Should we use MirrorView with iSCSI just for replication ?

With a 9Mb link and iSCSI, it would be advisable to stick to asynchronous mirroring. The latency involved in synchronous mirroring would result in poor response times for the hosts on the Primary CLARiiON.

Bearing in mind the link between sites is IP based, iSCSI would be the most sensible and cost effective option for the remote links. As with all iSCSI links though, I recommend that the iSCSI connections should be on a private VLAN.

My supervisor just asks me how much traffic will be transferred via the link & how frequent.

We would like to use it with VMWare Site Recovery Manager. Does MirrorView make a copy of selected VMFS from Site A to Site B & keep replicating the difference at a period we can define ?
OR we have to use SANCopy to copy data across before we can use MirrowView ?

Thanks

MirrowView will make the initial full copy and then copy changed blocks over the link. So the answer to the question of how much traffic will be transferrred over the link is dependent on your applications and how frequently the data changes.

I would recommend that you review the Knowledgebook for Mirrorview on PowerLink"

http://powerlink.emc.com/km/live1/en_US/Offering_Technical/White_Paper/H2251_clariion_mirrorview_asynch_dr_wp_ldv.pdf

In addition, if you are already connected to your switches from each array using FC and the sites are connected together using TCPIP, you could just use FCIP between the sites, rather than creating new connections using iSCSI.

It's probably easier to connect the two arrays using iSCSI, but it might be slower.

Remember that each time you Write data to the source LUN, you need to change the data on the mirror LUN. Using Synchronous mirroring will mean that before an acknowledgment is returned to the host, that the mirrored Write to the mirror will need to be completed first.

If you use Asynchronous mirrors, you bundle up the Writes and send in a batch fashion, but each Write to the source is acknowledged immediately.

regards,

glen

Dear Glen,

Thank you for your advice. The reason for not considering FCIP is we find that the price for such device - Like Brocade 7500 is very expensive.

Moreover, from the document, it says that MirrorView only supports Physical RDM. It may be a problem for us as all RDM are in Virtual Mode (As we would like to create log file for backup via vRnager currently).

Regards

Message was edited by:
TonyJK

If you want to use a device only to convert FC to IP you can use some other vendors FCIP devices. Like Qlogic 6142, it's much cheaper than Brocade 7500. We use it for storage replication over TCP/IP connection.
There are also other devices that are used only to transfer fiber channel over TCP/IP and nothing more, look for such device if you don't want to use all the functionality Brocade 7500 could offer you.

Many thanks for your advice. We will look into the QLogic Product.

Regards

It depends on how much data you are writing to the primary LUN's. You are the one able to tell your supervisor. Simply monitor what your application is doing (on windows using perfmon).
1 Big advantate of MV/A is however that writes to the same block which hasn't been replicated to the other side yet, will only be transfered once when the data is replicated. So if you write to the same block 250 times in 30 seconds (30s is the default by the way), the block will only be replicated once, so saving you the previous 249 writes to that block !



MV cannot see what is on the LUN's, so the Clariion cannot see whether it is VMFS or not. MV/A uses snapview (which comes with MV/A), so the state of a LUN at a given point in time will be replicated to the other side and each time replication occurs only the differences will be replicated.



You don't need SC to make the initial full copy, MV does that for you. And indeed: MV/S over a small 9Mbps line will make you suffer from bad response times.

Any new developments ?

I have discussed with my supervisor.

He says that let us wait and see. This is because he wants to implement the SAN at remote site first before looking into replication.

As mentioned in another post, the vendor suggests us to use CX4-120C instead of CX3-10C. They give the same price for both model. We don't know whether they make a mistake and is in the middle of clarifying with them.

Fellows in the Forum has suggested if the price is the same, we should go for CX4-120C and there is no problem for replication between CX4 and CX3. On the other hand, they mention that EMC pushes to use Recover Point (Instead of MirrorView).

The reason for replication is because we would like to use VMWare Site Recovery Manager and we have to wait until it recommends Recover Point before we make the decision.

Thanks for your advice again.

Message was edited by:
TonyJK