Creating a drive-bay map

When the time comes to replace a drive, it is very nice to know which drives is missing. I created this drive map to help me figure out which drive disappeared.

I created this drive-bay map using a combination of:

• zpool status
• sesutil map
• lsblk
• camcontrol
• /var/run/dmesg.boot

I have not included /var/run/dmesg.boot here.

If you click on this image, you’ll see a larger version which is easier to read.

I went through sesutil output and mapped each device to the drive bay, including the serial number and glabel. Eventually, I found that Element 17 (lines 72-74 below) had nothing listed. This differs from Element 18 which contained no drive. The system was powered off, mostly so I could easily pull drives without interfering with the systems.

This is drive bay #16 in the diagram above. This drive has serial number 57NGK1ZGF57D.

After recovering the zpool, I looked back at an older snapshot on this system. The serial number is not found in the dmesg.boot output:

[dan@knew:/.zfs/snapshot/autosnap_2019-11-25_00:00:00_daily/var/run] $ grep 57NGK1ZGF57D dmesg.boot 
[dan@knew:/.zfs/snapshot/autosnap_2019-11-25_00:00:00_daily/var/run] $ 

But is is found in the most recent version of that file:

$ grep 57NGK1ZGF57D /var/run/dmesg.boot 
da18: Serial Number 57NGK1ZGF57D

zpool status

The problem is shows on line 34. The issue was: which drive is that? The problem wasn’t that a drive disappeared in a running system. The issue was it didn’t show up on boot. da18 wasn’t the drive in question.

sesutil map -u /dev/ses0

Element 1 is described as slot 01 which is the first drive at the bottom left of the front of the chassis. This drive cage is physically labelled as 0.

Element 2 is directly above that.

It is similarly interesting that da0 is bottom left, da1, is to it’s right, then da2, etc. But that’s not strictly true. da8 is above da9.

lsblk

I used this information to grab the label for a given drive.

sudo camcontrol devlist

This is include only for completeness.