Ubuntu – simulate a slow hard drive

hard driveperformancetroubleshooting

I have hunch that a certain intermittent bug might only manifest itself when there is a slow disk read rate. Troubleshooting is difficult because I can't reliably reproduce it.

Short of simply gobbling IO with a high priority process, is there any way for me to simulate having a slow hard drive?

Best Answer

Use nbd, the Network Block Device, and then rate limit access to it using say trickle.

sudo apt-get install nbd-client nbd-server trickle

Related Solutions

Ubuntu – Is Disk Utility reliable

Yes, it is reliable. Run sudo badblocks -b 512 /dev/sda to scan the disk and find where the bad sector is. It will show the number of the bad sector. You can then verify it with:

sudo dd if=/dev/sda of=/dev/null iflag=direct bs=512 skip=sector_number count=1

Make sure you type the command exactly as stated, using the correct sector_number from badblocks. This should fail with an IO error ( since the sector is bad ). If it doesn't, then you got something wrong. If it does, then you can proceed with trying to repair the bad sector:

sudo dd if=/dev/zero of=/dev/sda oflag=direct bs=512 seek=sector_number count=1

After that, check the SMART status again and the pending_count should have gone down. If the reallocated_count is still zero, then the disk is fine.

Ubuntu – Why are all hard drives slow on the Ubuntu system

I switched from my current kernel, 32-bit PAE, to a 64-bit kernel. Disk writes are now fast. This was with Ubuntu 13.04.

Moral of the story: if you have more than 4GB RAM, use 64-bit Linux. Even though the PAE kernel may work, it may also have problems like this.

Best Answer

Related Solutions

Ubuntu – Is Disk Utility reliable

Ubuntu – Why are all hard drives slow on the Ubuntu system

Related Question