Tag Archives: VNX - Page 4

CX or VNX Mirrorview with Snapview active on the remote side

Posted by on January 21, 2014 No comments

If you have a primary LUN which is replicated using MirrorView/S and you decide to run SnapView snapshots on the remote side, consider that writes to the secondary LUN may have to wait for the COFW activity to complete before an acknowledgement is sent back to the primary array.

So if you’re performing tests on the remote site by using SnapView snapshots, you may want to consider suspending the MirrorView session(s) first in order to guarantee performance on the production site.

A good scenario would be to create clones from the temporary fractured mirrors and as soon as the clones are fully in sync, split the clone from its primary – being the MirrorView secondary – and start the resync in MirrorView.

MirrorView has to wait for SnapViewAfter the write from the primary array (1) a COFW (Copy On First Write) (2) must take place if the write (1) overwrites a block that hasn’t been written to yet in order to maintain the point in time of the snapshot. After the COFW (2) is complete the acknowledgement (ACK) (3) can be sent back to the primary array.

So even if the snapshot isn’t used by a host, there’s already an increased activity on the remote array.

If the snapshot is in use by a host that writes to the snapshot, an unchanged block on the secondary LUN need to be copied to the RLP (Reserved LUN Pool) first before the overwrite can take place. This will also slow down any ACKs that need to be sent back to the primary array.

Conclusion

Be very careful when starting SnapView sessions on a secondary LUN and even more careful when using the secondary LUNs since it can have a severe impact on the response times of the primary LUN.

How to set the “The array is alive” on a specific day and time on a VNX

Posted by on September 10, 2013 No comments

The need for weekly messages

EMC’s Symmetrix already knew this feature for a decade or so (or even longer), but since a few years EMC’s pushing customers to make every array to email home once a week so they can keep track of its pulse. And they’re not joking about its importance either, since once an array skips a beat, a severity 1 ticket is being created to get that fixed as soon as possible. EMC truly seems to care about the arrays they have running all over the world, so they’re indeed in good shape and being monitored actively.

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EMC Midrange Mega Launch: the new VNX

Posted by on September 4, 2013 6 comments

Midrange Mega Launch 2013: #Speed2Lead in real life!

Although the Clariion platform was a great platform a couple of years ago, the constant growth of customers’ environments and their need for more performance automatically means that storage vendors constantly need to improve their products as well. EMC VNX was able to serve customers just right for the last few years. With the introduction of flash storage in storage arrays performance issues seemed gone, but know that flash devices can easily outperform any rotating device (disk) by 20, 30, maybe even 50 times and depending on the I/O pattern, the back-end of an array could be a serious bottleneck since it wasn’t originally designed for performance demands like that and the old FLARE that ran on the CPUs wasn’t sufficient for the performance demand. So although FAST VP helps getting hot data to performance efficient devices and cold data to the slower and cheaper devices, it’s obvious that the array technology needed to be upgraded. And just like every 3 years or so, the necessity for new technology has come.

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EMC World 2013, the final countdown has started!

Posted by on April 11, 2013 No comments

The countdown has started

Just 3 weeks and a few days to go and it’s EMC World again! Time to meet my old and new friends and finally getting some rays. the one thing I’ve been missing the last few weeks it’s the sun and I guess most Europeans agree with me. Don’t know what it’s like in other parts of the world, but I certainly need more heat than what we’re having now.

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EMC VNX Replication

Posted by on October 16, 2012 No comments

I want to bring the discussion about “VNX data replication” to your attention. It’s on ECN and the URL is https://community.emc.com/thread/149825. If you want to ask about replication specifically, you can post your questions here or on ECN.

The author, Rupal Rajwar is USPEED certified and works for EMC eServices Customer Support division since 2010.