Differences

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--- doc:appunti:linux:sa:raid_shrink [2025/01/03 18:20] – niccolo
+++ doc:appunti:linux:sa:raid_shrink [2025/01/07 10:45] (current) – niccolo
@@ Line 1: / Line 1: @@
 ====== Shrinking a RAID0 volume to add a smaller device to it ======
+**FIXME** Must add the **resize2fs** operation!
 Suppose we have:
@@ Line 7: / Line 9: @@
   * **/dev/sdb7** is the new component to be added to md0, **451GB** in size.
-=== Get the size of sdb7 ===
+=== Get the size of the new component sdb7 ===
 Get the exact size (in kb) of the **/dev/sdb7** partition. Using **parted** and display sizes in sector units:
@@ Line 23: / Line 25: @@
 so the size of /dev/sdb7 is 881070080 / 2 = **440535040** kb.
-=== Get the size of sda7 ===
+=== Get the size of the running component sda7 and RAID device md3 ===
 Get the size (in kb) of the **/dev/sda7** partition:
@@ Line 48: / Line 50: @@
 </code>
-The overhead of the RAID volume is 899608576 - 899476480 = **132096** kb. For safety we add an extra **128** kb for the RAID superblock.
+The overhead of the RAID volume is 899608576 - 899476480 = **132096** kb. For safety we allow an extra space of **128** kb for the RAID superblock.
+=== Calcluate the new array size ===
+So we can calculate the new array size:
+<code>
+new_array_size = new_component_size - raid_overhead - raid_superblock_size
+</code>
+<code>
+440535040 - 132096 - 128 = 440402816
+</code>
+It is now possibile to shrink the existing array **/dev/md3** to the new smaller size:
+<code>
+mdadm --grow /dev/md3 -z 440402816
+</code>
+Finally we can add the new component to the shrinked array:
+<code>
+mdadm /dev/md3 --add /dev/sdb7
+</code>