document the dal-rescue-02 spare (team#41135)

howto/quintex.md

@@ -493,6 +493,14 @@ See also the [IBM documentation on common IPMI commands](https://www.ibm.com/doc
 
 TODO: disaster recovery plan for the Quintex PoP
 
+If one machine becomes unbootable or unreachable, first try the [out
+of band access](#out-of-band-access). If the machine that failed *is* the OOB jump host
+(currently `dal-rescue-01`), a replacement box need to be shipped. One
+currently (2023-05-16) sits in @anarcat's office (`dal-rescue-02`) and
+should be able to act as a spare, with minimal testing beforehand.
+
+If not, a new spare needs to be built, see [howto/apu](howto/apu).
+
 <!-- what to do if all goes to hell. e.g. restore from backups? -->
 <!-- rebuild from scratch? not necessarily those procedures (e.g. see -->
 <!-- "Installation" below but some pointers. -->