How to avoid "Assuming drive cache: write through" message during restart?

external-hdd disk restart cache

114,390

Solution 1

What does the message: `asking for cache data failed, assuming drive cache: write through` mean?

The Linux block layer makes some assumptions about when writes are actually committed to disk. LSI RAID controller logical drives pretend to be SCSI disks, but the firmware and driver doesn't report whether the controller is in "write-through" mode or "write-back" mode. Without this information, the block layer assumes "write-through". This is safe, because the controller has a battery-backed cache.

LSI's engineers know that their driver should handle this better so you don't see this message. But it's not an error, and it doesn't affect the system.

Solution 2

Stumbled onto a flint-axe type fix -- since this occurs before and after login, started looking for mechanisms that could do that, and thought it might be sent to stdio by dmesg.

Using sudo dmesg -n 1 turned off the messages. It may be possible to automate that in grub. But seems like treating the symptom, not the disease.

114,390

ViliusK

Updated on September 18, 2022

Comments

ViliusK over 1 year
Does anyone know how to avoid getting this message:
```
Assuming drive cache: write through
```
Which is showing up after performing sudo shutdown -r now.

I restarted remotely but the computer did not restart. And I can't restore my remote connection to it. I want to be sure that it won't happen again. When I physically approached the computer and turned on the display, I found 3 lines saying:
```
Assuming drive cache: write through
```
All those messages were because of my sdd disk. Later I checked and found that sdd is my external USB 1TB disk.

Any ideas on how to prevent such situations in future?
- Admin about 13 years
  
  I might be wrong, but I don't think this message was the cause of the problem.
- Admin about 13 years
  
  Well, you might be right... I made such assumption, because computer was frozen and only this message was seen on the screen... Sadly, I did not get any advice. Next time I will have to plan computer restart in advance so I'll be next to my server.
- Admin over 12 years
  
  sudo update-pciids && update-usbids might fix the Assuming drive cache: write through. It is a command to update PCI and USB id's.
- Admin over 11 years
  
  The message "Assuming drive cache: write through" is from sd_read_cache_type() in the kernel and occurs when revalidating the device. The kernel could not determine the drive caching characteristics so it defaulted to assuming it could support write through and so it emitted this message. For some devices, this may be an erroneous default, but possibly on the majority it is OK. It is classed as an error message as you may not want it to be using this default. The message is a KERN_ERR level kernel message, hence why it appears.
- Admin over 11 years
  
  Probably your system locked up during whatever it does next, after the step that printed the message about disk caches
- Admin over 8 years
  
  why is this closed? i have the same problem
Thomas Ward almost 13 years

I don't think that answers the OP's question of how to prevent those messages, @guimaluf