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What is VM density with VMware and how to improve it

CartoonCalvin100X100.JPG By Calvin Zito, @HPStorageGuy  vmw-vexpert.jpg

The other day, I introduced you to our new HP 3PAR Get Virtual Guarantee.  Today, I have a podcast with my fellow vExpert Eric Siebert.  If you've been reading my blog, you know that HP 3PAR is a modern architecture designed with virtualization and cloud in mind.  In the podcast, Eric helps us understand some of the storage challenges created by server virtualization and how HP 3PAR's architecture overcomes those challenges.  And this is the foundation of our Get Virtual Guarantee - doubling VM density.  Here's the podcast with Eric:


You can download this podcast by doing a right-click and "Save as" here. You can subscribe to my podcast on iTunes - go to the iTunes store and search for "Around the Storage Block" or you can open this link and click on the "View in iTunes" button under my picture.


More info on Get Virtual

I also have a blog post on the VMware Alliances blog - that post has a YouTube version of the podcast I did with Eric, so if you're a visual person head over there and take a look at the blog post.   


I have to also repeat what I said the other day - as with any program like this, there are terms and conditions.  You can check them out on the Get Virtual program website


If you're thinking about coming to HP Discover, here's how you can get a $300 discount.  Click on this link (or click on the graphic below) and use the promo code in the graphic.  There is a session at HP Discover that will talk more detail on the Get Thin and Get Virtual Guarantees, #TB2830 on Thursday June 7th at 10 AM.  Eric and I also have a session #TB2713 - Ask the Experts: Storage for VMware virtualization.  It's on Wednesday June 6 at 2:45PM.  Stop by and say hi and ask questions!




nate | ‎05-25-2012 07:18 PM

Pretty good but I think one thing could of been mentioned that would of set some better perspective on it.


The wide striping at the core is the chunklets, and in Marc Farley's speak "micro raid arrays". Something that 3PAR doesn't provide a way to measure. A few years ago I came up with a basic script that could do this -


As the url implies that particular array had more than 81,000 RAID arrays on it. Especially when dealing with parity-based RAID I really believe the ASIC is what makes running so many arrays possible. The only other systems that I know of that use sub disk RAID are Xiotech and XIV. XIV is limited to RAID 1 even fully loaded they have a mere 3:1 DISK:CPU ratio! (60 CPU cores for 180 disks). Xiotech is less granular than 3PAR of course and I'm sure is less granular than XIV - though I'm not sure how much less - but it's still very limited in the number of RAID arrays that it supports per system (since they do RAID based on disk platters, there's obviously a finite number of platters you can get in a system and their RAID can't span boxes).


I extrapolated the number of RAID 1 arrays in the 3PAR F400 SPC-1 results to be around 108,000 in another post a couple of years ago. That was RAID-1 with 384 disks, Imagine RAID 5 with 1280 disks on the T800?


The ratios changed a bit with the V-class and the increased chunklet size, but the numbers are still pretty staggering.


The flip side to the ASICs is they are limited in capacity, a complaint I've had on deck going back to my T400 I bought in 2008. They are built with 15k PRM disks in mind. So from an I/O perspective you should be able to load up a 2-node V400 system with say 1,400 x 2TB SATA spindles because that is what the ASICs can drive (assuming 80 IOPS per SATA spindle), such a configuration is impossible given the capacity limits of the ASICs themselves.


So it's a double edged sword, the efficiency, performance, etc is still heavily in favor of the ASIC even with the capacity limits I just wish the capacity limits weren't there.


The other thing the chunklets/wide striping gives you which is rarely talked about is the fast RAID rebuilds, something that is pretty essential to using large capacity SATA disks. Just stacking parity drive after parity drive is not a scalable solution, having all of the drives participating in recovering from a disk failure not only lowers latency during recovery but also slashes the time it takes to recover. Oh and don't forget there's no hot spares, no dedicated parity disks. Also don't forget that even if you run out of "spare" capacity the system can continue to suffer disk failures and it will automatically use unallocated space(assuming there is any) as temporary space until disks can be replaced.


As nearline disks continue to explode in size, the industry is going to have to come up with a better way of providing redundancy - 3PAR of course is already there. I'm not a storage expert so I don't know what the alternatives might be to micro raid for block based storage. Will people just ditch parity based RAID altogether and go to mirroring only? triple mirroring for more redundancy ? With some folks tossing about numbers like disks in the 10s of TBs, it's going to be quite an issue to solve going forward. I had another post a couple years ago about "do you really need RAID 6?"


From an architecutal standpoint 3PAR really is an amazing system, it's not perfect, it has some warts here and there, the licensing can be hard to swallow at times but there's no other disk subsystem I'd rather use. I just hope that HP can keep the good 3PAR people happy, because that really does make a difference in the quality of reps. My own HP VAR has told me time and time again how much of a pleasure it is to deal with the 3PAR folks vs the HP folks and he always asks the question when he meets them "are you from 3PAR or not". The 3PAR folks really know what they are doing and are passionate - the HP side - less so.



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25+ years experience around HP Storage. The go-to guy for news and views on all things storage..

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