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I'm looking to build a 80 TB file based storage system. Ideally, I'd like to do this with a large JBOD and one server with a lot of cores.

My question is: Will JBOD containers (like Intel's) allow parallelization of disk seeks? Imagine process 1 asks for sector X, while process 2 asks for sector Y. If these are totally independent storage systems, disk A (which has X) and disk B (which has Y) can seek at the same time. Will the drive controller in JBOD systems support that?

Note that I'm planning on using a JBOD container such as Intel's.

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JBOD used generally means exactly what it says on the tin - just a bunch of disks. There's no raid, no disk consolidation, nothing. You'll see a whole bunch of separate devices down your controller.

Intel's 'JBOD' unit needs a RAID adaptor if you want to do anything more clever. For example: http://download.intel.com/support/motherboards/server/jbod2000/sb/jbod2000_config_guide_106.pdf

Includes examples that:

  • Don't RAID
  • do 'easier' RAID ( 0, 1, 10 )
  • do 'harder' RAID ( 5, 6, 50, 60 )

The RAID controller will let you do more clever things - exactly how clever is directly related to how expensive it'll be.

So the short answer to your question: No. The point of JBOD is that it's the lowest common denominator for getting a 'bunch of disks'. However, you could install a RAID card, and implement a higher order RAID system, like RAID 10 or RAID 50 and get some degree of parallelism as suited t oyour workload.

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  • Got it. JBOD should give me parallelism, though, if the files are stored on separate disks. That is, it should be possible to read one file on disk A and one file on disk B. Assuming 100Mb/s disk read and 6Gb/s interface, you could read dozens of files at once, no?
    – SRobert James
    Dec 10, 2014 at 18:30
  • Multiple spindles gives you better throughput and iops, yes. This is largely why RAID0 exists. Bear in mind that both your disks and your controller will have a speed limit. 6Gb/sec is around 600MB/sec, you'll start to suffer contention and worse latency at about 60% of that.
    – Sobrique
    Dec 10, 2014 at 18:55
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A JBOD (Just a Bunch Of Disks) is just that. It has no controller aside from what is necessary to provide power and data lanes to the disks. In a case of a more sophisticated JBOD, you will see a backplane and, depending on the technology used, maybe an expander.

The controller needs to be placed on the host's side, it will be connected to the JBOD with one or more typically multi-laned data cables. It will see all disks in a JBOD as single entities and will be able to control them as such.

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  • wabbit, does that apply even when using a JBOD container such as Intel JBOD system? Doesn't that make all the disks look like one, with a single controller and cable?
    – SRobert James
    Dec 10, 2014 at 14:00
  • Not out the box. You can buy RAID controllers to go with it.
    – Sobrique
    Dec 10, 2014 at 15:17
  • @SRobertJames The Intel JBOD 2000 seems to contain at least one expander (the data sheet is listing a dual-ported backplane, usually such configurations are available with two expanders for redundancy purposes, although no definitive statement about this fact is made in the data sheet). It has no RAID by itself.
    – the-wabbit
    Dec 10, 2014 at 21:14

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