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ViliusK
Asked: 2011-03-27 05:41:19 +0800 CST

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

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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?

external-hdd

2 Answers

  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.

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  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.

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