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November 1st, 2007 03:00
A simple question re SAN Copy ..
We are going to migrate from CX300 to CX3-20 Storage Array.
The consultant says that he will make use SAN Copy to copy data across. He mentions that he can copy across when we are still connecting Windows Servers to CX300.
We just want to know is it necessary for us to shutdown those servers when we copy data across (from CX300 to CX3-20). OR we shutdown those servers, start the copy process and during data migration, we can start up those Windows Servers ?
Thanks
The consultant says that he will make use SAN Copy to copy data across. He mentions that he can copy across when we are still connecting Windows Servers to CX300.
We just want to know is it necessary for us to shutdown those servers when we copy data across (from CX300 to CX3-20). OR we shutdown those servers, start the copy process and during data migration, we can start up those Windows Servers ?
Thanks
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dynamox
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November 1st, 2007 05:00
calle2
133 Posts
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November 1st, 2007 09:00
A couple of additional pointers... Initial Incremental SAN Copy is a full copy! The transfer block size is 2KB (post FLARE 19) so if you LUN is large it could take some time even though the benefit with ISC is that the source LUN can be online...
A better alternative would be to do a Full SAN Copy from the CLI using the "bulk" switch (better perforemane as the transfer block is larger). The bulk switch is only available from the CLI but allows your source LUN(s) to be online. Obviously the two LUNs will be inconsistent so an additional incremental copy needs to be done on top of that. During the final incremental your source needs to be quiesed.
I hope this helps
TonyJK2
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November 1st, 2007 16:00
I would like to clarify the following points
1) We are running FLARE 2.19, does it support the CLI bulk switch ?
2) How large a LUN we call it a large LUN ? At the present moment, the largest one we are using is 500GB. Do we consider it as large LUN ?
3) You have mentioned that the first SAN Copy is Full Copy. However, as the Servers connected to SAN are still running, the data is changing, does it mean that the Full Copy is somehow like a snapshot.
Your advice is sought.
calle2
133 Posts
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November 5th, 2007 10:00
To answer your questions:
Rel 19 does support the ¿bulk¿ switch. To reference the SAN Copy CLI guide:
¿-copywholelun -nomark command completes more quickly, but at the end of the session, the source and destination logical units are inconsistent. To make them consistent, you must run the session again¿.
In other words it doesn¿t mark the session or keep track of the changes/differences i.e. no COFW penalty which is together with the bigger transfer block size what makes it a faster option.
So to answer your second question, yes I think a 500 GB LUN to be copied as an ISC is rather larger and could take some time.
Hence the reason I am suggesting that for a one off migration you do a full copy either online (in two goes, first time as a bulk copy) and/or offline (remember with full copies and no ¿bulk¿ the source will have to be offline unless a snap or a clone is used as the source) instead of ISC.
I hope this helps
Calle