\documentclass[11pt]{article} %Gummi|065|=) \usepackage{xcolor} \usepackage[vcentering,dvips]{geometry} \geometry{papersize={6in,9in},total={4.5in,6.8in}} \title{\textbf{RAID on GnuLinux - Mdadm Reference}} \usepackage{graphicx} \usepackage{caption } \author{Steak Electronics} \date{07/31/19} \begin{document} %\maketitle \textcolor{green!60!blue!70}{ \textbf{RAID on GnuLinux - Mdadm Reference}} %\textbf{Todo} %\tableofcontents \textcolor{green!60!blue!70}{ \section{Overview}} There are a few options for software RAID on Gnu Linux. Among them is BtrFS and ZFS, however today I will focus on using mdadm. This is historically the oldest software raid, therefore should be better vetted, although its performance may be less of that of the first two mentioned - for simple servers, mdadm might be the most stable choice. \textcolor{green!60!blue!70}{ \section{Details}} I've worked with this in setting up some Core 2 Duo PCs, with 2 to 4 Sata HDDs. This will be a reference. Let's begin. \\ \\ \textcolor{green!60!blue!70}{ \subsection{Creation of RAID:}} Will not be covered here (yet). You must create the partition tables. Create the raid with mdadm. mkfs.ext4 on the raid partition. Add mdadm to grub config. Reinstall grub. Details may be provided later. \textcolor{green!60!blue!70}{ \subsection{Details of RAID:}} \begin{verbatim} root@advacoONE:/dev# sudo mdadm -D /dev/md127 /dev/md127: Version : 1.2 Creation Time : Fri Feb 1 01:00:25 2019 Raid Level : raid1 Array Size : 57638912 (54.97 GiB 59.02 GB) Used Dev Size : 57638912 (54.97 GiB 59.02 GB) Raid Devices : 3 Total Devices : 2 Persistence : Superblock is persistent Update Time : Fri Feb 1 02:40:44 2019 State : clean, degraded Active Devices : 2 Working Devices : 2 Failed Devices : 0 Spare Devices : 0 Name : devuan:root UUID : 83a8dc03:802a4129:26322116:c2cfe1d4 Events : 82 Number Major Minor RaidDevice State - 0 0 0 removed 1 8 17 1 active sync /dev/sdb1 2 8 33 2 active sync /dev/sdc1 root@advacoONE:/dev#-- \end{verbatim} so you can see, one was removed (it auto removes, when unplugged) \\ \\ \textcolor{green!60!blue!70}{ \subsection{Add Drive to RAID:}} sudo mdadm --add /dev/md127 /dev/sda1 \\ \\ NOTE2: If you setup 2 hdds, in a raid, and want to add a third, if you just --add, it will show up as a spare... if you do mdadm --grow /dev/md127 -raid-devices=3 then the third might be active sync (what we want) note that the --grow, seems to allow for parameter changes after you have already created the raid. you can also specify the exact same command, raid-devices=3 in the setup of the raid (see install doc). Note that if you lose a drive, you can simply add it. \\ \\ NOTE: don't worry about mkfs.ext4 on the raid members, after initial setup. The RAID will manage that. \\ \\ NOTE: if you have a new drive and need to copy the hdd partition tables: https://unix.stackexchange.com/questions/12986/how-to-copy-the-partition-layout-of-a-whole-disk-using-standard-tools or aka \begin{verbatim} (FOR MBR ONLY) Save: sfdisk -d /dev/sda > part_table Restore: sfdisk /dev/NEWHDD < part_table (FOR GPT:) # Save MBR disks sgdisk --backup=/partitions-backup-$(basename $source).sgdisk $source sgdisk --backup=/partitions-backup-$(basename $dest).sgdisk $dest # Copy $source layout to $dest and regenerate GUIDs sgdisk --replicate=$dest $source sgdisk -G $dest \end{verbatim} \begin{verbatim} root@advacoONE:/dev# mdadm --add /dev/md127 /dev/sda1 mdadm: added /dev/sda1 root@advacoONE:/dev# sudo mdadm -D /dev/md127 /dev/md127: Version : 1.2 Creation Time : Fri Feb 1 01:00:25 2019 Raid Level : raid1 Array Size : 57638912 (54.97 GiB 59.02 GB) Used Dev Size : 57638912 (54.97 GiB 59.02 GB) Raid Devices : 3 Total Devices : 3 Persistence : Superblock is persistent Update Time : Fri Feb 1 02:41:43 2019 State : clean, degraded, recovering Active Devices : 2 Working Devices : 3 Failed Devices : 0 Spare Devices : 1 Rebuild Status : 0% complete Name : devuan:root UUID : 83a8dc03:802a4129:26322116:c2cfe1d4 Events : 92 Number Major Minor RaidDevice State 3 8 1 0 spare rebuilding /dev/sda1 1 8 17 1 active sync /dev/sdb1 2 8 33 2 active sync /dev/sdc1 root@advacoONE:/dev# \end{verbatim} Looks good. \begin{verbatim} Rebuild Status : 6% complete Name : devuan:root UUID : 83a8dc03:802a4129:26322116:c2cfe1d4 Events : 103 Number Major Minor RaidDevice State 3 8 1 0 spare rebuilding /dev/sda1 1 8 17 1 active sync /dev/sdb1 2 8 33 2 active sync /dev/sdc1 \end{verbatim} as it progresses, you see the RAID rebuilding. \begin{verbatim} watch -n1 cat /proc/mdstat Every 1.0s: cat /proc/mdstat advacoONE: Fri Feb 1 02:43:24 2019 Personalities : [raid1] [linear] [multipath] [raid0] [raid6] [raid5] [raid4] [raid10] md127 : active raid1 sda1[3] sdb1[1] sdc1[2] 57638912 blocks super 1.2 [3/2] [_UU] [==>..................] recovery = 11.2% (6471936/57638912) finish=13.2min speed=64324K/sec unused devices: \end{verbatim} \textbf{WARNING:} Reinstall grub on the new drive again as well afterwards. \textcolor{green!60!blue!70}{ \subsection{Email Notifications on mdadm}} Test emails on mdadm.. first configure email however you prefer (i currently use ssmtp, see this link: https://wiki.zoneminder.com/How\_to\_get\_ssmtp\_working\_with\_Zoneminder -- then edit /etc/mdadm/mdadm.conf to have your email in mailaddr then \begin{verbatim} sudo mdadm --monitor --scan --test --oneshot \end{verbatim} should send an email https://ubuntuforums.org/showthread.php?t=1185134 for more details on email sending \textcolor{green!60!blue!70}{ \section{References}} \begin{verbatim} The section about degraded disks https://help.ubuntu.com/lts/serverguide/advanced-installation.html.en General partition tips. https://github.com/zfsonlinux/zfs/wiki/Debian-Stretch-Root-on-ZFS SSMTP email setup: https://wiki.zoneminder.com/How_to_get_ssmtp_working_with_Zoneminder wiki.zoneminder.com/SMS_Notifications \end{verbatim} \end{document}