{"id":3052,"date":"2024-05-23T04:49:55","date_gmt":"2024-05-23T04:49:55","guid":{"rendered":"https:\/\/bigboxhost.com\/blog\/?p=3052"},"modified":"2024-05-23T04:51:00","modified_gmt":"2024-05-23T04:51:00","slug":"how-to-replace-a-failed-hard-drive-in-a-software-raid1-array","status":"publish","type":"post","link":"https:\/\/bigboxhost.com\/blog\/how-to-replace-a-failed-hard-drive-in-a-software-raid1-array\/","title":{"rendered":"How to Replace a Failed Hard Drive in a Software RAID1 Array"},"content":{"rendered":"\n

This guide demonstrates how to remove a failed hard drive from a Linux RAID1 array (software RAID) and add a new hard disk to the RAID1 array without losing data.<\/p>\n\n\n\n

Note:<\/strong> A newer version of this tutorial is available that uses gdisk instead of sfdisk to support GPT partitions.<\/p>\n\n\n\n

Initial Note:<\/h3>\n\n\n\n

In this example I have two hard drives, \/dev\/sda<\/em> and \/dev\/sdb<\/em>, with the partitions \/dev\/sda1<\/em> and \/dev\/sda2<\/em>as well as \/dev\/sdb1<\/em> and \/dev\/sdb2<\/em>.<\/p>\n\n\n\n

\/dev\/sda1<\/em> and \/dev\/sdb1<\/em> make up the RAID1 array \/dev\/md0<\/em>.<\/p>\n\n\n\n

\/dev\/sda2<\/em> and \/dev\/sdb2<\/em> make up the RAID1 array \/dev\/md1<\/em>.<\/p>\n\n\n\n

\/dev\/sda1 + \/dev\/sdb1 = \/dev\/md0<\/code><\/pre>\n\n\n\n
\/dev\/sda2 + \/dev\/sdb2 = \/dev\/md1<\/code><\/pre>\n\n\n\n
\/dev\/sdb<\/em> has failed, and we want to replace it.<\/p>\n\n\n\n
<\/p>\n\n\n\n
Step 1: How to check if a hard disk has failed?<\/h3>\n\n\n\n
If a disk has failed, you will probably find a lot of error messages in the log files, e.g. \/var\/log\/messages<\/em>or \/var\/log\/syslog<\/em>.<\/p>\n\n\n\n
You can also run:<\/p>\n\n\n\n
cat \/proc\/mdstat<\/code><\/pre>\n\n\n\n
and instead of the string [UU]<\/em> you will see [U_]<\/em> if you have a degraded RAID1 array.<\/p>\n\n\n\n
Step 2: Removing the failed disk<\/h3>\n\n\n\n
To remove \/dev\/sdb<\/em>, we will mark \/dev\/sdb1<\/em> and \/dev\/sdb2<\/em> as failed and remove them from their respective RAID arrays (\/dev\/md0<\/em> and \/dev\/md1<\/em>).<\/p>\n\n\n\n
First we mark \/dev\/sdb1<\/em> as failed:<\/p>\n\n\n\n
mdadm --manage \/dev\/md0 --fail \/dev\/sdb1<\/code><\/pre>\n\n\n\n
The output of<\/p>\n\n\n\n
cat \/proc\/mdstat<\/code><\/pre>\n\n\n\n
should look like this:<\/p>\n\n\n\n
server1:~# cat \/proc\/mdstat
Personalities : [linear] [multipath] [raid0] [raid1] [raid5] [raid4] [raid6] [raid10]
md0 : active raid1 sda1[0] sdb1[2](F)
      24418688 blocks [2\/1] [U_]
 
md1 : active raid1 sda2[0] sdb2[1]
      24418688 blocks [2\/2] [UU]
 
