Re: xfsdump INTERRUPT issue

[Stan Hoeppner <stan@hardwarefreak.com>]

On 12/7/2012 4:58 PM, Dave Chinner wrote:
> On Fri, Dec 07, 2012 at 03:04:57PM -0600, Stan Hoeppner wrote:
>> On 12/7/2012 4:16 AM, Dave Chinner wrote:
>>> On Thu, Dec 06, 2012 at 03:29:33AM -0600, Stan Hoeppner wrote:
>>>> On 12/5/2012 9:01 PM, Jeffrey Ellis wrote:
>>>> BTW, if your goal in all of this is simply copying all the directories
>>>> and files from one disk to another disk, you could have used "cp -a" and
>>>> been done already.  It takes longer to execute than xfsdump/xfsrestore,
>>>> but given you've been at this for many days now, "cp -a" would have
>>>> already completed--long ago.
>>>
>>> Unfortunately, using cp or rsync is not possible because the
>>> filesystem has a real-time device attached to it. It's basically a
>>> ~10GB data device and a ~500GB real-time device. I'd say it's from a
>>> DVR or something like that, and that Jeffrey is trying to put
>>> a bigger disk in the DVR....
>>
>> Ah, yes.  I didn't catch the RT volume.
>>
>> Incidentally, since the real-time feature has never been fully supported
>> under Linux, why are DVR manufacturers even using it?  Without GRIO and
>> the XBOW ASIC the real-time volume is pretty much useless isn't it?
> 
> The realtime volume actually has nothing to do with "real-time" at
> all. What it has is a deterministic allocator (bitmap rather than
> tree based) which is what you need for real-time applications (i.e.
> bound worst case performance). It got called the "real-time device"
> because of the applications it was used for, not because there is
> anything "real-time" about it.  IOWs, you don't need special
> hardware to take advantage of the properties of the allocator.
> 
> DVR manufacturers have decided to use it for 3 reasons:
> 
> 	1. Folklore says you need a RT device for
> 	   concurrent streaming workloads
> 	2. It's supported upstream

Define "support" and "upstream".  The few RT related posts over the past
years generated responses, some from you I think, that the RT code isn't
maintained, hasn't been for a long time.  Maybe I've misunderstood.

> 	3. It makes it hard for windows users to replace the
> 	   harddisk in the DVR by themselves (true).
> 
> #3 is the case we are seeing here.

Yes this seems to be the case.

> Cheers,
> 
> Dave.
> 

-- 
Stan

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