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GCM Sanity Check on SRDF Migration between V2 and V3
Hello Experts,
Had a quick sanity check needed on setting up SRDF between V2 and V3 arrays. The source devices are all even cylinder (355150 for example). However when they have the targets created on the V3 for migration, they will be odd cylinder (172075 for example). I don't believe GCM will be set at all in this case since the source is not odd cylinders, but it leaves the targets as odd cylinders for the future, which I have never liked. Is the only restriction here with odd cylinders on the target with RecoverPoint? I have been trying to find any limitations leaving them as odd cylinders on the target, but can't find much so was curious if anyone ran into this before and maybe I just hadn't come across the right documents yet.
thanks!
KW160
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January 18th, 2017 11:00
Correct, GCM will not be necessary in this circumstance. I am not aware of any limitations regarding odd-cyl-sized VMAX3/AF volumes at this time.
Ayrton_Senna1
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January 18th, 2017 10:00
I am not an expert but i will try to answer it.
GCM will only be set on target devs ( V3 ) when the source ( mostly intended for V2 ) is odd number of cylinders to overcome the inability of V3 arrays to exactly match size of devs on V2.
I am assuming you are using cli to create target devices on V3, if you don't like odd cylinder devs on V3, you can create larger device to make it even cylinders, but this prevents you to do change replication direction from V3 to V2.
Since its a storage migration, i am assuming you wont need to failover, so you can proceed with larger V3 device.
If you create 172076 cyl on V3 and set GCM manually, it will still be half a cylinder larger than the 355150 cyl V2 device. As GCM only spoofs or reduces the size by only half cylinder. This still doesn't provide you failover, failback functionality.
I am not sure about recoverpoint restriction with odd cylinder devices.
echolaughmk
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January 18th, 2017 11:00
Awesome...thanks for the sanity check!