unused devices: <none><\/code><\/pre>\n\n\n\n
Then we remove \/dev\/sdb1<\/em> from \/dev\/md0<\/em>:<\/p>\n\n\n\n
mdadm --manage \/dev\/md0 --remove \/dev\/sdb1<\/code><\/pre>\n\n\n\n
The output should be like this:<\/p>\n\n\n\n
server1:~# mdadm --manage \/dev\/md0 --remove \/dev\/sdb1
mdadm: hot removed \/dev\/sdb1<\/code><\/pre>\n\n\n\n
And<\/p>\n\n\n\n
cat \/proc\/mdstat<\/code><\/pre>\n\n\n\n
should show this:<\/p>\n\n\n\n
server1:~# cat \/proc\/mdstat
Personalities : [linear] [multipath] [raid0] [raid1] [raid5] [raid4] [raid6] [raid10]
md0 : active raid1 sda1[0]
      24418688 blocks [2\/1] [U_]
 
md1 : active raid1 sda2[0] sdb2[1]
      24418688 blocks [2\/2] [UU]
 
unused devices: <none><\/code><\/pre>\n\n\n\n
Now we do the same steps again for \/dev\/sdb2<\/em> (which is part of \/dev\/md1<\/em>):<\/p>\n\n\n\n
mdadm --manage \/dev\/md1 --fail \/dev\/sdb2<\/code><\/pre>\n\n\n\n
cat \/proc\/mdstat<\/code><\/pre>\n\n\n\n
server1:~# cat \/proc\/mdstat
Personalities : [linear] [multipath] [raid0] [raid1] [raid5] [raid4] [raid6] [raid10]
md0 : active raid1 sda1[0]
      24418688 blocks [2\/1] [U_]
 
md1 : active raid1 sda2[0] sdb2[2](F)
      24418688 blocks [2\/1] [U_]
 
unused devices: <none><\/code><\/pre>\n\n\n\n
mdadm --manage \/dev\/md1 --remove \/dev\/sdb2<\/code><\/pre>\n\n\n\n
server1:~# mdadm --manage \/dev\/md1 --remove \/dev\/sdb2
mdadm: hot removed \/dev\/sdb2<\/code><\/pre>\n\n\n\n
cat \/proc\/mdstat<\/code><\/pre>\n\n\n\n
server1:~# cat \/proc\/mdstat
Personalities : [linear] [multipath] [raid0] [raid1] [raid5] [raid4] [raid6] [raid10]
md0 : active raid1 sda1[0]
      24418688 blocks [2\/1] [U_]
 
md1 : active raid1 sda2[0]
      24418688 blocks [2\/1] [U_]
 
unused devices: <none><\/code><\/pre>\n\n\n\n
Then power down the system:<\/p>\n\n\n\n
shutdown -h now<\/code><\/pre>\n\n\n\n
and replace the old \/dev\/sdb<\/em> hard drive with a new one (it must have at least the same size as the old one – if it’s only a few MB smaller than the old one then rebuilding the arrays will fail<\/strong>).<\/p>\n\n\n\n
Step 3: Adding The New Hard Disk<\/h3>\n\n\n\n
After you have changed the hard disk \/dev\/sdb<\/em>, boot the system.<\/p>\n\n\n\n
The first thing we must do now is to create the exact same partitioning as on \/dev\/sda<\/em>. We can do this with one simple command:<\/p>\n\n\n\n
sfdisk -d \/dev\/sda | sfdisk \/dev\/sdb<\/code><\/pre>\n\n\n\n
You can run<\/p>\n\n\n\n
fdisk -l<\/code><\/pre>\n\n\n\n
to check if both hard drives have the same partitioning now.<\/p>\n\n\n\n
Next we add \/dev\/sdb1<\/em> to \/dev\/md0<\/em> and \/dev\/sdb2<\/em> to \/dev\/md1<\/em>:<\/p>\n\n\n\n
mdadm --manage \/dev\/md0 --add \/dev\/sdb1<\/code><\/pre>\n\n\n\n
server1:~# mdadm --manage \/dev\/md0 --add \/dev\/sdb1
mdadm: re-added \/dev\/sdb1<\/code><\/pre>\n\n\n\n
mdadm --manage \/dev\/md1 --add \/dev\/sdb2<\/code><\/pre>\n\n\n\n
server1:~# mdadm --manage \/dev\/md1 --add \/dev\/sdb2
mdadm: re-added \/dev\/sdb2<\/code><\/pre>\n\n\n\n
Now both arays (\/dev\/md0<\/em> and \/dev\/md1<\/em>) will be synchronized. Run<\/p>\n\n\n\n
cat \/proc\/mdstat<\/code><\/pre>\n\n\n\n
to see when it’s finished.<\/p>\n\n\n\n
During the synchronization the output will look like this:<\/p>\n\n\n\n
server1:~# cat \/proc\/mdstat
Personalities : [linear] [multipath] [raid0] [raid1] [raid5] [raid4] [raid6] [raid10]
md0 : active raid1 sda1[0] sdb1[1]
      24418688 blocks [2\/1] [U_]
      [=>...................]  recovery =  9.9% (2423168\/24418688) finish=2.8min speed=127535K\/sec
 
