Enabling discard rendered caching device unuseable

Enabling discard rendered caching device unuseable

[Clemens Eisserer]

Hi,

After using bcache for 9 months without any issues, I discovered the
"discard" flag for the caching device.
Running 4.13.5 I gave it a try, however after reboot the caching
device failed to register with:

At reboot bcache failed with:
prio_read() bad csum reading priorities
prio_read() bad magic reading priorities

The SSD used as caching device was a OCZ-OCTANE with the latest
firmware, which worked (and works) flawlessly for years and has no
SMART issues.

Best regards, Clemens

Re: Enabling discard rendered caching device unuseable

[Michael Lyle]

Clemens--

I'm sorry for this experience; I've added discard to my list of things
to review.

I suggest avoiding discard for bcache; since the cache device grows
until it is nearly full and is kept in that state, there is little
benefit from it.

Mike

On Mon, Nov 6, 2017 at 2:04 AM, Clemens Eisserer <linuxhippy@gmail.com> wrote:
> Hi,
>
> After using bcache for 9 months without any issues, I discovered the
> "discard" flag for the caching device.
> Running 4.13.5 I gave it a try, however after reboot the caching
> device failed to register with:
>
> At reboot bcache failed with:
> prio_read() bad csum reading priorities
> prio_read() bad magic reading priorities
>
> The SSD used as caching device was a OCZ-OCTANE with the latest
> firmware, which worked (and works) flawlessly for years and has no
> SMART issues.
>
> Best regards, Clemens
> --
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Re: Enabling discard rendered caching device unuseable

[Clemens Eisserer]

Hi Michael,

> I'm sorry for this experience; I've added discard to my list of things
> to review.
>
> I suggest avoiding discard for bcache; since the cache device grows
> until it is nearly full and is kept in that state, there is little
> benefit from it.

Good to know, thanks for the advice.

Best regards, Clemens