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Not backing up will cost you!
superboyac:
I see. Yes, i'm probably misusing the term. I figured JBOD meant exactly what I thought, but it's not. What's the difference between what I'm describing and Raid-1?
4wd:
I see. Yes, i'm probably misusing the term. I figured JBOD meant exactly what I thought, but it's not.-superboyac (December 30, 2010, 06:34 PM)
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No, it might just be me. :) As I said, generally JBOD has implied what is really meant as SPAN when people talked about it. But JBOD really means what you have stated, Just a Bunch Of Drives - each individually addressable.
So your use is correct, however specifying JBOD still implies no data redundancy.
What's the difference between what I'm describing and Raid-1?
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With RAID-1, one HDD is mirrored to another - they both contain exactly the same data, ergo they, (AFAIK), have to be the same capacity. It's also taken care of by the controller, no user interaction, (apart from initial setup), required unless one HDD dies.
File syncing requires that the user run additional software, (and makes sure it's running), and action any errors, eg. files locked, permissions, etc, however the HDDs can be different capacities or the same HDD but different partition.
Incidentally, following on from worstje and JJ above, if you were going to try RAID-1, (even if only on a pair of your HDDs), I'd suggest using two different manufacturers, eg. WD 2TB and a Samsung 2TB, you'd be unlikely to end up with two HDD from the same batch. Also, it would probably be better to use Enterprise class HDDs instead of Desktop class.
40hz:
Generally, JBOD refers to combining separate HDDs into effectively one bigger HDD so that data is spanned across all of them. So if the 3rd HDD of a 5 HDD array dies, you've generally lost all data across all HDDs. You may be able to recover files using recovery software from the other HDDs but it'll be a long process.
By definition, JBOD is non-RAID and therefore there is no data redundancy.
-4wd (December 30, 2010, 05:33 PM)
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Actually, aren't there are two definitions for JBOD? One where data is spanned across the disks as you describe; and the other where a virtual disk manager is put on top of the "bunch of drives" but where each physical disk operates independently of the others?
If I recall correctly Goolge's G. Boudreau's Greyhole Project utilizes the second approach, but goes it one better by providing for data replication in software. Doing that makes Greyhole act much like a RAID-5 combined with an extremely flexible drive concatenation capability. This is similar to the 'Drive Extender' feature Microsoft just removed from their new Home Server release.
Last I heard it was still pre-1.0 release. But it is working and some people are using it.
Might be worth a look. (Sorry, don't have the link right this moment, but it's easy to find by - surprise! surprise! - googling 'Greyhole Project.') Link here.
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ADDENDUM: Whoops! 4wd got in there just ahead of me! ;D :Thmbsup:
EDIT: I stand corrected. Greyhole isn't Google's. It's the work of Guillaume Boudreau. Project website here. Personal blog here.
:-[
4wd:
Actually, aren't there are two definitions for JBOD? One where data is spanned across the disks as you describe; and the other where a virtual disk manager is put on top of the "bunch of drives" but where each physical disk operates independently of the others?-40hz (December 30, 2010, 07:03 PM)
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The spanned version is more properly called SPAN (DOH!) or BIG now, with JBOD correctly being just individually addressed drives. However, even some company descriptions seem to get it wrong.
eg. Some of Addonics products refer to JBOD (Concatenation), which I would have thought would really be SPAN or BIG, which they refer to on others. Some have JBOD (Individual) and BIG.
If I recall correctly Goolge's Greyhole Project utilizes the second approach, but goes it one better by providing for data replication in software. Doing that makes Greyhole act much like a RAID-5 combined with an extremely flexible drive concatenation capability. This is similar to the 'Drive Extender' feature Microsoft just removed from their new Home Server release.
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That looks very interesting, kind of like a combination of AFS, ZFS and RAID-5 :o
superboyac:
This is something I've been meaning to figure out, so I'm glad we're talking about it here. This stuff is confusing, complicated, and has lots of terms. So I'm going to try to simplify for myself.
In my situation, the storage is more so the goal rather than performance. I say that because I'd like to keep this as simple as possible. What I don't like about raid is the hardware requirements such as the disks having to be the same size. I mean, it makes sense that a backup drive is the same size, I just don't like it to be a requirement. I'd like to just cram in whatever drives I happen to find lying around. The synchronization and all that stuff will be taken care of with software, so once again, I'd like to avoid using hardware for things software can do. The only advantage I see in using hardware is performance. As long as I can copy files back and forth and streamp 1080p, that's all the performance I need.
Unless I am not understanding something, I'll be staying away from RAID. I'll be using a bunch of individual drives. I'll use Windows 7 library tools to create folders that span multiple drives. I'll use Super Flexible to sync my files back and forth (which I already use). I think that's a safe, solid setup, no?
I like these other spanning ideas mentioned above by 40 and 4wd, but unless I need additional features, I'm going to keep it real simple.
I do have a question, how do all these individual drives connect to the server? I can't imagine there's 16 SATA cables coming out the back plugging into the motherboard? Does it use a CAT5? Is something going on inside the box which combines it into one SATA or eSATA cable? How does this work?
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