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Forum Discussion
Hit 8Tb limit - how to expand to 18T physical?
Hi all, hoping for suggestions here for an easy(ish) fix... first let me stress that I've had experience in UNIX and I'm not stupid, but my training is out of date and to be honest I find all the technical hoop-jumping that seems to be necessary to run a ReadyNAS a little daunting.
Anyway, here's my situation. I have a ReadyNAS Ultra 6 Pro with the latest firmware, and I began a couple of years ago with a few 1Tb drives (4? can't remember) and have since expanded through 2Tb drives and now I have enough 3Tb drives to fill all six slots. Two of these are already hot-swapped in, but I think I'm hitting the 8Tb limit because the last volume expansion to 6x2Tb failed to expand the volume, and now it's failed again with the two new 3Tb drives.
My volume is, unfortunately, 94% full. I will try to get this down to a reasonable size, but it's not going to be easy. I don't have a backup at the moment, and I'm aware that I should have a strategy in place - but that's something I need to get around to later, as the lack of space is causing immediate issues that I need to solve quickly.
I realised that I needed a backup of the current data first of all, so what I have done already is use three of the four spare 3Tb drives to make a JBOD array on my Mac Pro, which I've mounted on the LAN, hoping to back up to that. So I have two tasks facing me here:
1. Is it a good idea to back up to the JBOD I've created (it's Mac OS Extended Journalled f/s at the moment)? If so, how do I do it in such a way that I can later reliably restore all my data including the permissions? I found a couple of other threads on here that talk about this kind of thing, but I found it all a bit hard to follow. Unless I've missed something, the official FAQ doesn't seem to help with this exact requirement, though it has plenty about backups. It mainly talks about rsync...
2. Once I've done that, I'm guessing I'll need to do a factory reset to get around the 8Tb limit. However, I'm now wondering whether I've done this wrong... do I need all six drives in place for that to work properly? I've used three of them to make the backup device, so if so, I've kind of shot myself in the foot :(
Any help very much appreciated, even if it's just a link to the best information source...
Thanks!
Anyway, here's my situation. I have a ReadyNAS Ultra 6 Pro with the latest firmware, and I began a couple of years ago with a few 1Tb drives (4? can't remember) and have since expanded through 2Tb drives and now I have enough 3Tb drives to fill all six slots. Two of these are already hot-swapped in, but I think I'm hitting the 8Tb limit because the last volume expansion to 6x2Tb failed to expand the volume, and now it's failed again with the two new 3Tb drives.
My volume is, unfortunately, 94% full. I will try to get this down to a reasonable size, but it's not going to be easy. I don't have a backup at the moment, and I'm aware that I should have a strategy in place - but that's something I need to get around to later, as the lack of space is causing immediate issues that I need to solve quickly.
I realised that I needed a backup of the current data first of all, so what I have done already is use three of the four spare 3Tb drives to make a JBOD array on my Mac Pro, which I've mounted on the LAN, hoping to back up to that. So I have two tasks facing me here:
1. Is it a good idea to back up to the JBOD I've created (it's Mac OS Extended Journalled f/s at the moment)? If so, how do I do it in such a way that I can later reliably restore all my data including the permissions? I found a couple of other threads on here that talk about this kind of thing, but I found it all a bit hard to follow. Unless I've missed something, the official FAQ doesn't seem to help with this exact requirement, though it has plenty about backups. It mainly talks about rsync...
2. Once I've done that, I'm guessing I'll need to do a factory reset to get around the 8Tb limit. However, I'm now wondering whether I've done this wrong... do I need all six drives in place for that to work properly? I've used three of them to make the backup device, so if so, I've kind of shot myself in the foot :(
Any help very much appreciated, even if it's just a link to the best information source...
Thanks!
19 Replies
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- Ok, now I'm puzzled... I DO have four disks per layer, don't I?
