question about jbod...

[Inspector Jihad]

how is the data split between teh two drives? does the computer also see it as one drive and fills one up before moving to the next? and are some file split between the two drives? thanks

 

[Nothinman]

jbod stands for just a bunch of disks, there's no RAID involved at all, each disk shows up seperately.

 

[Inspector Jihad]

Originally posted by: Nothinman
jbod stands for just a bunch of disks, there's no RAID involved at all, each disk shows up seperately.

naw dawg...jbod is the "opposite" of partitioning...it takes a bunch of physical drives and makes one logical drive.

 

[Nothinman]

Um no, it doesn't. Technically, all RAID is the opposite of partitioning, but JBOD is supposed to be one disk = one device. Although I wouldn't be surprised if some manufacturer has bastardized the term.

What you're talking about is concatenation or a linear array. And how that works depends on the implemenation, but usually once one drive is filled it moves onto the next, if you want striping of data you'll need to use one of the real RAID levels.

 

[Inspector Jihad]

i believe that concatenation is reffered to as jbod.

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anyway, so it will fill up one drive and move on to the next one right? Now what if for example that drive one has 100 megs left and I save a 200 meg file...will it store half of that file in disk one and the other half in disk two?

 

[Nothinman]

anyway, so it will fill up one drive and move on to the next one right?

It would depend on the implementation and how the array was built, but generally yes.

Now what if for example that drive one has 100 megs left and I save a 200 meg file...will it store half of that file in disk one and the other half in disk two?

Obviously, since the array is presented as one big volume the filesystem doesn't know where one disk ends and another begins.

 

[Inspector Jihad]

ok, i wanted to confirm because if a file is split b/w two drives and one fails, then it would be an inconvience. no matter, I think this is what i'm going to do as I have a number of small drives. thanks for your help

 

[Nothinman]

i wanted to confirm because if a file is split b/w two drives and one fails, then it would be an inconvience.

And it won't be an inconvenience if the file is all on one drive and that drive fails?

 

[Shippy]

I was under the impression that unless you had some type of mirroring that if you lost one drive you lost the whole array? So with JBOD if you lose one drive then only the data on that drive is lost?

 

[Nothinman]

I was under the impression that unless you had some type of mirroring that if you lost one drive you lost the whole array? So with JBOD if you lose one drive then only the data on that drive is lost?

Sort of. There's a lot of variables involved, but since the filesystem is just laid out straight across the disks you might be able to recover the files on each disk seperately. With NTFS you'd probably only have a real chance on the first one or two disks because of where the MFT is placed. But with a filesystem like ext3 or XFS that has perodic backup superblocks and allocation groups you'd have a better chance.

But in general, yes, you should treat spanned filesystems as just as risky as RAID0.