md1 : active raid1 sda2[0] sdb2[1]
      24418688 blocks [2\/1] [U_]
      [=>...................]  recovery =  6.4% (1572096\/24418688) finish=1.9min speed=196512K\/sec
 
unused devices: <none><\/code><\/pre>\n\n\n\n
When the synchronization is finished, the output will look like this:<\/p>\n\n\n\n
server1:~# cat \/proc\/mdstat
Personalities : [linear] [multipath] [raid0] [raid1] [raid5] [raid4] [raid6] [raid10]
md0 : active raid1 sda1[0] sdb1[1]
      24418688 blocks [2\/2] [UU]
 
md1 : active raid1 sda2[0] sdb2[1]
      24418688 blocks [2\/2] [UU]
 
unused devices: <none><\/code><\/pre>\n\n\n\n
That’s it, you have successfully replaced \/dev\/sdb<\/em>!<\/p>\n\n\n\n
*Source: Howtoforge<\/a><\/p>\n","protected":false},"excerpt":{"rendered":"
This guide demonstrates how to remove a failed hard drive from a Linux RAID1 array (software RAID) and add a new hard disk to the RAID1 array without losing data. Note: A newer version of this tutorial is available that uses gdisk instead of sfdisk to support GPT partitions. Initial Note: In this example I […]<\/p>\n","protected":false},"author":1,"featured_media":3053,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"_seopress_robots_primary_cat":"","_seopress_titles_title":"How to Replace a Failed Hard Drive in a Software RAID1 Array - BigBox","_seopress_titles_desc":"","_seopress_robots_index":"","_themeisle_gutenberg_block_has_review":false,"footnotes":""},"categories":[2],"tags":[36,69,74,71,73],"class_list":["post-3052","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-kb","tag-disk","tag-hard","tag-mdstat","tag-replace","tag-software"],"_links":{"self":[{"href":"https:\/\/bigboxhost.com\/blog\/wp-json\/wp\/v2\/posts\/3052","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/bigboxhost.com\/blog\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/bigboxhost.com\/blog\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/bigboxhost.com\/blog\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/bigboxhost.com\/blog\/wp-json\/wp\/v2\/comments?post=3052"}],"version-history":[{"count":4,"href":"https:\/\/bigboxhost.com\/blog\/wp-json\/wp\/v2\/posts\/3052\/revisions"}],"predecessor-version":[{"id":3057,"href":"https:\/\/bigboxhost.com\/blog\/wp-json\/wp\/v2\/posts\/3052\/revisions\/3057"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/bigboxhost.com\/blog\/wp-json\/wp\/v2\/media\/3053"}],"wp:attachment":[{"href":"https:\/\/bigboxhost.com\/blog\/wp-json\/wp\/v2\/media?parent=3052"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/bigboxhost.com\/blog\/wp-json\/wp\/v2\/categories?post=3052"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/bigboxhost.com\/blog\/wp-json\/wp\/v2\/tags?post=3052"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}