Can't re-enable dual disk redundancy

I have a 8-unit Drobo populated with a mixture of 3 & 4TB drives. It has been running with the dual-disk redundancy enabled, but I had a problem recently, so I disabled that feature as a test.

Now I want to re-enable it, but the option is grayed out, so I can’t select it. I’ve tried rebooting the Drobo, but no change.

There is sufficient space to set up a dual-drive redundancy system again, as no data has been added since it was disabled. No disks have been added or removed and the unit is operating normally otherwise.

How can I re-enable this feature?

hi, as far as i remember, that option is only available when enough space is there… but seeing as you have not added any data, it may just be that the process (of changing back to SDR) is still taking place in the background?

im not 100% sure how that process works (possibly like the way it reclaims free blocks), but maybe allowing enough time for the redundancy mode conversion to take place, will allow that option to be selected again once complete?
(if we assume that this would take about the same time as a rebuild, then it may need upto about 1day per 1TB of data that you have).

Thanks for the reply. It’s been 2 weeks since I changed the unit from dual-redundancy to single, yet the dual option is still unavailable.

All components of this system have been rebooted several times, with no change.

When I disabled the dual setting, I expected to hear the typical disk churning that accompanies many major operations, but it was totally silent. I figured the change was only a flag somewhere, so that didn’t seem too odd. The dashboard showed an immediate increase in available space, so all looked good.

The reason I disabled the dual setting was to test a theory about a file copying error I was getting. That theory proved to be wrong, and I want to restore the extra protection, since there is sufficient space to do so.

thanks for the info,
yes, that fair enough about wishing to re-enable ddr.

when you get a moment could you post back some more info about exactly which drives you have (sizes) and the amount of data that you have on the drobo (along with used percentages)… if possible could you take some screenshots of what dashboard is showing you, and to maybe post them up onto imgur or similar, with links to them here?

(if you do though, please remember to rub out any sentsitive/serial numbers to play safe)

I not sure what coding this forum uses, so I am posting 4 screen shots as web links, showing drive sizes and usages. Serial numbers are blanked out:


thanks for the screenshots ian,

as it seems that you have about 15 and a half TB, i would probably try to wait it out and to allow at least 16 days from when it started (possibly adding another day or so depending on how much it was used since then). i say this because (if) it is still completing its change in the background from ddr to sdr, and (if) that process takes about the same amount of time as a relayout, then you are probably almost there.

if you are able to try to wait it out a little more, though in case it is something else which is the issue, can i check what version of dashboard you are using?

(it is posisble that you might have an older version of dashboard, which maybe had a problem with re-enabling ddr, and that a new version of dashboard could be the answer, but likewise it looks like there actually is a newer version of firmware, but i would not try updating anything yet, especially if you do not have a backup of your data.)

if after a few more days or so nothing changes, then another option that might be worth considering, would be to try to see how much a paid ticket might be with support, as they might be able to check your diagnostic logs just in case something is actually having a problem with the drives in some way which is preventing ddr again, (but please do “not” try to capture any diagnostic logs until you have finished waiting, because that can disrupt a rebuilding process and has been known to restart the whole process)

My Dashboard version is 2.5.2 [64171]. As of this Friday, it will be 3 weeks since I changed from dual to single protection. If it is doing any substantial disk writing, it is the quietest disk writing I’ve ever heard.

When I enabled the dual mode the first time, it took (IIRC) about 4 days to complete, and it was noisy. This was with about 2/3 of the data that’s now stored on that unit.

I’m reluctant to update any firmware unless I know the fixed bug list includes a specific problem like this one. I’ve been involved with too many computers and seen too many devices bricked by a simple upgrade.

Support wants $99 to service a trouble ticket; they won’t guarantee this can be fixed; and if it can’t, I won’t get my money back. It seems the support department’s solution to everything is “buy a newer unit,” which is not in our budget. I had a tough enough time convincing our finance department to let me get 2 Drobos, and I told them we would be set for at least 5 years. A year & a half to go!

