SVC 4.3.0 Space Efficient (Thin Provisioing), Mirroring and much more


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So at last I can explain one of the reasons why we’ve all been so busy for the last six months with the somewhat landmark 4.3.0 release of our SVC software.

Its been a while since we released a new I/O function, in fact over 18 months since GlobalMirror was released, but this time we have three. Space-Efficient Virtual Disks (SEV) – the SVC implementation of what is commonly known in the industry as thin provisioning. Secondly, with the introduction of SEV, we now support Space-Efficient FlashCopy (SEFC). The third new I/O function is Virtual Disk Mirroring (VDM), now you can protect against an entire controller failure, not just individual drives, but the whole box.

As I’ve been waiting to break the details, functions, and industry leading performance we are bringing to the market I’ve had a chance to work on this post for a good few weeks (months) so it actually has a bit of structure to it!


Why is this a landmark release? Well we’ve had so many questions relating to if we could, or would, be doing SEV, our customers could see what this really means. What does it mean? Well, you can now have SEV on any storage controller. You don’t need to wait for other IBM products, HDS, HP, EMC, Sun, NetApp, NEC, Bull, Pillar etc to provide ‘thin provisioning’ – you can get it on all of them now with SVC. What could be seen as most important of all, its available at no additional charge. If you put SVC in your SAN to manage your storage you get SEV at no extra charge. Existing SVC customers with a current subscription and support can download the new release and also get these new functions at no extra charge (you must be licensed for FlashCOpy to use SEFC but there is no extra SEFC or SEV license).

Space-Efficient FlashCopy can dramatically reduce the amount of space needed because it uses disk space for only the changes between copies, not the entire copies themselves. SEFC is also a great fit for customers with many virtual machines, where multiple copies of boot drives may use significant storage. Since they are all much the same, cloning with SVC can dramatically reduce the storage needed. SEFC may also make it practical to take disk backups much more often, meaning that after an application failure you can get back online much more quickly and with less data loss.

Vdisk Mirroring provides that extra layer of protection for business critical application, and also has some interesting use-cases that may not be immediately apparent. Many of our Enterprise customers have been asking for this function, and since we have always said SVC lets you buy ‘low-cost RAID controllers’ now you can make them as robust as high-cost by mirroring the data between them. SVC itself is designed to deliver five 9s or better availability, which is one of the key attributes of an enterprise storage product. Our field support team studiously calculates and monitors our achievement of this objective. Since the SVC itself is highly-reliable, and you can now mirror between low-cost controllers, we are improving the general relability of your SAN and data by letting you buy two low-cost controllers, mirror the data between them and turn them into Enterprise level controllers for a fraction of the price. Nice. But the other benefits I’ll discuss later.

Lets go back a few months. I was amused that a post I made back in April hit the headlines and was on the front page of The Register for a week or so – I’m glad it was seen as an important step in the evolution of the SVC functionality, but really it was old news. (Thats not to say that a few people were surprised at my comments, however if you look back to my first post of the year you’d have know this was public domain). Nevermind the fact that I was simply quoting the SVC marketing manager who told the world this was coming back in December last year over at Byte and Switch.

Anyway, the SVC 4.3.0 code was actually announced last month (One or two astute readers found it!) but today is the day that we made our official press release statements as part of IBM’s Project Big Green. So now that the cat is finally out the bag, lets looks at the new features available when you upgrade to SVC 4.3.0 when it GA’s on June 27th.

4.3.0 Release Highlights

  • Space-Efficient Virtual Disks (SEV) – Use physical storage only when data is written and not when space is allocated. Dynamically allocate additional space on-demand as needed.
  • Space-Efficient FlashCopy (SEFC) – Make the target a Space-Efficient Virtual Disk and use capacity only for changes between the source and target. Its worth noting that you can use SEV anywhere in the ‘cascade’ of your FlashCopy. We place no restriction on where you use SEV, its quite a mouthful, but a Space-Efficient Multi-Target Incremental Cascaded FlashCopy is just as valid as using an SEV as the source or single target.
  • Virtual Disk Mirroring (VDM) – Specify two sets of storage to copy to, or add a second copy to an existing vdisk – local HA solution: protect against a failure of a disk system or an array within a disk system. Oh and again we have support the use of SEV VDM.
  • Support for 8192 Virtual Disks – Double the number of vdisks previously supported
  • 256 FlashCopy Targets – Since you are using a fraction of the space, you can now have 256 targets – and with SVC’s innovative implementation, in some configurations the impact of having 256 targets is no greater than having 1 target.
  • IPv6 support – Both SVC and the SSPC (master console)
  • Changes to the license terms – I will explain this in more detail in a subsequent post, but as mentioned above SEV is no additional charge over and above the base virtualization license. FlashCopy licensing does change to be ‘source’ capacity based. However, since a target may be the source for another FlashCopy care needs to be taken here.
  • Interop : Many things here, Brocade 8Gbit SANs fabric connectivity (SVC still runs at 4Gbit), Windows2008 Server GA support, Mac OS support, Pillar Data Controller support…

So there is much to talk about, and with my performance head on I want to go down into the nitty gritty detail of the SVC Space Efficient implementation. Unlike HDS who took the ‘lazy man’ approach and provided ‘semi-Thin-Provisioning’ by using their existing 42MB chunk size. (I am reliably informed some vendors refer to this as ‘chubby-provisioning’ 🙂 ) We’ve gone for fine-grained Space Efficiency, and allow you to modify the chunk, or grain size from 32K up to 256K in powers of 2. I personally believe we also have the fastest performing fine-grained SEV implementation on the market. (More details to follow)

This is just a taster for my next few posts, which are already written, but will be coming over the next few days, till then, fire away with questions, comments, thoughts and I’ll hopefully cover and if not will add to my posts.

I know everyone in IBM thats been involved with SVC 4.3.0, and those customers that we’ve already disclosed its contents to are very excited about this release. Hopefully you can all see the true value of a vendor-neutral in-band virtualization system, where we can implement the latest and greatest features. Thus allowing you to use these functions across your heterogeneous storage controllers, from the smallest RAID-only box to the largest Enterprise array.

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