Questions tagged [block-device]

Block devices are a specific type of Unix device node, typically representing storage devices such as hard drives, CD-ROMs, etc.

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Is devicemapper linear not just passthrough?

I'm trying to follow the script in https://jvns.ca/blog/2021/01/27/day-47--using-device-mapper-to-manage-firecracker-images/?hmsr=joyk.com&utm_source=joyk.com&utm_medium=referral but getting ...
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How to deal with dynamic drive name when device mounting hard drives to LXC on Proxmox?

Question Setup On a Proxmox server I create an LXC container with: pct create 101 local:vztmpl/centos-8-default_20201210_amd64.tar.xz --features mknod=1,nesting=1,fuse=1 --ostype centos --storage=CTVM ...
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Can Block Device IDs in LVM be set statically?

I have a system using LVM2 with a single PV which contains 1 VG which in-turn contains 5 logical volumes (/, /home, /var, /swap, /data). When I create a snapshot of LV / (lvcreate -L 15G -s -n ...
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How can i test my SAS Controller card? [closed]

I am in need of testing my Dell SAS Controller card. I am seeing too many errors on a Raidz2 installation, since last July, than to possibly be true. Its as if one drive after another keeps spinning-...
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AWS: Can't mount my restored volume (EBS snapshot)

I restored an EBS volume from AWS Backup and attached it to a new EC2 instance. When I lsblk I can see it under the name /dev/nvme1n1. More specifically the output of lsblk is: NAME MAJ:MIN RM ...
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Factually Btrfs is it suitable for block storage usage?

It exists various storage device, file, block and object based. Some filesystem are dedicated to a kind of device. what about Btrfs ? Here I would like to get some technical facts about Btrfs over a ...
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Using MySQL raw disk on Windows?

I'm having trouble getting MySQL 5.7 to use raw disk (a block device, bypassing the filesystem) for its data. My understanding of the documentation is that basically, first time mysqld is executed, ...
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lsblk shows LVM volume as subcomponent of a partition

Given two physical drives, sda and sdb, I have: Used fdisk to make sda1, sda2, sdb1 and sdb2 Created four physical volumes accordingly: pvcreate /dev/sda1 etc Created a volume group: vgcreate datavg /...
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Doesn't file storage rely on block storage?

I'm usually working on software and am weak on storage. I'm reading about block vs file vs object storage and everything I find talks about storage as an entirely isolated subject rather than ...
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Block Storage Metadata

What is the Metadata stored with file and block storage? I assume that file storage has metadata regarding to the hierarchical nature of file system like,what files,what directories,files/sub-...
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Filesystem for a shared block device for a linux

Is there such a thing? I don't care about performance, I just need to be able to have access to the same block device from two computers. The block device does not have anything fancy (like ...
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AWS Device names; /dev/xvda

I kind of know that sda comes from SCSI device from early Unix/Linux days. However, I had some trouble when I was playing around with detaching/attaching Volumes to my AWS EC2 Instances. What I ...
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Looking for a NBD C/S for windows (Network Block Device) [closed]

Where can I find a NBD Server (and also a Client) that I can use in windows 10? (preferably FOSS source code for inspect/change/compile/...) Been looking for a while on the internet and seems that no ...
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I had some drbd (i guess block devices?) on my server, after a crash they are all gone

I am not a sys admin but inherited some servers setup with no documentation in linux. Today the server died in a way it was unresponsive and the VMs running on it down...after a good few hours the ...
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How to map a UUID directly to both a device name (e.g. /dev/sda1) AND a mount point (e.g. /mnt/home2)?

I know how to map /etc/fstab to the mount point with the device name: /dev/sdb1 /mnt/home2 ext4 usrjquota=quota.user,jqfmt=vfsv0 0 0 This practice is however highly ...
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In CentOS 7, is there a way to specify which block devices should be tuned with the scheduler (or ELEVATOR)?

In CentOS 6, there was /etc/tune-profiles/my-server/ktune.sysconfig with this text(I'm referring to the comments that explain what the code is doing): # This is the I/O scheduler ktune will use. ...
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How to retain blockdev changes after server restart?

