Re: [SPDK] BDEV & VBDEV

[Kumaraparameshwaran Rathnavel <krath at cloudsimple.com>]

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Thanks Daniel.  So in the virtual subsystem the example in the tree is malloc devices.  So instead of that I can create my own subsystem like malloc devices right. Is there support for virtual subsystem from end to end . Say that when I get a read command from kernel initiator the SPDK reads the data n then sends it back to the initiator 

Thanking you, 
Param

Sent from my iPhone

> On 21-Oct-2016, at 11:18 PM, Daniel Verkamp <daniel.verkamp(a)intel.com> wrote:
> 
>> On 10/21/2016 06:31 AM, Kumaraparameshwaran Rathnavel wrote:
>> Hi Guys,
>> 
>> What is the difference between BDEV and VBDEV ?
>> 
>> Thanking You,
>> Param
> 
> Hi Param,
> 
> Regular bdevs expose raw block devices (NVMe namespaces, kernel block devices via libaio, etc.). They typically interface with a hardware device that needs to be polled periodically to check for completions.
> 
> A vbdev is a "virtual blockdev" that consumes one or more bdevs and produces another set of bdevs.  A vbdev can process each I/O and decide what to do with it - for example, it could send each I/O to an underlying bdev, or split a single request into multiple I/Os to several different bdevs to implement features like RAID, or even encrypt writes and decrypt reads to add a disk encryption layer.
> 
> We don't have any vbdev examples in the tree currently, but we plan to add an example vbdev that will read partition tables from a disk and expose each partition as another bdev that can be exposed as an iSCSI LUN or NVMe over Fabrics namespace.
> 
> Thanks,
> -- Daniel
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