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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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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collectl vs strace - reported block io read/write size

I've got an xfs mount with standard settings (it's an AWS host): [root@host ~]# xfs_info /dev/xvda1 meta-data=/dev/xvda1 isize=256 agcount=4, agsize=524224 blks = ...
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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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198 views

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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202 views

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 store ...
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1answer
358 views

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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531 views

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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1answer
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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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543 views

How to auto mount 2nd drive on boot in Windows Azure on linux?

I'm currently programming a website and it's connecting to Ubuntu 12.04 linux VM on Windows Azure for database connections. The issue I'm having is that if the VM is restarted the attached disk I ...
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Partition block size different from device's and stacked LVM volumes ones

I have a pair of HP ML350 G6 servers with LSI MegaRAID 9266-4i+CacheVault driving Supermicro CSE836E16 enclosures via SAS bracket, filled with WD RE 3TB SATA drives. On these are configured a RAID10 ...
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240 views

Linux device names: What other non-standard storage device names are there apart from /dev/cciss

This is a question about Linux storage device names on RHEL5 and RHEL6 Most storage devices are accessible using device names /dev/sda, /dev/sdb, etc. By storage device I mean a device that could be ...
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111 views

Copy tape device files

I've just exchanged tape drives between machines (both Unix Tru64). The device files aren't working now, and I have to do some work with them (will generate a different question). I created a ...
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1answer
726 views

Multi-Generation Snapshots using Device Mapper (Linux)

LVM is an amazingly useful tool, however, it seems to still lack support for snapshotting a drive that is already a snapshot. I made a script to handle this automatically but ran into some troubles. ...
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Intentionally cause an I/O error in Linux?

Is there anyway, with Linux, to purposely cause a block device to report an I/O error, or possibly simulate one for testing purposes?
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Are blocks that are read from LVM kept in Linux's block cache?

Does Linux keep blocks that are read from an LVM logical volume in the block cache as it does with blocks read from a "regular" block device or is the IO direct? Also, do the usual buffering ...
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Possible to set size of ram disk?

When I do yum install MAKEDEV MAKEDEV ram fdisk -l /dev/ram I get the that it is 16MB. I am using MAKEDEV to get a block-device instead of tmpfs. Question Is it possible to set it to e.g. 1GB?
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Scanning for new disks attached using virtio?

I can successfully attach disks to a running KVM instance using virsh attach-disk... virsh attach-disk node-1 /dev/vg_lunsr/lun1 vdb Disk attached successfully ...but these new devices aren't seen ...
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Accessing the partitions on an LVM volume

Suppose you have an LVM volume /dev/vg0/mylv. You have presented this as a virtual disk to a virtualised or emulated guest system. During installation the guest system sees it as /dev/sda and ...
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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 ...
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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 ...
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612 views

Making NFS behave like a block device

We're currently working on a virtualization setup, and because of features like being able to grow volumes on our filers rather than having to go through the process resizing block devices etc. we'd ...
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Is DRBD the only viable block replication solution for Linux?

I've found myself needing redundant storage at a block level. File-level replication (Gluster, GFS, etc) does not work for my use case. It looks like DRBD is the go-to solution for block replication....
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Xen 4.1 host (dom0) with blktap disks (“tap:aio:”) not connecting

Problem using blktap with xen-4.1 running Ubuntu Precise stock kernel with dom0 xen-4.1. I get: [ 5.580106] XENBUS: Waiting for devices to initialise: 295s...290s. ... [ 300.580288] XENBUS: ...
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Seeking distributed, fault-tolerant, networked block storage [closed]

I'm looking for a distributed, fault-tolerant network storage system which exposes block devices (not filesystems) on the clients. A client's block device should write simultaneously to several ...
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213 views

export block device over network without root

I'm trying to export a file as a block device over the network. I do not have root access on the machine where the file exists. I do have root access on the machine(s) where I will mount the block ...
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Create variable sized RAM-backed file systems (Ext4 and Btrfs)

For benchmarking purposes I need to format and mount variable sized ram-backed block devices with Ext4 and Btrfs. Unfortunately the only solution I have come across uses ramdisks which seem to be ...
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FS/disk snapshots (like LVM) with shared cache

On Linux, is there a way to take copy-on-write snapshots of a file system (at the FS, block device, or whatever layer), such that if a copy and another copy/the original are concurrently mounted, the ...
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How to determine the block device booted from in a shell script?

I'm crafting up a shell script (to be called by cron) that runs smartctl on the booted disk on a weekly basis. Is there a fairly universal way to determine what the boot block device is (IE - /dev/sda,...
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385 views

Store QEMU images in database

I have a task to store QEMU images in a database and thinking towards developing of the custom block device. Is this a good idea? Where is it better to start from?
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Force block device (NBD) to bypass the buffer cache

I'd like to know if there is a way to force a block device to bypass the linux buffer cache (ie direct IO) and pass the requests directly to the underlying layer. I know one can open a file using ...
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Quickest way to determine size of a block device?

I've a remote script that checks for some parameters from lvm volumes. One of the things I need to know is the size. I am currently using this: lvdisplay /dev/virtuals/volume_name -C -o lv_size ...