When you create a new secondary image for a sync mirror and do not select the initial sync, if the source LUN is not yet assigned to the host (the source LUN is empty), the mirror will be considered synced when you issue the second command. As soon as you issue IO to the LUN it will be mirrored.

Then when you assign the source LUN to a host, all IO to the source will be mirrored to the secondary image (which is why you MUST initially sync any mirror if the source is assigned to a host - otherwise you will miss the drive signature that that host writes to the LUN).

There are a number of "states" that the mirror can be in "Synchronized", "Consistent", etc. See the Mirrorview White paper for a complete list of the image states - this will be useful when you want to see what the state is (page 8).

White Paper - EMC MirrorView Knowledgebook - FLARE 30—A Detailed Review.pdf

glen

The new mirror is activated as soon as you issue the command to create the secondary image - the mirror will send data to the secondary image as soon as you send IO to the source LUN. You do not need to send IO to the source LUN to activate the mirror.

Initial sync is only necessary one time - when you have an existing LUN that is assigned to a host and contains data - when you create the secondary image, you MUST perform initial sync to get the existing data to the secondary image (which is blank). If you do not do an initial sync, then the existing data on the source LUN will not be copied (mirrored) to the blank secondary image LUN. But all new writes will be mirrorred.

You only need to create a mirror one time.

Are you sure you're not talking about Async mirrors?

glen

So, if I understand you correctly, the luns will only be mirrored after IO is being performed?

The idea was to create all the remote mirrors with the script and on regular basis perform the initial sync. But that isn't correct if I read your answer...

All source luns are assigned to a host, so IO will be performed.

Will the initial sync take place?

All the remote mirrors have a status like "Consistent".

Regards, Bart

Hi, I am very (absolutely) sure I am not talking about Asynchronous mirroring...

We turned off the initial sync to save bandwidth on our ISL.... The intention was to initiate the synchronisation on different times for the approximately 100 remote mirrors...

I will fracture the remote mirrors and remove the secondary images... After that, I will add them again with the initial sync activated...

I guess, I will have some secondary images by then...

Okay... I think I get it now...

Last question, when I add an used lun as a secondary image, all existing data on that lun will be erased?

You can only run initial sync when you first create the secondary image, if you don't, the data on the secondary image will not match the source until all sectors have been written to on the source (which will be mirrored to the secondary).

glen

Well, thanks for your replies.

You were very helpful.