I just checked the Dashboard again, and the dual option is still not available. I don’t mind waiting another week if that’s what it takes. We’ll see.

it looks like we are thinking on similar lines regarding upgrades in general - (and even on a drobo when i did my first upgrade i actually treated it as a mini-project) :slight_smile: http://www.drobospace.com/forums/showthread.php?tid=2576

it is interesting ian that you only had 2 thirds of the data when you implemented ddr before, though i dont remember seeing anything that would indicate that ddr only worked when the free space value was more than 28% but lets see how things look on friday…

After much time has passed, no change – I still can’t enable the dual-disk redundancy. I tried deleting about 200GB of data, no difference.

thank you for the update,
i was wondering did that bring the free space up to more than 28%?

it might not be feasible to try freeing up more space just to see in case it does need it (since it had ddr before when having that much) though if both drobos (initially had ddr) and are also essentially mirroring each other, then maybe you could try that with backing up some more data though it may be worth trying to get in touch with support again, in case they can work something out, seeing as you bought 2 higher end models, maybe a support ticket could be bought but with smaller multiple installments (which might make it easier to persuade management at work too)?

The free space still shows 28%, but that’s a rounded number, I’m sure.

hmmm, i guess one way to know for sure would be to try and free up just enough space to get it up by 1% (that way even rounded up would still be like what you had before)…

but, i think there’s something awry here… please hang in there as we might need a bit more input from some other users too[hr]
i just had a chocolate… and a thought :slight_smile:

when you disabled ddr (to test if it was a cause of a problem) - can i ask what that actual problem was? (just in case related)

also, can i check how is the drobo shared out with computers?
maybe having things setup with sync or shares (somehow locks it from ddr) as though it thinks it is being used, and maybe trying this when it is not shared out (or maybe at the end of a friday or when no one is needing to map to it and access it, you could disconnect the shares such as from the users computers, and then try again to see if it lets you enable ddr again?)

apart from these - im not sure what else to try (aside from upgrading the firmware which probably needs backups first) or asking about some support installments… (or eating more chocolate)

I’m trying to free up another 200GB or so as an experiment, but that will take some time.

RE: sharing – only one networked computer is accessing either Drobo.

The original problem occurred when I wanted to copy a 2TB external drive to another, identical unit. That would tie up two USB ports if I copied from one drive to another. Since I had ample space on the 8 unit Drobo, I tried to copy the source drive to a temporary directory with the intention of copying from that to the external destination drive. I can tolerate a slow, background operation’s impact on my workflow much better than a fast, intensive op. But I could never complete the first copy, as my main computer stalled during the process, claiming the drive was full.

I think the problem was caused by XP’s 16TB limit on mathematical operations, and caused it to think there was no more space, but before I considered that hypothesis, I tried to expand the available space on the Drobo, so I disabled the dual-disk redundancy, which added space, but did not fix the original problem. Then I was unable to re-enable the dual protection, and here we are.

I removed about 100GB of data from the problem drive, and the dual-drive option reappeared. Just in case it wasn’t because of the data reduction, but something else, like time, I tried several passes of adding, then subtracting data with the free space hovering around 6TB, or 28%. Each time the free space increased, I saw the dual option come back; every time it decreased, the option was grayed out.

So from this experiment, it appears that this model of Drobo cannot enable dual-disk protection even though there appears to be enough space, but it can RETAIN previously-enabled dual-disk protection with the same data free space.

Also, when you go from dual to single protection, it is instantaneous; there is no lengthy process, no blinking lights, and no audible disk activity. I suspect all that happens is a flag is set somewhere. In contrast, going from single to dual protection, there are yellow & green blinking lights for a long time (in my case, about 60 hours) and audible, continuous disk activity can be heard.

ahh am glad your perseverance has paid of (to some extent) in the sense that shuffling some free data to the point where you had ddr before, has at least managed to get you back to that level of ddr (which may still be in progress)

thanks also for the other info about shares and original problem scenario… i still have all my drobo volumes at 2TB max for my use on my or my dads xp machines to back them up etc (plus some other preferences for 2TB max volumes).

fingers crossed, just another 2-3 days and your ddr process will complete, and you can celebrate with a chocolate too :slight_smile:

It’s been 130 hours so far, and the lights are still blinking.

