rewrite ganeti instance install docs on gnt-chi

Those will provide a multi-disk setup.

howto/ganeti.md

@@ -164,36 +164,36 @@ the [storage servers documentation](howto/new-machine-cymru#storage-servers) for
 This assumes you are creating a 500GB VM, partitioned on the Linux
 host, *not* on the iSCSI volume. TODO: change those instructions to
 create one volume per partition, so that those can be resized more
-easily. The following is how `web-chi-03` was setup.
+easily. The following is how `tb-builder-03` was setup.
 
  1. create the disk on the SAN and assign it to the host group:
 
-        create virtualDisk physicalDiskCount=3 raidLevel=5 userLabel="web-chi-03" capacity=500GB;
-        set virtualDisk ["web-chi-03"] logicalUnitNumber=4 hostGroup="gnt-chi";
+        puppet agent --disable "creating a SAN disk"
+        $EDITOR /usr/local/sbin/tpo-create-san-disks
+        /usr/local/sbin/tpo-create-san-disks
+        puppet agent --enable
+
+    WARNING: the above script needs to be edited before it does the
+    right thing. It will show the LUN numbers in use below. This,
+    obviously, is not ideal, and should be replaced by a Ganeti
+    external storage provider.
 
     NOTE: the `logicalUnitNumber` here must be an increment from the
     previous highest LUN. See also the [disk creation instructions](howto/new-machine-cymru#creating-a-disk)
     for a discussion.
 
- 2. detect the new device on the Linux side:
-
-        iscsiadm -m node --rescan
-        ls -altr /dev/disk/by-path/*lun-4
-
-    TODO: is the `... --rescan` necessary?
-
- 3. find the associated WWID:
-
-        /lib/udev/scsi_id -g -u -d /dev/sdl
-
- 4. configure the disk on all Ganeti nodes, in Puppet's
+ 2. configure the disk on all Ganeti nodes, in Puppet's
     `profile::ganeti::chi` class:
 
         iscsi::multipath::alias { 'web-chi-03':
           wwid => '36782bcb00063c6a500000d67603f7abf',
         }
 
- 5. confirm that multipath works, it should look something like this":
+ 3. propagate the magic to all nodes in the cluster:
+ 
+        gnt-cluster command "puppet agent -t ; iscsiadm -m node --rescan ; multipath -r"
+
+ 4. confirm that multipath works, it should look something like this":
 
         root@chi-node-01:~# multipath -ll
         web-chi-03-srv (36782bcb00063c6a500000d67603f7abf) dm-20 DELL,MD32xxi
@@ -210,42 +210,31 @@ easily. The following is how `web-chi-03` was setup.
 
     and the device `/dev/mapper/web-chi-03` should exist.
 
- 5. partition the disk with `parted`:
-
-        parted --script --align optimal /dev/mapper/web-chi-03 \
-           mklabel gpt \
-           mkpart primary 0% 8MB \
-           set 1 bios_grub on \
-           mkpart primary 8MB 10008MB \
-           mkpart primary 10008MB 18008MB \
-           mkpart primary 18008MB 100%
-
-    TODO: this is one step that would be skipped if we have one iSCSI
-    volume per partition, obviously.
-
-    TODO: we probably do not need that `bios_grub` partition either.
-
  6. adopt the disks in Ganeti:
 
         gnt-instance add \
+              -n chi-node-04.torproject.org \
               -o debootstrap+buster \
-              -t drbd --no-wait-for-sync \
+              -t blockdev --no-wait-for-sync \
               --net 0:ip=pool,network=gnt-chi-01 \
               --no-ip-check \
               --no-name-check \
-              --disk 0:adopt=/dev/disk/by-id/dm-name-web-chi-03-part2 \
-              --disk 1:adopt=/dev/disk/by-id/dm-name-web-chi-03-part3,name=swap \
-              --disk 2:adopt=/dev/disk/by-id/dm-name-web-chi-03-part4
-              --backend-parameters memory=8g,vcpus=2 \
-              web-chi-03.torproject.org
+              --disk 0:adopt=/dev/disk/by-id/dm-name-tb-builder-03-root \
+              --disk 1:adopt=/dev/disk/by-id/dm-name-tb-builder-03-swap,name=swap \
+              --disk 2:adopt=/dev/disk/by-id/dm-name-tb-builder-03-srv \
+              --backend-parameters memory=16g,vcpus=8 \
+              tb-builder-03.torproject.org
+
+    NOTE: the actual node must be manually picked because the `hail`
+    allocator doesn't seem to know about block devices.
 
  7. at this point, the VM probably doesn't boot, because for some
     reason the `gnt-instance-debootstrap` doesn't fire when disks are
     adopted. so you need to reinstall the machine, which involves
     stopping it first:
 
-        gnt-instance shutdown --timeout=0 web-chi-03
-        gnt-instance reinstall
+        gnt-instance shutdown --timeout=0 tb-builder-03
+        gnt-instance reinstall tb-builder-03
 
 From here on, follow the [next steps](#next-steps) above.