Inside System Storage -- by Tony Pearson

Tony Pearson Tony Pearson is a Master Inventor and Senior IT Specialist for the IBM System Storage product line at the IBM Executive Briefing Center in Tucson Arizona, and featured contributor to IBM's developerWorks. In 2011, Tony celebrated his 25th year anniversary with IBM Storage on the same day as the IBM's Centennial. He is author of the Inside System Storage series of books. This blog is for the open exchange of ideas relating to storage and storage networking hardware, software and services. You can also follow him on Twitter @az990tony.
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1 localhost commented Trackback

Thanks. You've made my point much better than I did myself.<div>&nbsp;</div> And glad you like the photo - hauntingly similar, huh?<div>&nbsp;</div> PowerPath, by the way, isn't replaced by SVC. At least, not until the SVC can:<div>&nbsp;</div> * Load balance across multiple host HBAs, each ideally targeted at different paths to the target storage for maximum availability - and dynamically balancing the workload based on the actual real-time performance of each path<div>&nbsp;</div> * Transparently redirect I/O's should one path or HBA fail or become overloaded<div>&nbsp;</div> * encrypt/decrypt all the data for one or more LUNS - on the fly, and irrespective of which HBA port/path (separately licensed feature built into the latest version of PowerPath).<div>&nbsp;</div> (Maybe SVC already does all these things - if so, I'm sure BarryW will chime in soon to correct me).<div>&nbsp;</div> As to SRDF - moving from one proprietary CLI to another is indeed undesirable.<div>&nbsp;</div> But moving from SRDF to IBM's equivalents also requires sacrificing utility, recoverability and function. Who wants to get locked in to a solution that does less and doesn't scale as large?<div>&nbsp;</div> And for total transparency, I note that only the blade-server version of the "i" are supporting 512-byte FC interfaces. The workhorse models of the family still rely on 520/528 byte that going to change any time soon?

2 localhost commented Trackback

Thanks evrything ;)

3 localhost commented Trackback

As if by magic, a Barry appeared...<div>&nbsp;</div> So SDD does load balance, failover and all the usual things you would expect from a multi-path driver. It doesn't do encryption, as that would need the same specific hardware/software support in all the devices SDD supports. Must also place some overhead on the host CPU and storage systems. I believe encryption was only recently added to PP and costs even more.<div>&nbsp;</div> So quite often the entire SVC system, hardware, licenses etc can be deployed by customers for less than they were paying for their PP licenses, and the SVC license is a one off payment!

4 localhost commented Permalink

BarryW, you should know by now that there is no free lunch. Your claim about "one off payment" does not fly.

5 localhost commented Trackback

PowerPath's encryption option uses the host CPU to do the actual encryption, and doesn't depend upon the hardware in the storage (although it is tightly integrated so that local and remote replicas are accessible by hosts in a Dev or DR scenario).<div>&nbsp;</div> And I wasn't aware that with SDD I could have two HBAs in a host connected to two separate SVC nodes, each of which are connected to different front-end ports on the storage accessing the same LUN. I had thought that you could only balance through a single SVC node...interesting.<div>&nbsp;</div> Must be a bear to keep synchronised - is there a RedBook that explains the interaction between SDD and the SVC nodes to ensure that data isn't corrupted or lost in the event of a path or node failure?

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