zfs zpool degraded drive missing

I have a degraded zpool called storage of 4 6TB Drives in 2 mirrors. One of the drives on the second mirror is unavailable. All cables seem to to be plugged in physically. Did my device id change?

zpool status -v storage

NAME                                          STATE     READ WRITE CKSUM
storage                                       DEGRADED     0     0     0
  mirror-0                                    ONLINE       0     0     0
    sdc                                       ONLINE       0     0     0
    sdd                                       ONLINE       0     0     0
  mirror-1                                    DEGRADED     0     0     0
    ata-WDC_WD60EFRX-68MYMN1_WD-WX91D65355TK  ONLINE       0     0     0
    15417011366624190108                      UNAVAIL      0     0     0  was /dev/disk/by-id/ata-WDC_WD60EFRX-68MYMN1_WD-WX91D6535J36-part1

ls -l /dev/disk/by-id

total 0
lrwxrwxrwx 1 root root  9 Feb 22 10:56 ata-Samsung_SSD_840_EVO_250GB_S1DBNEADA00610E -> ../../sdb
lrwxrwxrwx 1 root root 10 Feb 22 10:56 ata-Samsung_SSD_840_EVO_250GB_S1DBNEADA00610E-part1 -> ../../sdb1
lrwxrwxrwx 1 root root 10 Feb 22 10:56 ata-Samsung_SSD_840_EVO_250GB_S1DBNEADA00610E-part2 -> ../../sdb2
lrwxrwxrwx 1 root root 10 Feb 22 10:56 ata-Samsung_SSD_840_EVO_250GB_S1DBNEADA00610E-part3 -> ../../sdb3
lrwxrwxrwx 1 root root  9 Feb 22 10:56 ata-WDC_WD60EFRX-68MYMN1_WD-WX11DA40H4ZK -> ../../sdc
lrwxrwxrwx 1 root root 10 Feb 22 10:56 ata-WDC_WD60EFRX-68MYMN1_WD-WX11DA40H4ZK-part1 -> ../../sdc1
lrwxrwxrwx 1 root root 10 Feb 22 10:56 ata-WDC_WD60EFRX-68MYMN1_WD-WX11DA40H4ZK-part9 -> ../../sdc9
lrwxrwxrwx 1 root root  9 Feb 22 10:56 ata-WDC_WD60EFRX-68MYMN1_WD-WX51D6410414 -> ../../sdd
lrwxrwxrwx 1 root root 10 Feb 22 10:56 ata-WDC_WD60EFRX-68MYMN1_WD-WX51D6410414-part1 -> ../../sdd1
lrwxrwxrwx 1 root root 10 Feb 22 10:56 ata-WDC_WD60EFRX-68MYMN1_WD-WX51D6410414-part9 -> ../../sdd9
lrwxrwxrwx 1 root root  9 Feb 22 10:56 ata-WDC_WD60EFRX-68MYMN1_WD-WX91D65355TK -> ../../sda
lrwxrwxrwx 1 root root 10 Feb 22 10:56 ata-WDC_WD60EFRX-68MYMN1_WD-WX91D65355TK-part1 -> ../../sda1
lrwxrwxrwx 1 root root 10 Feb 22 10:56 ata-WDC_WD60EFRX-68MYMN1_WD-WX91D65355TK-part9 -> ../../sda9
lrwxrwxrwx 1 root root  9 Feb 22 10:56 wwn-0x50014ee20b713dd3 -> ../../sdd
lrwxrwxrwx 1 root root 10 Feb 22 10:56 wwn-0x50014ee20b713dd3-part1 -> ../../sdd1
lrwxrwxrwx 1 root root 10 Feb 22 10:56 wwn-0x50014ee20b713dd3-part9 -> ../../sdd9
lrwxrwxrwx 1 root root  9 Feb 22 10:56 wwn-0x50014ee20c912489 -> ../../sda
lrwxrwxrwx 1 root root 10 Feb 22 10:56 wwn-0x50014ee20c912489-part1 -> ../../sda1
lrwxrwxrwx 1 root root 10 Feb 22 10:56 wwn-0x50014ee20c912489-part9 -> ../../sda9
lrwxrwxrwx 1 root root  9 Feb 22 10:56 wwn-0x50014ee260a4bd75 -> ../../sdc
lrwxrwxrwx 1 root root 10 Feb 22 10:56 wwn-0x50014ee260a4bd75-part1 -> ../../sdc1
lrwxrwxrwx 1 root root 10 Feb 22 10:56 wwn-0x50014ee260a4bd75-part9 -> ../../sdc9
lrwxrwxrwx 1 root root  9 Feb 22 10:56 wwn-0x50025388500a0d02 -> ../../sdb
lrwxrwxrwx 1 root root 10 Feb 22 10:56 wwn-0x50025388500a0d02-part1 -> ../../sdb1
lrwxrwxrwx 1 root root 10 Feb 22 10:56 wwn-0x50025388500a0d02-part2 -> ../../sdb2
lrwxrwxrwx 1 root root 10 Feb 22 10:56 wwn-0x50025388500a0d02-part3 -> ../../sdb3

edit

fdisk -l

Disk /dev/sda: 6001.2 GB, 6001175126016 bytes
256 heads, 63 sectors/track, 726751 cylinders, total 11721045168 sectors
Units = sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 4096 bytes
I/O size (minimum/optimal): 4096 bytes / 4096 bytes
Disk identifier: 0x00000000

