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Snapshots - refreshing data?
Hi all, I'm currently evaluating Dell SC series storage but I am having a hard time finding info on snapshots (except for just taking a snapshot and delete them). Currently I am used to the behavior in 3PAR/IBM based arrays. Lets say I have a database on a single LUN (just for the sake of simplicity). I make a snapshot of this volume and present the snapshot to another machine to use the snapshot for development purposes. Now - Lets say I want to refresh the data on the development database - on the 3PAR I can just run a refresh on the current snapshot and the array refreshes the data. The WWN of the LUN under the development database does not change (and it is never unmapped, just unmounted in the OS of the development machine). Is it possible to do something like this, and if not - does Dell supply a tool to make it easy to automate the snapshot refresh process or will I need to script this through a API or using PowerShell?
DELL-Sam L
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November 8th, 2018 07:00
Hello fonzie82,
Here is the link to the DSM (Dell Storage Manager) & if you look on page 126 it explains about snapshots & how they are used. https://topics-cdn.dell.com/pdf/storage-sc2000_administrator-guide_en-us.pdf
Please let us know if you have any other questions.
jkrajic
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November 15th, 2018 01:00
Mike B Storage
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September 5th, 2019 10:00
I too am looking to how to refresh snapshot with changing WWN, but I cannot find it in the guide that is mentioned.
From what I can tell from the guide you:
But I cannot find a snapshot refresh, only a snapshot expire, which would mean I would need to then recreate snapshot which presumably would create a new different WWN from the first snapshot.
Mike B Storage
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September 6th, 2019 09:00
I think I found out how to do this:
In the CLI a snapshot is called a replay (a new term I have not heard of) and so:
“replay create” creates a PITC snapshot and
“replay createview” creates a LUN you can map to a server
And it looks as though you can move this view to a different replay – so I guess this means you can effectively refresh this view (LUN) with a new replay (snapshot PITC).
jkrajic
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September 9th, 2019 02:00
You can use only "replay create". I'm using this:
replay create -deviceid ${ORIG_LUN_WWN} -expire ${SNAPSHOT_EXP} -name '${SNAPSHOT_NAME}' -view '${VIEW_NAME}' -move -nomovereplay -purge -server '${TARGET_SERVER}' -lun ${LUN}
Mike B Storage
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September 9th, 2019 06:00
Thanks - I will try this when I get access to test system
Arctae24
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January 7th, 2022 13:00
I know this is an older topic, but I am trying to do this process with the PowerShell snapin and I am not having luck finding a way to refresh the volume with a new snapshot. Has anyone had any experience doing that?
Mike B Storage
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February 4th, 2022 03:00
I have not used Powershell, but the most difficult thing is the procedure as in the GUI, there is no "refresh snapshot" option so I believe the same is true for the Powershell CLI. The procedure is discussed here - https://www.dell.com/community/Compellent/How-to-restore-revert-data-from-a-snapshot-on-SC4020/td-p/7634615 and I use my procedure a lot and, although convoluted, it works. On this discussion Dell says "snapshots weren't designed to restore data, but for data progression down the tiers in a Compellent system." which I guess explains why there is no easy way to refresh a snapshot. Also Dell say "I spent a fair amount of my day trying to locate a doc resource for you, but unfortunately, I've been advised that one doesn't exist.", so there is not much documentation on snapshots either.