Common Issues With Attaching Huge Capacity Hard Disks To Your Raspberry Pi

October 26, 2020 - 3 minute read -
rpi linux

Introduction

There are many reasons to attach a huge hard disk to the Raspberry Pi, whether you want to setup a Media server for all of your movies and music or whether a torrent machine (or both). A Hard disk with a huge capacity makes a lot of sense in these cases. I recently bought a 4TB hard disk (nick named Brick) and wanted it to be attached to my RPI for downloads and also to stream those downloads across my home network. The following are some hoops I had to jump through to get it working compared to a smaller capacity HDD.

Concern 1: Power Requirements

As soon as I connected my hard disk, I started hearing clicking sounds every few seconds. I thought it might be faulty hardware, but it was actually the drive trying to start up but failing due to lack of power.

There are a few things that can be done in this case

  • Use an external power supply for the HDD. Usually big capacity HDDs come with the requirement of an external power supply. But my 4TB WD HDD (Brick) didn’t.
  • Unplug all other unnecessary appliances. The power is shared among the different USB ports. This did the trick for me. I previously had a 64GB and 1TB hard disk attached. removing them, helped my brick to startup.
  • Ensure that the power Adapter is a high quality one with a high amperage. The one I used provided 2A.

Concern 2: HDD Automounting

Normally to make an external HDD mount, you need to understand it’s UUID and add a line into the /etc/fstab file. This tells the system how and where to mount the HDD on bootup. But when I added the line to the fstab file and rebooted the system. It showed that the Brick was not mounted. I rechecked the fstab and it was correct. This is when I thought of dmesg. dmesg is a tool which outputs the kernel buffer. This is useful for diagnostic purposes. I simply ran dmesg and I received the following output

[    5.680612] sd 0:0:0:0: [sda] Spinning up disk...
[    5.681206] scsi 0:0:0:1: Enclosure         WD       SES Device       4008 PQ: 0 ANSI: 6
[    6.717053] ......ready
[   11.917626] sd 0:0:0:0: [sda] Very big device. Trying to use READ CAPACITY(16).
[   11.918011] sd 0:0:0:0: [sda] 7813969920 512-byte logical blocks: (4.00 TB/3.64 TiB)

Notice the time difference from when it starts up the disk and when it figures out the size of the HDD. seems like around 4-5 seconds. This made me suspicious that maybe the system does not mount it because, it takes too long with such a big drive. I looked for a solution and found this. The solution was to add the line rootdelay=5 to /boot/cmdline.txt. After adding that and rebooting. It worked! (This may not be the best way to do this)

Concern 3: HDD Speed and RPI Performance

As I was trying to download a large file. I noticed it was failing and my Rpi started to hang. The lag was so bad that simply typing ls in the /media/pi/brick folder seemed to brick my system.

I used htop to understand what was happening There was one process which seemed to consume a lot of cpu cycles. mkfuse.exfat This was the software used to mount and handle exfat file system. The brick was formatted as exfat. I realized this was unusable and decided to format it to ext4 using gparted.

This time it was a world of difference, the rpi no longer got hung and the downloads were working. But there is a downside to using ext4. It cannot be easily used with other OSs like Windows or Mac OS. I anyway planned to stream everything over the network, so this wasn’t a big deal. If interoperability is important, then the HDD can be formatted as NTFS. This would allow it to be used with Windows as well. This is much slower than ext4, but from what I have seen it generally performs better than exfat on my Rpi.

End Note

Using a 4TB hard disk on a Raspberry Pi, is considerably different than simply attaching a USB or 500GB hard disk. Some of these issues can be handled by getting a dedicated server instead of an Raspberry Pi. There also might be other issues as well, time will tell.