Paul, I’m wondering about your comments about Drobo “volumes.” I am familiar with volumes in a DOS or Windows environment, as partitions, but nothing in the Drobo manuals uses this term. I wasn’t aware that a user could partition a Drobo unit into volumes. Can you shed some light on this while we are waiting for the lights to stop blinking?

ah for me with das drobos, the volumes are essentially just the max volume sizes that we are presented in dashboard when i first set up my drobos. (such as do i want 1TB 2TB 4TB 8TB or 16TB or similar)… i always chose 2TB to be the max volume (for various benefits and also practical reasons such as some computers i hooked up the drobo to, were xp which could not handle huge volumes).

but the max volume size is only used for handling the usable space… for example if i had 2TB of usable space (and with 2TB max volume size), i would get 1 volume, showing approx 2TB max.

if i then grew into 3TB of usable space, such as via upgrading a hard drive, i would then still have my existing volume, but a new volume would be made, also showing 2TB free. (in essense that new volume would only actually have 1TB of extra usable space, but is presented to the operating system as 2TB via thin-provisioning for the future).

in reality, i could put about 2TB on the 2nd volume, and only about 1TB on the first volume (but i would need to make sure not to exceed the 3TB actually usable space across both volumes, and dashboard would show me the most accurate representation of how much free space i have on the drobo in general… which is what you dont want to fill up)

the only extra thing that also exists for some versions, is the ability to create a special extra volume (relating to time machine backups) which i dont believe is tied into the max volume sizing above, though i do not use it or a mac.

For your current rebuilds though, i would still try waiting, (and also closing down or stopping any other programs that might be running, as those can slow down the rebuild process…
does dashboard show you any values for its estimated time remaining?
the only other thing i can suggest would be to try shutting down the computer, and then if no activity lights are flashing for the computer activity light on the drobo for 5mins, you could then unplug the computer connection cable from the drobo, which may help to fully eliminate any potential slowdown activity from the computer…

… but please be sure to unplug the computer connection cable (and not the power like i once did by mistake) :slight_smile:

It took 200 hours (9 days), but the rebuild has now finished and the lights have stopped flashing. There was very little I could have done to speed this up, as the unit was under very light and infrequent access during the rebuild.

It’s disturbing that it would take so long. What would have happened if I had a lengthy power failure during the rebuild that my UPS couldn’t handle? Would I have lost all data, or would it merely have caused a restart of the rebuild?

Regarding the volume question…I don’t see any such options in my Drobo setup, and I don’t recall seeing anything about volumes internal to either of my Drobos, ever. I can only conclude that we are using different software or else I am overlooking something.

Whenever I upgrade from one disk to a larger one, I see no volume choices; the new capacity is added to the old as a single volume. Not that it matters; I’d prefer not splitting one Drobo into virtual volumes, but it does make 16TB the max that XP can handle as a single drive letter. Over a network, the 2TB single-volume limit is not applicable.

Ok, sorry i missed this thread earlier…

Your assumptions are correct.

Drobo will not permit you to enable dual disk redundancy… IF, when DDR is enabled, it will put you be in a “low space” condition… (i forget precisely what that is … but basically when one light comes on yellow - maybe 20% free?)

So you could be quite happily using DDR, and your drobo, and living with the one yellow light, because in fact that is still quite a lot of free space, especially on the 8 drive units, reading and writing and everything is fine and you have DDR on. but if you disable DDR while you have a low space condition, then you can’t renable it without first removing some data because that will take you back into the “low space” condition (even thought you were there previously).

Disabling DDR is instant - it simply marks all the space occupied by the second rotate parity as being free (in essence it deletes that second disk’s worth of redundancy)

Enabling DDR require drobo to recalculate a second lot of parity for all of your data and then writer tit all to the disks - so obviously that will take quite some time.[hr]
Oh, and its not just THAT model - thats the same for all Drobos which can do DDR… you can’t ENTER a low-space condition by enabling DDR, it just wont let you. But you can happily operate in a low space condition with DDR enables, or disable DDR to leave a low space condition.[hr]

Lets be careful with the language here. it wasn’t an actual “rebuild” in that it wasn’t rec-recreating any of your data.

it was creating some secondary parity data. even if all of that parity data was somehow corrupted by a power issue… you would still have your data intact and your first lot of parity data.

You could always shut it down manually if you needed to (assuming you were there of course), it wouldn’t have minded that.

If the UPS had exhausted its battery and simply cut power - you would not have been in any different situation than if you had lost power during any other read/write situation. (Drobos do have an internal battery to protect the write-cache in case of power failure)

it is unfortunate that the model cannot interface with an UPS to shut itself down when the battery is low, but that is a general observation on the design of the model and is not specific to your situation

hi am glad it finished successfully and your patience in waiting paid off :slight_smile:

also thanks docchris for a lot more info about the process, and terminology for parity.
(did i mention that i learnt a lot from from docchris and others over the years, and i sometime refer to him as a master jedi - says paul the padawan) :smiley: