Should We Ever Talk About JBODs
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@scottalanmiller I'm sure I've seen "JBOD" option in some IBM raid controller.
Maybe it could be useful to idendtify disks as JBOD if they are used as part of an object based storage (like CEPH), to clarify that there is not any RAID in place.
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@Francesco-Provino said in Should We Ever Talk About JBODs:
Maybe it could be useful to idendtify disks as JBOD if they are used as part of an object based storage (like CEPH), to clarify that there is not any RAID in place.
Problem is, that's RAIN and not JBOD in CEPH. So specifically one of the things I'm trying to correct. JBOD would mean "not CEPH" explicitly.
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@Francesco-Provino said in Should We Ever Talk About JBODs:
@scottalanmiller I'm sure I've seen "JBOD" option in some IBM raid controller.
On a MegaRAID? If so, that's confusing. "Passthrough" would make way more sense. Especially since it doesn't know that it is talking to a physical single disk on one side and doesn't know how it is consumed on the other.
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The problem with JBOD is that essentially everything is JBOD at some point, and nothing is at another. In theory, you could have several "just disks" hooked via SATA or SAS to a machine and have them go all the way up with no connection to each other, but I've literally never seen this done in a server nor have I ever heard someone use JBOD to reference this one legitimate use of it.
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@scottalanmiller said in Should We Ever Talk About JBODs:
I'm not clear when we can ever usefully use the term where it doesn't prompt a long and confusing explanation to clear up what is actually intended. I have a feeling that this is a term that simply should not exist as there is just no time that using it is useful.
Does anyone have any idea of a time when it would actually be important to have this term and, if so, how would we use it without further explanation?
You configure Storage Spaces from JBODs. Or technically, DAS JBODs. JBOD enclosure?
I have a pile of JBODs... Literally a heap of hard drives waiting to find a trash can.
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The technical definition of JBOD are disks that haven't been RAIDed or anything yet.
So in that sense, you would use JBOD as in my SS example no matter the enclosure... not just with DAS. In anything.
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@Tim_G said in Should We Ever Talk About JBODs:
@scottalanmiller said in Should We Ever Talk About JBODs:
I'm not clear when we can ever usefully use the term where it doesn't prompt a long and confusing explanation to clear up what is actually intended. I have a feeling that this is a term that simply should not exist as there is just no time that using it is useful.
Does anyone have any idea of a time when it would actually be important to have this term and, if so, how would we use it without further explanation?
You configure Storage Spaces from JBODs. Or technically, DAS JBODs. JBOD enclosure?
I have a pile of JBODs... Literally a heap of hard drives waiting to find a trash can.
But once configured, they aren't JBODs
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@Tim_G said in Should We Ever Talk About JBODs:
The technical definition of JBOD are disks that haven't been RAIDed or anything yet.
Right... "yet". That's the problem. It's kind of an ephemeral state. For SS, we'd talk about "disks", no need to say JBOD, right? Does using the JBOD term add something to the terminology compared to just saying disks?
SS uses disks, just like RAID does. But when using RAID we never talk about the JBOD state because the RAID is enabled. SS is just RAID and/or RAIN. So JBOD wouldn't be more or less applicable there than in another circumstance. All systems are JBOD up to a certain point, and not after that point (unless we never do anything with the disks ever.)
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@scottalanmiller said in Should We Ever Talk About JBODs:
Does using the JBOD term add something to the terminology compared to just saying disks?
Disks doesn't tell you if they are Raided or not. JBOD specifically tells you they are not.
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@Tim_G said in Should We Ever Talk About JBODs:
@scottalanmiller said in Should We Ever Talk About JBODs:
Does using the JBOD term add something to the terminology compared to just saying disks?
Disks doesn't tell you if they are Raided or not. JBOD specifically tells you they are not.
What do you mean? If I have disks, they are disks, not arrays. JBOD doesn't tell me anything I don't know from the term "disks." Same as when working with RAID we don't have to specify JBOD for RAID to use, we just say disks. SS is just software RAID here, same as any other. No other RAID or RAIN system needs to use the term JBOD yet conveys all the same info.
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What conversation are you picturing where using the term disks or using the term JBOD would separate things? Every RAID array is JBOD under the hood. So any situation where saying disks would be confusing, so would JBOD.
In fact, the conversation that triggered this was someone using exactly these wrong terms - calling the banks of his RAID 10 disks JBODs when looking "under" the RAID level. And he's as much right as not, they are indeed JBOD at that level. But he could have just said "disks", too.
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I've always taken JBOD to mean disks concatenated together and presented as 1 disk to the OS
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@brianlittlejohn said in Should We Ever Talk About JBODs:
I've always taken JBOD to mean disks concatenated together and presented as 1 disk to the OS
So the opposite of the term
Instead of being separate disks, you feel that they are explicitly not separate?This highlights that not only do I feel that the term is redundant, it is also simply unknown. Everyone has a different definition, but all of them overlap with existing, explicit terms.
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If we go by Wikipedia...
https://en.wikipedia.org/wiki/Non-RAID_drive_architectures
JBOD is specifically a reference to non-RAID and non-span. So both the examples presented thus far (SS and concat/spans) are what JBOD, in theory according to wikipedia, should be telling us that we don't have. SS would be a RAID form, spanning is... well spanning.
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This is the wikipedia definition: "JBOD (derived from "just a bunch of disks"): described multiple hard disk drives operated as individual independent hard disk drives."
