Differences

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--- linux:centos:software-raid1-setup [2020/04/13 15:32] – odefta
+++ linux:centos:software-raid1-setup [2023/07/26 16:04] – [Re-add a good hard disk (after cable disconnection for example)] odefta
@@ Line 3: / Line 3: @@
 ====== Intro ======
-RAID 1 = mirrored pair of two hard disks
+RAID 1 = mirrored pair of two hard disks \\
-If one disk fail, the raid will continue to be operational.
+If one disk fail, the raid will continue to be operational. \\
-Read performance will be increased for parallel read operations.
+Read performance will be increased for parallel read operations. \\
-Write performance will be likely the same (almost the same).
+Write performance will be likely the same (almost the same). \\
 ====== Prerequisites ======
@@ Line 63: / Line 63: @@
 </code>
-==== Load automatically the raid 1 configuration at startup.  ====
+==== Load automatically the raid 1 configuration at startup  ====
 <code>
@@ Line 108: / Line 108: @@
 </code>
+==== Replace a failed hard disk in the raid configuration ====
+Suppose the /dev/sdb hard disk failed. \\
+To replace it with a good hdd, set it as failed and remove it from the array:
+<code>
+mdadm /dev/md0 --fail /dev/sdb --remove /dev/sdb
+</code>
+Add the new device to the array:
+<code>
+mdadm --add /dev/md0 /dev/sdb
+</code>
+==== Re-add a good hard disk (after cable disconnection for example) ====
+After reinserting the hard disk, it may be mounted now on a different device letter.\\Ckeck it by running:
+<code>
+fdisk -l
+</code>
+Output:
+<code>
+...
+Disk /dev/sdd: 4000.8 GB, 4000787029504 bytes, 7814037167 sectors
+Units = sectors of 1 * 512 = 512 bytes
+Sector size (logical/physical): 512 bytes / 4096 bytes
+I/O size (minimum/optimal): 4096 bytes / 4096 bytes
+</code>
+After identifying it, re-add it to the raid array with:
+<code>
+mdadm --manage /dev/md0 --add /dev/sdd
+</code>