* cache_mode none
@ 2012-10-04 10:24 Kingsly John
[not found] ` <20121004102406.GC17229-Z3X8UqLNtc1Swagx7F3lBaxOck334EZe@public.gmane.org>
0 siblings, 1 reply; 2+ messages in thread
From: Kingsly John @ 2012-10-04 10:24 UTC (permalink / raw)
To: linux-bcache-u79uwXL29TY76Z2rM5mHXA
Hi!
I've been trying out bcache over the last couple of weeks and couldn't find
this explained anywhere.
On my setup here while writing with cache_mode set to none, there's a
near constant 30-40kb/sec write happening to the flash device all through.
But in the other modes the amount of data written is significantly
higher.(While copying the same set of files into a freshly formatted bcache
device)
Does setting cache_mode to none just disable the cache for reading or does it
disable it for both reading and writing?
If it's only disabled for reads, then with cache_mode set to none would
bcache still recover from an unclean shutdown?
Kingsly
--
^ permalink raw reply [flat|nested] 2+ messages in thread
* Re: cache_mode none
[not found] ` <20121004102406.GC17229-Z3X8UqLNtc1Swagx7F3lBaxOck334EZe@public.gmane.org>
@ 2012-10-04 19:53 ` Kent Overstreet
0 siblings, 0 replies; 2+ messages in thread
From: Kent Overstreet @ 2012-10-04 19:53 UTC (permalink / raw)
To: linux-bcache-u79uwXL29TY76Z2rM5mHXA
On Thu, Oct 04, 2012 at 03:54:06PM +0530, Kingsly John wrote:
> Hi!
>
> I've been trying out bcache over the last couple of weeks and couldn't find
> this explained anywhere.
>
> On my setup here while writing with cache_mode set to none, there's a
> near constant 30-40kb/sec write happening to the flash device all through.
> But in the other modes the amount of data written is significantly
> higher.(While copying the same set of files into a freshly formatted bcache
> device)
>
> Does setting cache_mode to none just disable the cache for reading or does it
> disable it for both reading and writing?
>
> If it's only disabled for reads, then with cache_mode set to none would
> bcache still recover from an unclean shutdown?
In cache_mode none, nothing new will be added to the cache (neither from
writes nor cache misses), but the cache is still kept consistent -
that's the reason for the writing that still happens to the flash
devices, it's invalidating the cache whenever you do a write.
It will still read from the cache, because there might still be dirty
data in the cache.
^ permalink raw reply [flat|nested] 2+ messages in thread
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2012-10-04 10:24 cache_mode none Kingsly John
[not found] ` <20121004102406.GC17229-Z3X8UqLNtc1Swagx7F3lBaxOck334EZe@public.gmane.org>
2012-10-04 19:53 ` Kent Overstreet
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