Single CSI driver supporting RWO, ROX, RWX volumes

[Sandeep P S]

Hi,

I have been rereading the CSI API spec and Kubernetes CSI design spec to see if the CSI spec has made any explicit assumption that a single CSI driver cannot support read write once(RWO), read only many(ROX) and read write many(RWX) volumes in a single driver. So, far, I have not come across anything that prevents a CSI driver to support all volume types. Can someone in this group confirm/deny this?

I also see that many cloud vendors have separate CSI drivers for RWO(block/disk volumes) and RWX (file shares). I'm wondering why they built it as separate drivers and not combine them into a single driver. Any clues? And I'm also wondering if this is somehow connected to CSI spec not supporting it. Any details on this is appreciated.

Thanks,

Sandeep

[Luis Pabon]

AFAIK, you are correct in that the CSI Spec does not prevent it. Also, our driver (Portworx) supports RWO and RWX on the same driver. That is all up to the storage system and is driver specific. I think GlusterFS also supports RWO and RWX, and maybe Ceph?

- Luis

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[John Griffith]

On Wed, Aug 7, 2019 at 7:42 PM Luis Pabon <lu...@portworx.com> wrote:

AFAIK, you are correct in that the CSI Spec does not prevent it. Also, our driver (Portworx) supports RWO and RWX on the same driver. That is all up to the storage system and is driver specific. I think GlusterFS also supports RWO and RWX, and maybe Ceph?

 

Agreed, and yes the Ceph plugin supports this as well, I believe there are others, or soon will be.

- Luis

On Wed, Aug 7, 2019 at 9:34 PM Sandeep P S <sandee...@gmail.com> wrote:

Hi,

I have been rereading the CSI API spec and Kubernetes CSI design spec to see if the CSI spec has made any explicit assumption that a single CSI driver cannot support read write once(RWO), read only many(ROX) and read write many(RWX) volumes in a single driver. So, far, I have not come across anything that prevents a CSI driver to support all volume types. Can someone in this group confirm/deny this?

I also see that many cloud vendors have separate CSI drivers for RWO(block/disk volumes) and RWX (file shares). I'm wondering why they built it as separate drivers and not combine them into a single driver. Any clues? And I'm also wondering if this is somehow connected to CSI spec not supporting it. Any details on this is appreciated.

Thanks,

Sandeep

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[Sandeep P S]

Thanks Luis, John. This confirms my analysis. 

On Wednesday, August 7, 2019 at 8:15:27 PM UTC-7, John Griffith wrote:

On Wed, Aug 7, 2019 at 7:42 PM Luis Pabon <lu...@portworx.com> wrote:

AFAIK, you are correct in that the CSI Spec does not prevent it. Also, our driver (Portworx) supports RWO and RWX on the same driver. That is all up to the storage system and is driver specific. I think GlusterFS also supports RWO and RWX, and maybe Ceph?

 

Agreed, and yes the Ceph plugin supports this as well, I believe there are others, or soon will be.

- Luis

On Wed, Aug 7, 2019 at 9:34 PM Sandeep P S <sande...@gmail.com> wrote:

Hi,

I have been rereading the CSI API spec and Kubernetes CSI design spec to see if the CSI spec has made any explicit assumption that a single CSI driver cannot support read write once(RWO), read only many(ROX) and read write many(RWX) volumes in a single driver. So, far, I have not come across anything that prevents a CSI driver to support all volume types. Can someone in this group confirm/deny this?

I also see that many cloud vendors have separate CSI drivers for RWO(block/disk volumes) and RWX (file shares). I'm wondering why they built it as separate drivers and not combine them into a single driver. Any clues? And I'm also wondering if this is somehow connected to CSI spec not supporting it. Any details on this is appreciated.

Thanks,

Sandeep

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