OSDOCS-4667: document known issue with spare-gb feature of LVMS in microshift

Signed-off-by: Doug Hellmann <[email protected]>

Author: dhellmann

modules/microshift-lvms-configuring.adoc

@@ -36,12 +36,17 @@ device-classes: <2>
 <2> `map[string]DeviceClass`. The `device-class` settings. 
 <3> String. The name of the `device-class`.
 <4> String. The group where the `device-class` creates the logical volumes. 
-<5> unit64. Storage capacity in GiB to be spared. Defaults to `10`. 
+<5> unit64. Storage capacity in GiB to be left unallocated in the volume group. Defaults to `10`. 
 <6> Boolean. Indicates that the `device-class` is used by default. Defaults to `false`. 
 <7> unit. The number of stripes in the logical volume.
 <8> String. The amount of data that is written to one device before moving to the next device. 
 <9> String. Extra arguments to pas `lvcreate`, for example, `[--type=raid1"`]. 
 +
+[WARNING]
+====
+There is a race condition that prevents LVMS from accurately tracking the allocated space and preserving the `spare-gb` for a device class when multiple PVCs are created simultaneously. Use separate volume groups and device classes to protect the storage of highly dynamic workloads from each other.
+====
++
 [NOTE]
 ====
 Striping can be configured by using the dedicated options (`stripe` and `stripe-size`) and `lvcreate-options`. Either option can be used, but they cannot be used together. Using `stripe` and `stripe-size` with `lvcreate-options` leads to duplicate arguments to `lvcreate`. You should never set `lvcreate-options: ["--stripes=n"]` and `stripe: n` at the same time. You can, however, use both, when `lvcreate-options` is not used for striping. For example: 
@@ -51,4 +56,4 @@ Striping can be configured by using the dedicated options (`stripe` and `stripe-
 stripe: 2
 lvcreate-options: ["--mirrors=1"]
 ----
-====
+====