Monthly Archives: January 2014

Which Hot Spare will be used for a failed drive? – part 2

Hard Drive

A while ago I talked about Hot Spares and how they are picked when a rebuild is necessary. It was almost 2 years ago and you can read it here.

Since then the rebuild / equalize technology has changed! Well, not for existing systems, but the new VNX family aka VNX2 does things a bit differently.

In the old days when a drive failed, a suitable Hot spare would kick in and the unprotected LUNs (regarding the failed drive) would be rebuild onto the Hot Spare. After a while, when the rebuild was done and the failed drive was replaced by a replacement drive, the data on the Hot spare would need to be copied to that new drive. This was called equalizing.

In the VNX2 (with MCx) this last step doesn’t exist anymore. So that means the Hot spare that was used to contain the rebuilt data is not longer a Hot Spare! It has become a regular drive! And that replacement drive will now be a new Hot Spare. When configuring a new VNX2 you’d see rules about Hot Spares and you simply don’t even need to configure Hot Spares anymore. Just make sure you have some unconfigured drives and you’re good. Your VNX2 will make sure they’re used as Hot Spares from then on.

If I remember correctly the DMX4 had a similar feature back in 2008, but it now flowed to the midrange platform as well.

 

We did it! Open Line is now an EMC Signature Partner!

EMC Signature Partner

It’s not a technical post or a personal achievement post this time, but a warm congratulations to my employer, Open Line Consultancy. It took us 10 years, but leaving the EMC Velocity partnership we are now rewarded with the EMC Signature Partner status!

By posting this little post I’m saying congratulations to my employer, Jo Verstappen in particular and all my colleagues that made this happen over the last 10 years.

EMC Signature Partner

CX or VNX Mirrorview with Snapview active on the remote side

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.

EMC Elect 2014: here we are!

Elect 2014

It’s that time again: 2013 has past and a lot of vendors have nominations running on who their most loyal “servants” were in the past year. All large vendors do this and even Cisco joined the ranks with their Cisco Champions appreciation program. Microsoft has its MVP, VMware is known for the vExperts and since last year EMC has their Elect group.

EMC Elect 2014

Compared to 2013 the group has grown a little bit from 75 to 80 members and the list consists of some great minds that you might have met over the past 12 months. Some of them are hyper active on Twitter, some on ECN, EMC’s own Community Network (the forums) and some (or most) simply write what’s on their minds on their blog websites.

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EMC 2 or EMC II: which is which?

David Goulden is the new CEO of EMC Information Infrastructure (EMC II)

Joe Tucci remains Chairman and CEO of EMC Corporation. But what is the difference between the two EMCs? EMC2 or EMC II, which is which?

EMC Information Infrastructure, AKA EMC II is one of the businesses in the EMC Federation.

In their press release on January 8, 2014 EMC says: “Over the past year David has done a phenomenal job of running EMC’s Information Infrastructure business.  David is both knowledgeable and widely respected across EMC and fully deserves this promotion,” said Joe Tucci.  “I am looking forward to continuing to work with David in my current capacity as Chairman and CEO of EMC Corporation.”

EMC2 (Joe Tucci) is the major brand name and lies “on top” of the whole EMC family and the companies EMC II (David Goulden), VMware (Pat Gelsinger) and Pivotal (Paul Maritz) as such. IIG and RSA are part of EMC II.