Basically, anything that ties the disk together (RAID, RAIN, Spans, etc.) would be the antithesis. All non-JBOD systems must, obviously, use JBOD under the hood, there is no way not to. But that's what we just call the disks.
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@scottalanmiller said in Should We Ever Talk About JBODs:
What conversation are you picturing where using the term disks or using the term JBOD would separate things? Every RAID array is JBOD under the hood. So any situation where saying disks would be confusing, so would JBOD.
In fact, the conversation that triggered this was someone using exactly these wrong terms - calling the banks of his RAID 10 disks JBODs when looking "under" the RAID level. And he's as much right as not, they are indeed JBOD at that level. But he could have just said "disks", too.
I meant it as that disks can be either raided or unraided. JBODs cannot be raided. If they were raided, it wouldn't be a JBOD anymore. However, a disk can still be a disk whether it's raided or not. See what I mean?
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@Tim_G said in Should We Ever Talk About JBODs:
@scottalanmiller said in Should We Ever Talk About JBODs:
What conversation are you picturing where using the term disks or using the term JBOD would separate things? Every RAID array is JBOD under the hood. So any situation where saying disks would be confusing, so would JBOD.
In fact, the conversation that triggered this was someone using exactly these wrong terms - calling the banks of his RAID 10 disks JBODs when looking "under" the RAID level. And he's as much right as not, they are indeed JBOD at that level. But he could have just said "disks", too.
I meant it as that disks can be either raided or unraided. JBODs cannot be raided. If they were raided, it wouldn't be a JBOD anymore. However, a disk can still be a disk whether it's raided or not. See what I mean?
Kind of. But when you look under a RAID array, it's a JBOD still... because under that level they are not yet RAIDed.
The SS world uses JBOD in that way.... it's JBOD even though RAID is on top.
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@Tim_G said in Should We Ever Talk About JBODs:
@scottalanmiller said in Should We Ever Talk About JBODs:
What conversation are you picturing where using the term disks or using the term JBOD would separate things? Every RAID array is JBOD under the hood. So any situation where saying disks would be confusing, so would JBOD.
In fact, the conversation that triggered this was someone using exactly these wrong terms - calling the banks of his RAID 10 disks JBODs when looking "under" the RAID level. And he's as much right as not, they are indeed JBOD at that level. But he could have just said "disks", too.
I meant it as that disks can be either raided or unraided. JBODs cannot be raided. If they were raided, it wouldn't be a JBOD anymore. However, a disk can still be a disk whether it's raided or not. See what I mean?
I still feel I need to clarify what I mean, as it can be taken differently than how I mean it.
If you have a RAID, it consists of disks. Those disks are still called disks whether they are in a raid or not. However, if you have a JBOD, you can be certain that there is no RAID involved because it's still at the JBOD stage. Once you apply RAID to a JBOD, it's no longer a JBOD then.
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@scottalanmiller said in Should We Ever Talk About JBODs:
@Tim_G said in Should We Ever Talk About JBODs:
@scottalanmiller said in Should We Ever Talk About JBODs:
What conversation are you picturing where using the term disks or using the term JBOD would separate things? Every RAID array is JBOD under the hood. So any situation where saying disks would be confusing, so would JBOD.
In fact, the conversation that triggered this was someone using exactly these wrong terms - calling the banks of his RAID 10 disks JBODs when looking "under" the RAID level. And he's as much right as not, they are indeed JBOD at that level. But he could have just said "disks", too.
I meant it as that disks can be either raided or unraided. JBODs cannot be raided. If they were raided, it wouldn't be a JBOD anymore. However, a disk can still be a disk whether it's raided or not. See what I mean?
Kind of. But when you look under a RAID array, it's a JBOD still... because under that level they are not yet RAIDed.
The SS world uses JBOD in that way.... it's JBOD even though RAID is on top.
Ah you replied before I could clarify, but you raised a good point.
Maybe JBOD is best described as what's presented to the OS? Maybe that's a direction we could take this?
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@Tim_G said in Should We Ever Talk About JBODs:
@Tim_G said in Should We Ever Talk About JBODs:
@scottalanmiller said in Should We Ever Talk About JBODs:
What conversation are you picturing where using the term disks or using the term JBOD would separate things? Every RAID array is JBOD under the hood. So any situation where saying disks would be confusing, so would JBOD.
In fact, the conversation that triggered this was someone using exactly these wrong terms - calling the banks of his RAID 10 disks JBODs when looking "under" the RAID level. And he's as much right as not, they are indeed JBOD at that level. But he could have just said "disks", too.
I meant it as that disks can be either raided or unraided. JBODs cannot be raided. If they were raided, it wouldn't be a JBOD anymore. However, a disk can still be a disk whether it's raided or not. See what I mean?
I still feel I need to clarify what I mean, as it can be taken differently than how I mean it.
If you have a RAID, it consists of disks. Those disks are still called disks whether they are in a raid or not. However, if you have a JBOD, you can be certain that there is no RAID involved because it's still at the JBOD stage. Once you apply RAID to a JBOD, it's no longer a JBOD then.
I understand what you mean. At least I think that I do. But let's break it down architecturally.
The storage team could provide tons of disks to the server team. To the storage teams it's always JBOD. But to the server team it might be RAID or a span. It's still JBOD, and still RAID. Depends where you are looking.
