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This HOWTO describes how to use Software RAID under Linux.

Mdadm Cheat Sheet

Mdadm is the modern tool most Linux distributions use these days to manage software RAIDarrays; in the past raidtools was the tool we have used for this. This cheat sheet will show the most common usages of mdadm to manage software raid arrays; it assumes you have a good understanding of software RAID and Linux  Full Article…

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How to Configure Software RAID on Linux ?

Software RAID is one of the greatest feature in Linux to protect the data from disk failure.We have LVM also in Linux to configure mirrored volumes but Software RAID  recovery is much easier in disk failures compare to Linux LVM. I have seen some of the environments are configured with Software RAID and LVM (Volume groups are built using RAID devices).Using  Full Article…

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How to scan new FC LUNS and SCSI disks in Linux ?

Scanning FC-LUN’s in Redhat Linux 1.First find out how many disks are visible in “fdisk -l” . # fdisk -l 2>/dev/null | egrep ‘^Disk’ | egrep -v ‘dm-‘ | wc -l 2.Find out how many host bus adapter configured in the Linux box.you can use “systool -fc_host -v” to verify available FC in the system.  Full Article…

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Rescanning your SCSI bus to see new storage

If you have added new storage to a running VM, you probably won’t see it. This is because the SCSI bus to which the storage devices are connected needs to be rescanned to make the new hardware visible. How you rescan the SCSI bus depends on the operating system your Virtual Machine is running. Instructions  Full Article…

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Linux Software Raid 1 Setup

1. Introduction This article describes step by step setup of Linux software RAID 1 on Linux Platform. Although this software RAID 1 configuration has been accomplished on Debian ( Ubuntu ) it also can guide you if you are running some other Linux distributions such as RedHat, Fedora , Suse, PCLinux0S etc. For RAID-1 setup we  Full Article…

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sfdisk

On a non GPT partition table I can do sfdisk -d /dev/sda | sfdisk /dev/sdb. But sfdisk doesn’t support GPT partition tables. What can I use instead? Install gdisk which is available in the Ubuntu Universe repositories. Then use the sgdisk command (man page here) to replicate the partition table: sgdisk -R /dev/sdY /dev/sdX sgdisk  Full Article…

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How Does a Raid 10 Array Work

If you need to implement a storage solution that supports I/O-intensive operations (such as database, email, and web servers), RAID 10 is the way to go. Let me show you why. Let’s refer to the below image. Imagine a file that is composed of blocks A, B, C, D, E, and F in the above  Full Article…

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create a software RAID-1 array with mdadm

Redundant Array of Independent Disks (RAID) is a storage technology that combines multiple hard disks into a single logical unit to provide fault-tolerance and/or improve disk I/O performance. Depending on how data is stored in an array of disks (e.g., with striping, mirroring, parity, or any combination thereof), different RAID levels are defined (e.g., RAID-0,  Full Article…

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Manage software RAID arrays

1. Create a new RAID array Create (mdadm –create) is used to create a new array: 1 mdadm –create –verbose /dev/md0 –level=1 /dev/sda1 /dev/sdb2 or using the compact notation: 1 mdadm -Cv /dev/md0 -l1 -n2 /dev/sd[ab]1 2. /etc/mdadm.conf /etc/mdadm.conf or /etc/mdadm/mdadm.conf (on debian) is the main configuration file for mdadm. After we create our RAID  Full Article…

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Mdadm: A New Tool For Linux Software RAID Management

raidtools has been the standard software RAID management package for Linux since the inception of the software RAID driver. Over the years, raidtools have proven cumbersome to use, mostly because they rely on a configuration file (/etc/raidtab) that is difficult to maintain, and partly because its features are limited. In August 2001, Neil Brown, a software  Full Article…

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How to Use MDADM Linux Raid

Create a 6 drive raid 5 array called /dev/md0 with chunk size of 16384: (typically, bigger chunk sizes are better for bigger files, default is 512) mdadm –create –level=5 –chunk=16384–raid-devices=6 /dev/md0 /dev/sdb /dev/sdc /dev/sdd /dev/sde /dev/sdf /dev/sdg Assemble raid array that is not in the config file: mdadm –assemble /dev/md0 /dev/sdb /dev/sdc /dev/sdd /dev/sde /dev/sdf  Full Article…

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mdadm cheat sheet

create a new array mdadm –create /dev/md0 –level=1 –raid-devices=2 /dev/sda1 /dev/sdb1 or… mdadm -C /dev/md0 -l1 -n2 /dev/sd[ab]1   add array to the configuration file: mdadm –detail –scan >> /etc/mdadm.conf or on debian (sigh)… mdadm –detail –scan >> /etc/mdadm/mdadm.conf   can only remove failed disks from an array, so fail a disk: mdadm –fail /dev/md0  Full Article…

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