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2.5″ Enterprise Arrays

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I was asked the question today, when will Enterprise arrays support 2.5″ drives as standard? It’s a good question, as at first glance the savings should be obvious; smaller, lower power drives, more drives in an array and so on.

However things aren’t that simple. Doing the comparisons and working out some of the basic calculations such as Watts per GB or GB per cm3 then 2.5″ drives don’t offer that much of a saving (if at all). I’ve posted some sample comparisons here.

I’m not aware of any vendors who are planning to offer 2.5″ drives in Enterprise arrays. Looking at the mechanics of making the conversion, then there would be a few issues; first is the interconnect, SAS versus FCAL, however that should be an easy one to resolve. Second, there’s the physical layout of the drives and prividing maintenance access to each of them. That might prove more tricky, achieving a high density footprint and providing access to each drive individually.

If anyone is aware of anyone planning to use 2.5″ drives as standard, please let me know.

About Chris M Evans

Chris M Evans has worked in the technology industry since 1987, starting as a systems programmer on the IBM mainframe platform, while retaining an interest in storage. After working abroad, he co-founded an Internet-based music distribution company during the .com era, returning to consultancy in the new millennium. In 2009 Chris co-founded Langton Blue Ltd (www.langtonblue.com), a boutique consultancy firm focused on delivering business benefit through efficient technology deployments. Chris writes a popular blog at http://blog.architecting.it, attends many conferences and invitation-only events and can be found providing regular industry contributions through Twitter (@chrismevans) and other social media outlets.
  • Ewan

    I wonder how long it will be before noone makes 3.5″ disks of any kind, will there really be much point once SAS and 2.5″ disks become the standard on desktop PCs alongside laptops?

  • Stephen Foskett


    I made similar observations last year in Storage Mag, and again on my blog this summer… So here’s my follow up over there…


  • Chris M Evans


    Thanks for the comments; sounds to me that as I thought, no plans from the main vendors anytime soon to move to the 2.5″ form factor. I wonder whether, unless PC manufacturers change the design of PC towers, we’ll see 2.5″ in tower PCs either. I can see 2.5″ being useful for small footprint PCs though.

    Looks like 3.5″ isn’t going away any time soon.

  • BarryWhyte

    This will come. As SAS gets a foot-hold – doing some benchmarking of the 15K RPM variants I am actually quite amazed at what a low cost controller like the DS3400 can give you. Having been through the whole – how can we make FC-AL as reliable as SSA loops, and now the much nicer SAS tree structure, I think SAS stands a good chance of longer term replacing FC-AL as the intra-controller topology. When this happens and is adpoted by the industry, we will see many more 2.5″ drives. Especially as SSD’s take hold over the next 3-5 years.

  • Chris M Evans

    So Barry, what do you think, 12-18 months before IBM has a viable enterprise 2.5″ product?

  • BarryWhyte

    I don’t know of any concrete plans for 2.5″ in the short term. Personally, I’m pushing some SAS based ideas, which are no more than concepts at the moment. More than that I can’t really say.

  • Chris M Evans

    Barry, I think that sums up my understanding, most major vendors have nothing on the horizon at this stage. Thanks for the feedback.

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