I am setting block device read ahead buffer size like so: blockdev --setra 8192 /dev/sda As suggested here. The problem is after restart it goes back to 256 (default). I need it to retain the value ...
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Find mount point by device UUID

I have device UUID like from blkid: /dev/sda1: UUID="5db99adc-11d3-482d-af80-1985dac704b1" TYPE="ext4" PARTUUID="000f2b58-01" I search a tool which I can give 5db99adc-11d3-482d-af80-1985dac704b1, ...
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Dont use /dev/sd* for removable device

Today I almost erased my system with dd because I was going to write on my internal HDD (/dev/sdb*) instead of the removable usb (/dev/sdc*). I want to make a udev rule to set any block usb under a ...
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Btrfs check repair give device busy. How to see what it keeps busy?

I am in a chicken-egg situation for my secondary harddrive (non boot): My BTRFS mount has gone readonly because no space left. btrfs filesystem resize only works on mounted volumes. I needed to ...
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Hard drive not visible during Linux Mint installation

I had successfully installed Linux Mint 19 on my new Dell laptop at work. It was working fine, in general, though it did not shut down properly. I'd seen somewhere a video driver might be responsible, ...
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Documented size of Linux kernel partition sector size in bytes

My primary question is to authoritatively see if the block size used in sector counts: /sys/block/<disk>/<partition>/size is in fact 512 B, or if this can vary. I thought this would be ...
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How to tell if linux disk is READ ONLY

I have a sata disk on module which has a hardware switch which can lock the disk from being written in a READ ONLY MODE. Is there a way to tell in software whether or not that switch has been switched ...
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Why is there both character device and block device for nvme?

I am trying to understand the configuration of nvme. But I do not understand why there are two devices: nvme block and nvme character device: crw------- 1 root root 243, 0 Dec 12 16:09 /dev/nvme0 ...
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Cannot format a drive once used in a ZFS pool

I have created a ZFS test pool with a drive - now I have pulled thet drive out and want to format it to EXT4 and use it outside of ZFS. I think the pool wasn't properly destroyed. Now when I plug the ...
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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: # ...
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why list of disks not printed with order from sfdisk or fdisk commands

we notice about this problem in last few days on one redhat machine ( version 7.2 ) we notice that order of the disks isn't according to the right order note - sda is the OS instead to get the ...
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Understanding stat, du and ls -l output on my nfs mount

ls -l f.txt -rwxrwxr-x 1 abc abc 1161 Sep 1 02:02 f.txt stat f.txt File: `f.txt' Size: 1161 Blocks: 34 IO Block: 524288 regular file Device: 38h/56d Inode: 6448956669 Links: 1 ...
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Read Ahead value automatically getting updated at boot

OS version: CentOS Linux release 7.2.1511 (Core) I have the following commands in my rc.local file: /usr/sbin/blockdev --report > /root/test_boot /usr/sbin/blockdev --setra 256 /dev/vdb /usr/sbin/...
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How to know if some data already exists on a device disk?

The simple way to check if disk include filesystem is to do: mount /grid/sdb /mnt and if sdb or other /dev/sdx have file-system then mount will be succeeded, if not. Probably file system exists! ...
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cat /dev/zero | pv > /dev/null [closed]

cat /dev/zero | pv > /dev/null What exactly happens here and what determines the speed of this process. Even on low end hardware you get a couple of GB/s transfer speeds like this.
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GCE Persistent Disk block sized writes data integrity

The block size for a SSD Persistent Disk appears to be 4096 bytes. If I write aligned blocks of 4096 bytes directly to the block device (/dev/sdb with O_DIRECT and posix_memalign), are these writes ...
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USB Mass Storage recognized, but SCSI block-device not showing up

The block-device of a USB mass storage does not show up in Ubuntu 16.04, while I positively can see it in Ubuntu 14.04. Question: How can I make it show up in Ubuntu 16.04? NOTES: Both machines are ...
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5 votes
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Tool to visualize linux block devices (partitions, LVM PVs, LVs, mdadm devices...)

