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Cache is King!

One thing that has gotten a lot of attention in the last 6 months is how much cache you can put into a solution.  Fusion IO has caught fire with its cache cards that you put into the host.  Texas Memory and Violin have solid state arrays that can help accelerate your SAN environment.  But those only mask the real problem.

Most of the time people are not saturating their 8GB FC link or even their 10GB CNA link to between their host system and their storage.  So network is usually not that big of a problem (if configured correctly of course).

The cache cards that are installed in the host systems do offload some of the reads and writes that normally go to the storage array but unless the cache is shared, then you can get into situations where you are keeping multiple copies of the same data in multiple systems.  This is effective for each host but not for the entire data center.

Then there is the all mighty “lets put faster disk in between the real disk and the hosts” solution that has been around since we started getting off Ultra Wide SCSI disk arrays.  This does again solve the issue of performance but becomes either an one off solution or involves time to get up and running and only benefits the data that lands on those disks.

At IBM, the XIV Storage System has been evolving since we purchased the technology a few years ago.  When I first learned of the system I thought the information was wrong, no way could a box that was just a bunch of servers with no raid out perform some of the tried and tested systems not only at IBM but in the storage market.  After doing the research and talking to customers that run XIV in their datacenter, I was starting to believe.  Was I drinking the Kool-Aid (no this is not a Netapp Blog) or was this a real shift in the storage technology?

Fast forward a couple of years and now IBM is deploying the third generation of XIV. One of the biggest factors way customers switch to XIV is how it lowers the amount of administration overhead.  This shows up when other vendors are trying to put so many features and functionality into their product but they are missing the fact that most people want it to be easier.  As their data footprint grows, they know the amount of time to keep up with were data lives or the time it takes to provision a lun will grow exponentially.

It was only after talking with a customer who previously not purchased IBM storage and hearing their story of how much work went into keeping up with the day to day running of the storage that I understood that the XIV was more than just a pretty face/GUI.
Today, IBM announced the addition of solid state drives to its XIV system.  But wait, doesn’t XIV only use near line SAS drives and touts the whole ‘no tiers’ strategy?  Correct. The XIV system is adding these SSD drives not for another tier but to increase the amount of cache available to the entire storage array (unless you thing cache is really tier 0, then ok whatever.).  This improves performance of the entire array three times the original XIV GEN3 SPC-2/E benchmark.  But wait, there’s more!

Because XIV spreads the load across all of the modules in the array, all of the data that is stored gets a bigger benefit than just adding cache to a host.  The XIV can now also exclude certain volumes from benefitting from the improved performance allowing you to maintain efficient use of the SSD technology.  The XIV executes an intelligent prefetch of data that is triggered when random reads are sensed.  For random operations, XIV SSD cache will prefetch pages to increase the cache hit ratio.  With XIV, SSD hotspots are monitored and managed by the storage system.  Data placement algorithms from IBM Research are designed to improve wear leveling and optimize performance.  XIV SSD Caching is the first commercial implementation of this IBM research project.  The future of storage is going to change were customers react to requirements, projects and deployments that are easier to manage on a larger scale.A storage system like XIV that drives the tangible benefits of easy to use with the intangibles (seeing your kids on the weekends instead of doing a data migration on a volume that is out of space and you can’t add space on the fly or even roll back to a snapshot cause if you turn them on the box will melt) shows how IBM is ahead of the game.  For more information about XIV and the 3x improvement go here


Categories: XIV Tags: , , ,
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  1. February 15, 2012 at 8:09 am

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