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EMCISA V2- Doubts while studying
Hello Folks,
I am currently preparing for the EMCISA V2 cert, and while studying from the ISM V2 book, have a few doubts.
1. Snapshots- I haven't clearly understood what exactly a snapshot does? and Is it an alternative to backup? What's Snap FS?
2. Point in time copies- How a mere small amount of copy can store huge information and restore the data
3. A lot of confusion on Mirrorview, Snapview, SRDF and its variants ...
The explanation is ther in the book but, I would need a practical approach from an expert on these topics.
I will have some more doubts that I will ask in a separate post to avoid confusion.
Thanks for the help.
Regards
Harshal
AnkitMehta
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August 18th, 2013 10:00
1. Snapview Snapshots: It is a type of replication where point in time replica is made for the Source Lun where in this method, it doesn't copy the whole data however it records the change. The Reserved LUN Pool holds all the original data from the Source LUN when the host writes to a chunk for the first time. This operation is called Copy On First Write (COFW). The Private area where COFW's are stored is called Reserved LUN Pool commonly knowns as RLP. Yes, EMC Snapview Products (Snapshot + Clones) can be include disk-based backup and recovery, decision support and data testing,data warehousing, data reporting, and data movement operations etc.
2. I think this is where you are more confused. Snapview Snapshot is not used for Data Recovery but commonly used for Quick Restore for a particular point time...say a time where admin knows there was no corruption etc. For this Operation Source LUN should be available and bound. If there is no source LUN on which Session was activated then Snapview Snapshot can not restore the data. This is what happens:
- Source LUN > Start a Session and Activate the Snapshot.
- Point Time Replicas are made for this LUNs depending on what Admin configured it...daily, weekly, monthly etc.
- Now say, thats an Application LUN and the data needs to be presented to R & D or a backup server quickly...All you do is mount the Snapshot to the backup server.
A secondary server then activates (maps) a snapshot to the SnapView session. The snapshot views the original Source LUN data chunks that have been modified since the user started the session from the Reserved LUN pool and the unmodified data chunks from the Source LUNs.
3. If there are so many doubts on Replication, trust me then you are doing it wrong! You need a coaching! You may opt for VILT, if you do not understand from it they have an option where you can interact with the instructor via email or also, if you can you can register for an Instructor Led Class!
Moreover, please move this discussion to https://community.emc.com/community/connect/emcpp/student for better visibility,
dynamox
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August 18th, 2013 11:00
i wanted to reiterate that snapshots are not backups, they reside on the same array as your source LUN.
harshgw2k3
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August 18th, 2013 22:00
That explanation cleared almost all my doubts on snapshot... thanks.
As u know the instructor led training is not be taken thru personal expenses!!.. ;)
Cheers
AnkitMehta
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August 19th, 2013 00:00
You're welcome.
Yes, I can understand that!
Cheers!