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* recommanded cache setting for rbd image
@ 2012-11-05 14:53 Stefan Priebe - Profihost AG
  2012-11-05 23:57 ` Josh Durgin
  0 siblings, 1 reply; 3+ messages in thread
From: Stefan Priebe - Profihost AG @ 2012-11-05 14:53 UTC (permalink / raw)
  To: ceph-devel

Hello list,

right now i'm testing rbd block devices with kvm using Default cache (no 
cache).

Is there any recommanded value for RBD? (i don't wanna loose data)

Stefan


^ permalink raw reply	[flat|nested] 3+ messages in thread
* Re: recommanded cache setting for rbd image
  2012-11-05 14:53 recommanded cache setting for rbd image Stefan Priebe - Profihost AG
@ 2012-11-05 23:57 ` Josh Durgin
  2012-11-06  7:34   ` Stefan Priebe - Profihost AG
  0 siblings, 1 reply; 3+ messages in thread
From: Josh Durgin @ 2012-11-05 23:57 UTC (permalink / raw)
  To: Stefan Priebe - Profihost AG; +Cc: ceph-devel

On 11/05/2012 06:53 AM, Stefan Priebe - Profihost AG wrote:
> Hello list,
>
> right now i'm testing rbd block devices with kvm using Default cache (no
> cache).
>
> Is there any recommanded value for RBD? (i don't wanna loose data)

It acts like a well-behaved disk cache (i.e. it respects
flushes/barriers from the guest), so it's no more likely to cause data
loss than a local hard disk in the event of an unexpected shutdown.

I recommend running it in writeback mode (the default when rbd cache = 
true). The best cache size will depend on your workload and hardware.


^ permalink raw reply	[flat|nested] 3+ messages in thread
* Re: recommanded cache setting for rbd image
  2012-11-05 23:57 ` Josh Durgin
@ 2012-11-06  7:34   ` Stefan Priebe - Profihost AG
  0 siblings, 0 replies; 3+ messages in thread
From: Stefan Priebe - Profihost AG @ 2012-11-06  7:34 UTC (permalink / raw)
  To: Josh Durgin; +Cc: ceph-devel

Am 06.11.2012 00:57, schrieb Josh Durgin:
> On 11/05/2012 06:53 AM, Stefan Priebe - Profihost AG wrote:
>> Hello list,
>>
>> right now i'm testing rbd block devices with kvm using Default cache (no
>> cache).
>>
>> Is there any recommanded value for RBD? (i don't wanna loose data)
>
> It acts like a well-behaved disk cache (i.e. it respects
> flushes/barriers from the guest), so it's no more likely to cause data
> loss than a local hard disk in the event of an unexpected shutdown.
>
> I recommend running it in writeback mode (the default when rbd cache =
> true). The best cache size will depend on your workload and hardware.

Thanks i'll check how this influence my disks and storage.

Thanks!

Stefan

^ permalink raw reply	[flat|nested] 3+ messages in thread
end of thread, other threads:[~2012-11-06  7:34 UTC | newest]

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2012-11-05 14:53 recommanded cache setting for rbd image Stefan Priebe - Profihost AG
2012-11-05 23:57 ` Josh Durgin
2012-11-06  7:34   ` Stefan Priebe - Profihost AG

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