Rubbish Maplin USB SDHC RAID Enclosure

phoneguy

It does not really matter if Prowla is taking his info from Wiki, Cisco or the Oxford English. He is, technically, quite correct. Playground level insults really don't have a place here btw.

zappahey

prowla wrote: »

No, it is you who is wrong - JBOD is where it presents as a bunch of disks, hence the term; RAID is where it combines them to present a larger drive.

Search for the topic in google - you'll find the answer (eg. this wiki link).

The packet the thing came in says JBOD.

The thing is, despite whatever wikipedia might say, JBOD is not a standard term and can mean whatever the manufacturer says it means.

However, using Google to find products, just about every array manufacturer seems to be referring to JBOD as a spanned array of disks.

You really need to look beyond wikipedia, it is far from definitive.

zappahey

phoneguy wrote: »

It does not really matter if Prowla is taking his info from Wiki, Cisco or the Oxford English. He is, technically, quite correct. Playground level insults really don't have a place here btw.

Can you point to the standard that defines what JBOD means?

Like this for RAID http://www.snia.org/sites/default/files/SNIA_DDF_Technical_Position_v2.0.pdf

phoneguy

If we get technical, JBOD would not apply to flash memory as it is not a 'dis(c|k)' as such. In the absence of any RFC's or standards it is going to come down to opinions.

Looking at it closely I'm going to have to discount the WIKI artical, as it contradicts itself in the final citation it gives - a link to PC Guide which says:

"Just A Bunch Of Disks" (JBOD)

If you have some disks in a system that you decide not to configure into a RAID array, what do you do with them? Traditionally, they are left to act as independent drive volumes within the system, and that's how many people in fact use two, three or more drives in a PC. In some applications, however, it is desirable to be able to use all these disks as if they were one single volume. The proper term for this is spanning; the pseudo-cutesy term for it, clearly chosen to contrast against "redundant array of inexpensive disks", is Just A Bunch Of Disks or JBOD. How frightfully clever.

With that in mind, the Wiki cannot be considered reliable and I yield that the only logical answer is JBOD, in the absence of any standards, cannot be anything specific, but can be anything a manufacture cares to say it is. In other words, they are free to make up anything they like, pretty much.

But as for the OP and his Maplin issue - just return it if you are not happy, they have pretty good customer service.

zappahey

phoneguy wrote: »

With that in mind, the Wiki cannot be considered reliable

At the risk of diverting the entire thread, Wikipedia should really carry a very large health warning that it is not a reliable source of reference. It can really be seen as no more than a starting point for research and every "fact" should be verified before use.

prowla

I chose to link to Wiki because it had a ready-printed definition of the term; if you'd like something better then here's one from a storage consultancy that spells it out.

In terms of JBOD & spanning/concatenation, typically the disks would be presented to the computer as individual disks (ie. JBOD), but the OS's disk manager (eg. Windows) could be configured to concatenate them into a spanned volume and present that to the application. Thus an application analyst might easily confuse the term by not understanding the role of the OS.

If you take a moment to think about the term "just a bunch of disks", if you have aggregated them info a concatenated LUN, then it is no longer just a bunch of disks, but instead has undergone some transformation to become a virtualised representation of them placed sequentially, and which requires some form of programmatic control to control above what just a disk does.

mttylad

For the OP to achieve individual drives for each SD card, why not by a USB SD card reader from Poundland per disc and a USB hub (also Poundland).

That should work.

prowla

mttylad wrote: »

For the OP to achieve individual drives for each SD card, why not by a USB SD card reader from Poundland per disc and a USB hub (also Poundland).

That should work.

Thanks for the thought.

I've decided to ditch the SD card approach (and will use the cards in a couple of cameras instead) and now have 4 USB sticks plugged into the ports in the back of the computer.

(FYI, my requirement was to play with host-based RAID and I didn't want to run 4 hard disks...)