[gentoo-user] System only recognizes 1 of 2 partitions

[John Runyon <me@jfr.im>]

I recently received and installed a 3TB drive. Before formatting it, I
zeroed the first GiB (dd if=/dev/zero of=/dev/sdb bs=1M count=1024).
Then formatted with gdisk.

Both gdisk and parted report the partition table correctly as containing a
~1MB (empty) sdb1 and ~2.7TB sdb2 (with a protective MBR). However, on boot,
only one partition is recognized: the 1MB sdb1. And yet after running
partprobe, sdb2 will magically appear.

I've managed to work around this for now with a /etc/local.d/ file that
just does "partprobe; mount /home" but I'd like to figure out the underlying
cause... Has anyone ever run into this before?

# grep sdb /var/log/messages
Dec  9 01:38:49 precision kernel: [    1.224703] sd 1:0:0:0: [sdb] 5860533168 512-byte logical blocks: (3.00 TB/2.72 TiB)
Dec  9 01:38:49 precision kernel: [    1.228246] sd 1:0:0:0: [sdb] 4096-byte physical blocks
Dec  9 01:38:49 precision kernel: [    1.230017] sd 1:0:0:0: [sdb] Write Protect is off
Dec  9 01:38:49 precision kernel: [    1.231765] sd 1:0:0:0: [sdb] Write cache: enabled, read cache: enabled, doesn't support DPO or FUA
Dec  9 01:38:49 precision kernel: [    1.245054]  sdb: sdb1
Dec  9 01:38:49 precision kernel: [    1.247172] sd 1:0:0:0: [sdb] Attached SCSI disk
Dec  9 01:38:57 precision kernel: [   23.777108]  sdb: sdb1
Dec  9 01:38:58 precision kernel: [   25.120921] EXT4-fs (sdb2): mounted filesystem with ordered data mode. Opts: (null)

# gdisk -l /dev/sdb
GPT fdisk (gdisk) version 1.0.1

Partition table scan:
  MBR: protective
  BSD: not present
  APM: not present
  GPT: present

Found valid GPT with protective MBR; using GPT.
Disk /dev/sdb: 5860533168 sectors, 2.7 TiB
Logical sector size: 512 bytes
Disk identifier (GUID): 0A8A7DB1-45D0-44DD-AACB-1A4957077401
Partition table holds up to 128 entries
First usable sector is 34, last usable sector is 5860533134
Partitions will be aligned on 2048-sector boundaries
Total free space is 2014 sectors (1007.0 KiB)

Number  Start (sector)    End (sector)  Size       Code  Name
   1            2048            4095   1024.0 KiB  8300  Linux filesystem
   2            4096      5860533134   2.7 TiB     8300  Linux filesystem

# parted -l
[...]
Model: ATA ST3000DM001-1ER1 (scsi)
Disk /dev/sdb: 3001GB
Sector size (logical/physical): 512B/4096B
Partition Table: gpt
Disk Flags: 

Number  Start   End     Size    File system  Name              Flags
 1      1049kB  2097kB  1049kB               Linux filesystem
 2      2097kB  3001GB  3001GB  ext4         Linux filesystem
[...]