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Re: [dm-devel] [lvm-devel] Default low water mark threshold for a new thin pool



thornber redhat com writes:

> On Tue, Feb 05, 2013 at 02:30:00PM +0530, M. Mohan Kumar wrote:
>> 
>> Hello,
>> 
>> We are adding a lvm2api for creating a thin pool. During thin pool
>> creation if user does not specify anything for the low water mark
>> thresold, it would result in 0 and no events will be generated when thin
>> pool capacity is reaching its full size.
>
> An event will be generated.
Yeah, I missed that. But if thin pool is consumed fully there is no
enough time to resize the pool and it may result in unwanted scenario?

>
>> I am not sure what should be the default low water threshold
>> percentage. Is there any recommended value for low water threshold value
>> in dm thin pools?
>
> It's very hard to say since it depends on your use case.  In general
> you want to allow dmeventd plenty of time to extend the pool before
> you run out of space.  So if you're seeing a _peak_ provisioning rate of
> 100meg a minute, I'd set the lwm to about 100meg.  It would be nice if LVM
> could help you through this process.

Do you mean mesaure how much MB/blocks dm-thin is able to provision in a
minute and treat it as the default lwm blocks?

>
> - Joe
>
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