Re: [Gluster-devel] Fwd: Snapshot feature design review

[Fred van Zwieten]

Hi,

I have almost the same things as Paul mentioned. I also would like to see a snap retention feature. This could be build into the scheduling mechanism. Something like this:

gluster snapshot create < vol-name > [-n snap-name][-d description][-s <name>:<start-datetime>:<delta-datetime>:<keep> ...]

Where:

<name> is the name of this schedule

<start-datetime> is the timestamp for the first snapshot

<delta-datetime> is the specification for the time between snapshots

<keep> is the specification for the nr of snapshots for this schedule to keep

Multiple schedules should be possible.

Another thing, concerning the space management of snapshots. There should be an absolute max size limit on volume plus all of it's snap's. Look at NetApp's implementation for inspiration.

Cheers,

Fred

On Mon, Oct 28, 2013 at 4:26 AM, Paul Cuzner <address@hidden> wrote:

Hi,

I've just reviewed the doc, and would like to clarify a couple of things regarding the proposed design.


- I don't see a snapshot schedule type command to generate automated snapshots. What's the plan here? In a distributed environment the schedule for snapshots should be an attribute of the volume shouldn't it? If we designate a node in the cluster as 'master' and use cron to manage the snaps - what happens when this node is down/rebuilt or loses its config? To me there seems to be a requirement for a gluster scheduler - to manage snapshots, and potentially future tasks like post dedupe, data integrity checking or maybe even geo-rep intervals etc.

- snapshots are reliant upon dm-thinp, which means this version of lvm is a dependancy. Is there a clear path of migrating from classic lvm to dm-thinp based lv's - or is snapshots in 3.5 basically going to be a feature from this point forward i.e. no backwards compatibility.

- when managing volumes holding snaps, visibility of capacity usage attributed to snaps is key - but I don't see a means of discerning the space usage by snap in the CLI breakdown.

- on other systems, I've had hung backup tasks (for days!) holding on to snaps causing space usage to climb against the primary volume. In this scenario I was able to see snap usage and what client had the snapshot open to troubleshoot. In this scenario, how will the glusterfs snapshot present itself and be managed.

- How will the snapshot volume be perceived by Windows clients over SMB? Will these users be able to use the previous versions tab for example against the file properties in explorer?

- a volume snapshot is based on snaps of the component bricks. 3.4 changed the way that bricks are used on a vol create to require a dir on a filesystem not the filesystem itself. This change enables users to create multiple volumes from the same physical brick by placing different dirs on the bricks root - which is not necessarily a good idea. Given the 1:1 requirement of brick:volume, will this CLI behaviour be regressed to the way it was with 3.3.

Happy to talk further about any of the above, if needed.

Regards,

Paul Cuzner

----- Original Message -----
> From: "Nagaprasad Sathyanarayana" <address@hidden>
> To: address@hidden
> Sent: Friday, 18 October, 2013 5:22:31 AM
> Subject: [Gluster-devel] Fwd: Snapshot feature design review
>
> Gluster devel included.
>
> Thanks
> Naga
>
> Begin forwarded message:
>
>
>
>
> From: Nagaprasad Sathyanarayana < address@hidden >
> Date: 17 October 2013 9:45:05 pm IST
> To: Shishir Gowda < address@hidden >
> Cc: " address@hidden " < address@hidden >, " address@hidden " <
> address@hidden >, " address@hidden " < address@hidden >, "
> address@hidden " < address@hidden >, " address@hidden " <
> address@hidden >, " address@hidden " < address@hidden >, "
> address@hidden " < address@hidden >, " address@hidden " <
> address@hidden >, " address@hidden " < address@hidden >, "
> address@hidden " < address@hidden >, " address@hidden " <
> address@hidden >
> Subject: Re: Snapshot feature design review
>
>
>
>
> + Gluster devel.
>
> Hi all,
>
> Kindly review the design and provide any comments by next week. We are
> targeting to have the review comments incorporated in the design and post
> the final design by 28th of this month (October). If you need any discussion
> on the design, please let us know by 21st or 22nd this month.
> If anybody not copied must be involved in design review, please feel free to
> forward the design document to them.
>
> Thanks
> Naga
>
>
>
> On 16-Oct-2013, at 7:03 pm, Shishir Gowda < address@hidden > wrote:
>
>
>
>
>
> Hi All,
>
>
>
>
>
> The design document has been updated, and we have tried to address all the
> review comments and design issues to the best of our ability.
>
>
>
>
>
> Please review the design and the document when possible.
>
>
>
>
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> The design document can be found @
> https://forge.gluster.org/snapshot/pages/Home
>
>
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> Please feel free to critique/comment.
>
>
>
>
>
> With regards,
>
>
> Shishir
>

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