper/VGP4--CHK-LVP4--CHK is running out of space. I would like to increase this. Filesystem Size Used Avail Use% Mounted on udev ...
2
votes
2answers
368 views

LVM volume on USB drive fails: Read-only file system

This is on a Raspberry Pi running Raspbian 8 (Linux kernel 4.9.) I have a 64 GB USB pen drive plugged (as /dev/sda) and configured as an LVM physical volume. There's only one volume group ("data") and ...
1
vote
1answer
461 views

After increasing chunksize in an LVM cache, files are no longer promoted to the cache

After running into issues with running out of kernel memory, I increased the chunksize of my lvmcache from the default (which I believe was 64k) to a much higher 8M. After this change, blocks do not ...
2
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0answers
510 views

create a device-mapper snapshot of an lvm volume multiple linear device with cow data outside of volume group

I need to make an in-memory snapshot of a running mounted root filesystem. The filesystem itself is on an lvm device, but there is zero free space in the VG and there is no way to expand it. However ...
2
votes
0answers
65 views

recover last state of full lvm snapshot

I recently ran into the case that an LVM snapshot overflowed. The reasons are unclear: * there was probably no write access to the origin at all * both snapshot and origin have same size (100g, 25600 ...
4
votes
2answers
5k views

What's the difference between lvmcache and dm-cache?

Recently I found article mentioning that recently dm-cache significantly improved in linux. I also found that in userspace you see it as lvmcache. And it's quite confusing for me. I thought that LVM ...
1
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1answer
295 views

Does lvm-thin use dm-thin underneath or they are completely separate utilities?

LVM snapshots seem to have extremely poor performance It seems that dm-thin snapshots use a new implementation: Another significant feature is support for an arbitrary depth of recursive ...
1
vote
1answer
475 views

How to handle (with LVM or DM (device mapper)) when a drive has gone away and come back as a new block device

(This correct answer is to one that bears little surface resemblance to this one. Asking the question and answering it myself with reference to that one.) Consider a virtual host environment in which ...
4
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1answer
2k views

Cannot mount LVMm: resume ioctl on failed

I wanted to resize my LVM, followed some tutorial on the net and the system totally crashed (I got some boot error with UUID not found). I ran a LiveCD and tried to at least recover some files but I ...
13
votes
1answer
2k views

Why are there two different values for the size of a drive and how to reconcile them with device-mapper and LVM?

I have a 1 TB drive attached via USB. It contains an LVM physical volume filling the entire device (without any partition table). When I tried to extend a logical volume by using the entire PV, the ...
4
votes
2answers
11k views

device mapper on RHEL6 unable to create devs for LVM logical volume

I have XEN guest running RHEL6, and it has a LUN presented from the Dom0. This contains an LVM volume groups called vg_ALHINT (INT for Integration and ALH is an abbreviation of its Oracle database ...
1
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0answers
1k views

dm snapshot - how does it work?

Fedora uses dm-snapshot for making the root filesystem read-write. At least for me, when running a livecd (even without touching it), it will become unusable relatively quickly meaning it has ...
1
vote
1answer
755 views

Can we create lvm volume group with mapped device?

I can create a lvm volume group with a loop device. But if I use dmsetup to map the loop device into several devices, then I can't create a lvm group with /dev/dm-. Why is it not possible to create ...
4
votes
3answers
21k views

list the devices associated with logical volumes without using lvm2 package commands

I want to list all the physical volume associated with logical volume. I know lvdisplay, pvscan, pvdisplay -m could do the job. but I don't want to use these commands. Is there any other way to do it ...