Physical drives:
3 3 3 3 2 2
Top layer:
1 1 1 1 - -
Bottom layer:
2 2 2 2 2 2
So I suppose that makes:
1+1+1+2+2+2+2+2 = 13Tb for single redundancy and
1+1+2+2+2+2 = 10Tb for dual redundancy.
I can't see where you got 7Tb :(
You know, all of this would be SO much easier if the RAIDar web control panel would actually give the details of the RAID structure in use. Is this shown anywhere? I've not found it yet... - Oops. I misread your post as 4x2TB and 2x3TB, I think.
Using single-redundancy your volume capacity rounded down to the nearest TB would be 11TB so you are using single-redundancy
If you were using X-RAID2 dual-redundancy it would be indicated in Frontview under Volumes. Since you are using single-redundancy it would just indicate that you are using X-RAID2. - Thanks mdgm! A couple of things I'm still not sure about here though:
1. Do I choose to use dual-redundancy myself, or will the system select it automatically when it sees fit?
2. What's wrong with my calculation above that shows 13Tb for single redundancy? I thought I understood how X-RAID2 worked... I can see how it would be 11Tb if there were no layers involved, only sets of disks - but this would effectively be two RAID 5 systems made of physical disks, wouldn't it? i.e. (4-1)x3Tb = 9, and (2-1)x2Tb = 2.
I thought X-RAID2 would use the disks horizontally in layers, so I'd get (4-1)x1Tb = 3 and (6-1)x2Tb = 10... - 1. You would need to backup your data and do a factory default (wipes all data, settings, everything). There would be a 10 minute countdown in which you can open RAIDar and click setup and choose the RAID mode. After that if you haven't confirmed a RAID mode choice it will be chosen for you. When you click setup in RAIDar during the 10 minute countdown there is a checkbox under X-RAID2 which you can tick to choose to use dual-redundancy.
2. 13TB is the amount before overheads. Also 13TB is measuring where 1TB = 1000^4 Bytes (how disk manufacturers measure capacity) whereas the NAS like most PCs considers 1TB = 1024^4 Bytes. So 13/1024^4*1000^4=11.82. Allowing for overheads and rounding down it easy to get the 11TB figure. - That answers everything I needed to know, completely. Thank you!
So I'm now anticipating that 6x3Tb will give me about 13 REAL Tb. I wish disk manufacturers would use proper measures and stop confusing everyone... :( - Personally I think the power-of-10 units (TB) are more natural.
My recollection is that power-of-2 (TiB) was a Microsoft hack (back in the DOS days) because they wanted to avoid division, and use a right shift instead. The answer is close if you are looking at KB (back in the floppy disk days), but not so close by the time you reach TB/TiB. StephenB wrote: Personally I think the power-of-10 units (TB) are more natural.
My recollection is that power-of-2 (TiB) was a Microsoft hack (back in the DOS days) because they wanted to avoid division, and use a right shift instead. The answer is close if you are looking at KB (back in the floppy disk days), but not so close by the time you reach TB/TiB.
Yes, I was aware of that.
I disagree that powers of 10 are 'natural'. Everyone is used to using powers of 2 when talking about memory, and it's a long-accepted standard, as natural to a geek like me as counting from 0, or writing dates as yyyy-mm-dd ;)
I believe some disk manufacturers even use a mixture (or used to), i.e. 1Mb was once used to signify 1024000 bytes... now, that's just as silly as it can get, I reckon!- Well, whichever you think is natural, the mess will remain.
Drive manufacturers (and I believe Apple) use powers-of-10 for storage. Microsoft uses power-of-2 for storage. Linux generally reports bytes, with command line options to do either. Network speeds are always powers-of-10, which creates its own challenge when measuring NAS performance. Memory is always power-of-two.
I try to use TiB for power-of-two storage here, which is the technically correct unit designation. - It is a bit of a mess isn't it? Oh well, as long as everyone knows the difference. You have reminded me of the MiB/TiB etc. usage, which I had forgotten. Thanks for that!
It's a great shame we evolved with ten digits on our hands. If we had ended up with eight, this might have been at least a little easier...
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