I'm looking for a tool that will scan my GUI-less server and create an easy to digest rough overview of all the block devices and their relationship (disk partitions, mdadm devices, LVM PVs & LVs ...
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How to query DRBD device size?

To write Ansible script to setup DRBD device and file systems, I face the following issue: # blockdev --report /dev/drbd0 RO RA SSZ BSZ StartSec Size Device blockdev: cannot ...
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Give a VM access to a whole disk with the least overhead with qemu-kvm

I'm moving a Windows 10 install from dedicated hardware to a KVM VM. The disk (SSD) is being physically moved from the current machine to the VM host machine. Is there a way to just pass the entire ...
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Why is an EC2 AWS instance showing an extra block device?

I'm using aws cli's autoscaling to create EC2 instances. Despite only having two device mappings in my launch config, the resulting instances have an additional device. The pertinent map Json: "...
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No w/s in iostat output even though wMB/s is high

I am trying to format a 2 TB SAN based block device (/dev/mapper/mpathb). Even though, mke2fs has been running since over one hour without completing, iostat -z -x -m 10 output in a separate terminal ...
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Units for size in /proc/partitions don't make sense

I have a Seagate 750GB drive. Parted shows the drive as 750GB parted /dev/sdc print Model: ST375064 0AS (scsi) Disk /dev/sdc: 750GB Sector size (logical/physical): 512B/512B Partition Table: gpt ...
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Is there a standard file extension for block device image files

Block device image files are just a large contiguous set of blocks for the device they are emulating. I realize that file extensions are more for the user and that generally on Linux operating systems ...
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Where does blkid get its information from? (/dev/block/ showing up in blkid output)

I have a CentOS 7 box that is acting very strangely. On first boot, typing "blkid" produces: [BurnC7 (2015-12-17 22:00:25) ~]# blkid /dev/block/8:3: UUID="c83f7479-4bc1-44e5-84ae-e38a83e75219" TYPE="...
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How to tell mdadm to use a partition as/instead of a block-device?

I have four 500GB disks which were set up as a Linux Software-RAID 5 volume during the Debian install (next to the system drive which is a SSD). One of the drives (sda) went bad and now I am trying to ...
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Proper way to identify member devices in mdadm.conf

My current mdadm.conf looks like: $ cat /etc/mdadm/mdadm.conf DEVICE /dev/sdb1 /dev/sdc1 ARRAY /dev/md0 metadata=1.2 spares=0 UUID=357ff7cc:55e78d18:9fc7917b:f5b253f2 MAILADDR me@example.com Since ...
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Is there a way of relating the RAID units with the OS devices in 3ware?

I got a Linux server recently with a 3ware RAID. It has several volumes (/c4/u*/v*) that are seen by the OS as devices (/dev/sd*) I can roughly relate those units with the devices because of their ...
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How to have automatic file system checks for Linux Software Raid?

In a Linux Software raid, what is the best practice for periodically having the filesystems checked? With single drive or hardware raid, tune2fs -c 5 -i 1w /dev/sda1 means check the filesystem every ...
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Why is my HDD partition a character special device?

I have a bunch of old 1T disks with an mdadm array on them. They had been out of commission for awhile, but yesterday I slotted them into a server running an up to date Debian Jessie. Eventually I ...
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Readahead for /var/lib/mongo is set to 4096KB

I'm trying to set the readahead for mongo 256 or less as recommended, I looked at the documentation for any guidance and I found this: Ensure that readahead settings for the block devices that ...
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Is it possible to calculate where is, physically, a bad block located on a hard disk?

I dd_rescue'd a hard drive, and I know where the bad blocks are. I still have the drive with me, so I can get any information needed from SMART or fdisk. I would like to know if it is possible to see,...
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XenServer move VM Failed

We currently are running our XenServer virtual machines off of an over extended Drobo unit and wanted to migrate a particular 600+GB VM off of the Drobo onto a newer Drobo, so I attached a storage ...
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Whole block device named xvda1, xvda2 instead of xvda, xvdb

I am working on a VM that was set up for me in a public cloud. It's running under the Xen hypervisor in paravirtualized mode and has two virtual disks. So I expect the virtual disk block devices to be ...
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