Robert Hancock wrote:
Jeff V. Merkey wrote:
Max Waterman wrote:
One further question. I get these messages 'in' dmesg :
sda: asking for cache data failed
sda: assuming drive cache: write through
How can I force it to be 'write back'?
Forcing write back is a very bad idea unless you have a battery backed
up RAID controller.
This is not what these messages are referring to. Those write through
vs. write back messages are referring to detecting the drive write cache
mode, not setting it. Whether or not the write cache is enabled is used
to determine whether the sd driver uses SYNCHRONIZE CACHE commands to
flush the write cache on the device. If the drive says its write cache
is off or doesn't support determining the cache status, the kernel will
not issue SYNCHRONIZE CACHE commands. This may be a bad thing if the
device is really using write caching..
So, if I have my raid controller set to use write-back, it *is* caching
the writes, and so this *is* a bad thing, right?
If so, how to fix?
Max.
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