Quick JBOD Question

2009-02-16 07:58:15

#1

kylef: Gone; +1,352|6757|N. Ireland

Google is throwing hundreds of different results at me, so I'm hoping some fellow tech team (and non-tech team too) members can help me out on this one. I've been throwing together a little server for a while now, but I want Windows to see all drives as one. I'm not going down the RAID0 route (failed me once, and the performance increase wasn't worth it) - so JBOD makes the most sense.

250GB SATA (Drive A)
300GB SATA (Drive B)

Windows will see this as a 550GB (well, probably a tad over 500GB) drive. If Drive A fails, is the data on Drive B safe? How is it recovered?

2009-02-16 08:02:55

#2

steelie34: pub hero!; +603|6645|the land of bourbon

well, technically making the volumes one disk (jbod) is pretty close to a raid0 set. the data is stored on the volumes sequentially instead of striped, and losing one means just that drive loses the data. if you're after fault tolerance, the most you can do is a raid1 (mirrored) set which gives you 250 gb of usable space.

Last edited by steelie34 (2009-02-16 08:07:55)

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2009-02-16 08:03:41

#3

GC_PaNzerFIN: Work and study @ Technical Uni; +528|6678|Finland

this: http://club.cdfreaks.com/f7/raid-jbod-question-203868/

"One advantage JBOD has over RAID 0 is in the case of drive failure. Whereas in RAID 0, failure of a single drive will usually result in the loss of all data in the array, in a JBOD array only the data on the affected drive is lost, and the data on surviving drives will remain readable. However, JBOD does not carry the performance benefits which are associated with RAID 0."

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2009-02-16 08:08:50

#4

kylef: Gone; +1,352|6757|N. Ireland

GC_PaNzerFIN wrote:
this: http://club.cdfreaks.com/f7/raid-jbod-question-203868/

"One advantage JBOD has over RAID 0 is in the case of drive failure. Whereas in RAID 0, failure of a single drive will usually result in the loss of all data in the array, in a JBOD array only the data on the affected drive is lost, and the data on surviving drives will remain readable. However, JBOD does not carry the performance benefits which are associated with RAID 0."

That's what I was looking for, thanks!

steelie34 wrote:
well, technically making the volumes one disk (jbod) is pretty close to a raid0 set. the data is stored on the volumes sequentially instead of striped, and losing one means all data is lost unless your controller can differentiate the volume divisions. (edit: 99% of controllers will nowadays) if you're after fault tolerance, the most you can do is a raid1 (mirrored) set which gives you 250 gb of usable space.

I thought the entire terminology of JBOD is that it isn't RAID at all - as the data in question will always remain one drive, and then another - not half and half. No?

2009-02-16 08:15:29

#5

steelie34: pub hero!; +603|6645|the land of bourbon

kylef wrote:
steelie34 wrote:
well, technically making the volumes one disk (jbod) is pretty close to a raid0 set. the data is stored on the volumes sequentially instead of striped, and losing one means all data is lost unless your controller can differentiate the volume divisions. (edit: 99% of controllers will nowadays) if you're after fault tolerance, the most you can do is a raid1 (mirrored) set which gives you 250 gb of usable space.
I thought the entire terminology of JBOD is that it isn't RAID at all - as the data in question will always remain one drive, and then another - not half and half. No?

right, it's not raid at all, i just meant similar to how multiple drives are used as one volume. the difference is how the data is stored. a crude example:

say you have a word file... in a stripe set (raid0), the file is split into two parts and each part written to the drives simultaneously, giving you better performance. this, however splits the file and will cause it to be lost should one drive fail.

same word file in a jbod, will be written to one disk only, until that drive fills up at which point the data will then be stored on the next disk. if a drive fails, only the data on that drive is lost, but you gain no performance increase.

2009-02-16 08:26:19

#6

kylef: Gone; +1,352|6757|N. Ireland

steelie34 wrote:
same word file in a jbod, will be written to one disk only, until that drive fills up at which point the data will then be stored on the next disk. if a drive fails, only the data on that drive is lost, but you gain no performance increase.

Yeah that's what I thought and want Thanks all, karma all round.

2009-02-16 10:57:01

#7

Bertster7: Confused Pothead; +1,101|6845|SE London

kylef wrote:
steelie34 wrote:
same word file in a jbod, will be written to one disk only, until that drive fills up at which point the data will then be stored on the next disk. if a drive fails, only the data on that drive is lost, but you gain no performance increase.
Yeah that's what I thought and want Thanks all, karma all round.

