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Re: [dm-devel] noob usage question



Yes, I think I do want to create partitions.  My expectation is to create a mapping based on one or more raw physical device (luns).  There are a number features I would like implement behind my mapping target driver.  My understanding is that I can treat the mapping (the target device) as if it were a raw disk and that I can format it as appropriate for whatever workload will use it.

For instance... I need to present a device (it would appear to the OS as a raw block device) composed of ranges of blocks from different devices - spinning media, ssd, PCIe flash, etc.  My target driver can guarantee a QOS (throughput, latency, combo) and it will service read requests across the range of physical media comprising the target.

This target device would appear to the OS as a block device.  The workload that uses the device might require a filesystem on it, so I need to mount a FS.

That's what I'm aiming for.  I ran into problems trying to format my target device so I created a linear mapping and it behaved the same way... could not put a partition on it or format it.

-john


On Fri, Aug 9, 2013 at 4:22 PM, Brassow Jonathan <jbrassow redhat com> wrote:

On Aug 9, 2013, at 4:01 PM, John Strange wrote:

> When I create a linear target, I can't create partitions or format the mapped drive.  I get an invalid parameter argument for an ioctl.  I'm obviously doing something stupid.  What do I need to do to create partitions, format, mount a dm-n?

You don't want to create partitions, do you?

Just create an mapping and use it.  If you need another, create another.  Need to remove one, just remove it.

Also, I'm assuming you want to use device-mapper.  If you want persistent devices (ones that stick around after a reboot), you may wish to use LVM.

 brassow



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