   Device Boot      Start         End      Blocks   Id  System
/dev/sda1               1  4294967295  2147483647+  ee  GPT
Partition 1 does not start on physical sector boundary.

WARNING: GPT (GUID Partition Table) detected on '/dev/sdb'! The util fdisk doesn't support GPT. Use GNU Parted.


Disk /dev/sdb: 250.1 GB, 250059350016 bytes
255 heads, 63 sectors/track, 30401 cylinders, total 488397168 sectors
Units = sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disk identifier: 0xcb1189ee

   Device Boot      Start         End      Blocks   Id  System
/dev/sdb1               1   488397167   244198583+  ee  GPT

WARNING: GPT (GUID Partition Table) detected on '/dev/sdc'! The util fdisk doesn't support GPT. Use GNU Parted.


Disk /dev/sdc: 6001.2 GB, 6001175126016 bytes
256 heads, 63 sectors/track, 726751 cylinders, total 11721045168 sectors
Units = sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 4096 bytes
I/O size (minimum/optimal): 4096 bytes / 4096 bytes
Disk identifier: 0x00000000

   Device Boot      Start         End      Blocks   Id  System
/dev/sdc1               1  4294967295  2147483647+  ee  GPT
Partition 1 does not start on physical sector boundary.

WARNING: GPT (GUID Partition Table) detected on '/dev/sdd'! The util fdisk doesn't support GPT. Use GNU Parted.


Disk /dev/sdd: 6001.2 GB, 6001175126016 bytes
256 heads, 63 sectors/track, 726751 cylinders, total 11721045168 sectors
Units = sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 4096 bytes
I/O size (minimum/optimal): 4096 bytes / 4096 bytes
Disk identifier: 0x00000000

   Device Boot      Start         End      Blocks   Id  System
/dev/sdd1               1  4294967295  2147483647+  ee  GPT
Partition 1 does not start on physical sector boundary.

edit2 Didn't realize one disk wasn't even showing up. Looks like 2nd drive in mirror-1 is completly dead. The out put from sudo lshw -class disk helped me see that.

 *-disk                  
       description: ATA Disk
       product: WDC WD60EFRX-68M
       vendor: Western Digital
       physical id: 0.0.0
       bus info: scsi@0:0.0.0
       logical name: /dev/sda
       version: 82.0
       serial: WD-WX91D65355TK
       size: 5589GiB (6001GB)
       capabilities: gpt-1.00 partitioned partitioned:gpt
       configuration: ansiversion=5 guid=e4026c6a-61c5-9a4a-adaf-ebcdf8bba68c sectorsize=4096
  *-disk
       description: ATA Disk
       product: Samsung SSD 840
       physical id: 0.0.0
       bus info: scsi@3:0.0.0
       logical name: /dev/sdb
       version: EXT0
       serial: S1DBNEADA00610E
       size: 232GiB (250GB)
       capabilities: gpt-1.00 partitioned partitioned:gpt
       configuration: ansiversion=5 guid=8d48ca17-2e53-4ee4-a040-e80362e68eca sectorsize=512
  *-disk
       description: ATA Disk
       product: WDC WD60EFRX-68M
       vendor: Western Digital
       physical id: 0.0.0
       bus info: scsi@4:0.0.0
       logical name: /dev/sdc
       version: 82.0
       serial: WD-WX11DA40H4ZK
       size: 5589GiB (6001GB)
       capabilities: gpt-1.00 partitioned partitioned:gpt
       configuration: ansiversion=5 guid=5811c203-99cd-5342-bb8f-c838f896b64e sectorsize=4096
  *-disk
       description: ATA Disk
       product: WDC WD60EFRX-68M
       vendor: Western Digital
       physical id: 0.0.0
       bus info: scsi@5:0.0.0
       logical name: /dev/sdd
       version: 82.0
       serial: WD-WX51D6410414
       size: 5589GiB (6001GB)
       capabilities: gpt-1.00 partitioned partitioned:gpt
       configuration: ansiversion=5 guid=c24e5950-cd95-f94b-826a-21a004221d32 sectorsize=4096

Well, the output clearly states that one of the drives is 250GB. Either it was replaced, or it was corrupted in a way when it started report it's space erroneously. Take smartmontools and examine it with smartctl, it will show all of the info about it.