The data is rarely instantly accessible though. You have to fiddle about a bit (fix MBR and stuff). It is not uncommon for data to be lost on both drives in the event that one fails - but it is not certain, as is the case with RAID0 (which isn't really RAID either - no redundancy, so technically it doesn't qualify as RAID).

Last edited by Bertster7 (2009-02-16 10:57:31)

2009-02-16 12:20:35

#8

ElementalDragon: Member; +6|5834

yeah. not quite right to say that JBOD is even REMOTELY close to RAID 0. it's not any form of an array. it's just making two hard drives act as one.

2009-02-16 12:43:11

#9

steelie34: pub hero!; +603|6645|the land of bourbon

ElementalDragon wrote:
yeah. not quite right to say that JBOD is even REMOTELY close to RAID 0. it's not any form of an array. it's just making two hard drives act as one.

uh don't jbod and raid0 sets both make several disks appear as one?

Spoiler (highlight to read):
yes, so they are the same in that respect

2009-02-17 19:37:18

#10

ElementalDragon: Member; +6|5834

yes..... but as it's already been said, JBOD basically makes it one large continuous storage space, while Raid 0 is striped hard drives.... with the same data split between both drives, which is what results in somewhat of a performance increase depending on what you're doing.

JBOD with two or more drives and one drive fails = only lose data that was specifically on that drive

RAID 0 with two or more drives and one drive fails = pretty much certain loss of all data on every drive, because all data across the rest of the drives will be missing chunks that were stored on the drive that failed.

Two completely different storage methods, with two completely different benefits and side effects.

Last edited by ElementalDragon (2009-02-17 19:38:06)

2009-02-17 23:52:41

#11

FFLink: There is.; +1,380|6955|Devon, England

kylef wrote:
steelie34 wrote:
same word file in a jbod, will be written to one disk only, until that drive fills up at which point the data will then be stored on the next disk. if a drive fails, only the data on that drive is lost, but you gain no performance increase.
Yeah that's what I thought and want Thanks all, karma all round.

WOO!

Karma on Kyle! Let's party!

2009-02-18 04:33:47

#12

ElementalDragon: Member; +6|5834

0.o Karma for you when you just posted now? eerrrrr....... what?

Last edited by ElementalDragon (2009-02-18 04:34:08)

2009-02-18 05:01:53

#13

FFLink: There is.; +1,380|6955|Devon, England

ElementalDragon wrote:
0.o Karma for you when you just posted now? eerrrrr....... what?

Hey, he didn't describe the rules of this karma bonanza.

As it said, karma all round for all.

2009-02-18 05:49:50

#14

Scorpion0x17: can detect anyone's visible post count...; +691|7030|Cambridge (UK)

Where's my karma!?!?

2009-02-18 05:55:23

#15

GC_PaNzerFIN: Work and study @ Technical Uni; +528|6678|Finland

Scorpion0x17 wrote:
Where's my karma!?!?

I got yours too

Last edited by GC_PaNzerFIN (2009-02-18 05:56:02)

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2009-02-18 06:11:56

#16

ghettoperson: Member; +1,943|6913

I'd like some karma.

2009-02-18 13:57:04

#17

FFLink: There is.; +1,380|6955|Devon, England

TRIUMPH!

2009-02-20 07:55:18

#18

Bertster7: Confused Pothead; +1,101|6845|SE London

ElementalDragon wrote:
yeah. not quite right to say that JBOD is even REMOTELY close to RAID 0. it's not any form of an array. it's just making two hard drives act as one.

In all the Apple technical manuals they refer to JBOD as RAID0 concatenation and proper RAID0 as RAID0 striping.

So according to Apple they're both RAID0. But we all know what a bunch of fuckwits Apple are....

2009-02-20 12:57:42

#19

ElementalDragon: Member; +6|5834

yea.... can't trust a word Apple says. lol

BF2S Forums Quick JBOD Question

GC_PaNzerFIN wrote:

steelie34 wrote:

kylef wrote:

steelie34 wrote:

steelie34 wrote:

kylef wrote:

steelie34 wrote:

ElementalDragon wrote:

kylef wrote:

steelie34 wrote:

ElementalDragon wrote:

Scorpion0x17 wrote:

ElementalDragon wrote:

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