Add some tips about LV caching

[mirror/dsa-wiki.git] / input / howto / lvm.creole

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+== Random LVM stuff ==
+
+=== LV caching ===
+
+We use LV caching at least on godard.d.o and smit.d.o. Here are the setup instructions:
+
+* Make sure that both the HDD and SSD are in the same volume group.
+
+* Make sure module loading is enabled
+
+* Run the following command to enable LV caching for the srv LV in the vg0 VG, assuming the SSD is /dev/sda3:
+
+{{{
+  lvcreate --type cache --cachemode writethrough -L 120G -n srv_cachepool vg0/srv /dev/sda3
+}}}
+
+* It is currently not possible to resize a LV with a LVM cache. The workaround is to disable LV caching, resize the LV and reenable it. LV caching can be disabled with the following command:
+
+{{{
+  lvconvert --uncache vg0/srv
+}}}