Any slowdown before reaching 95% of capacity?

According to the documentation, when you have filled the usable data on your Drobo to 85% you get an alert about your space filling up and one of the drive bays will show a yellow light, indicating that you should upgrade it with a higher-capacity drive when possible.

And again, according to the documentation, when you have filled the usable data on your Drobo to 95%, you will get a critical alert, one of the drive bays will have a red light, and you will see a noticeable decrease in speed (read? write? both?).

I have hit the first, non-critical alert and yellow light for reaching 85% capacity. I guess what I want to know is:

  1. If I want to get the most use out of my Drobo, can I continue to fill it to just under 95% of capacity without experiencing slow-downs? In other words, is the yellow light and first warning simply a friendly reminder to keep an eye on things and plan for future storage needs, or will there be any decrease in performance from the Drobo before reaching 95% full?

  2. Is the slow-down when reaching 95% something imposed in software/firmware to get our attention, or is it something more “natural” that happens as you approach the upper storage limit, and it just becomes more noticeable at about 95%?

  3. When the slowdown (at or around 95%) occurs, does it occur on read operations, or write operations, or both?

Thank you for your help.

The flashing yellow light means now is the time to add capacity…not later.

Maybe I should have explained better, but I have no intention of adding capacity to this Drobo–not now, not ever. The capacity is already big enough for what I use it for. Its primary use is as DVR storage. My DVR stores movies and TV shows to it. Every so often, I do some housekeeping tasks, including deleting TV shows and movies that I don’t think I’d ever watch again. I’m perfectly capable of monitoring and keeping the data I have stored on it under some fixed limit by adjusting the criteria I use when I’m making decisions on what to keep and what to purge. Further, I don’t have to worry about others exceeding capacity–I’m the only user.

To give even more detail about the question I’m asking, I have a Drobo 5N with a 4 TB HDD in each of the five bays for a total of 20 TB (18.19 TB actual) raw storage. With single disk redundancy and normal overhead, that gives me 14.35 TB available for my data.

The yellow light comes on when I reach 85% of that capacity, in my case, at 12.20 TB. I’ve been just over that threshold twice. The first time, I was curious about whether the Drobo would get rid of the yellow light and go back to all green if I deleted a few things, so I did my normal purging tasks to bring the total data stored on my Drobo to under 12.20 TB again. Sure enough, the alert went away and the lights went all green again.

So, now that I’m just a bit over that 12.20 TB threshold again, the yellow light and the alert is back. Nothing terrible has happened though, and I’m not feeling compelled to try to make go all green this time. The Drobo seems to work exactly the same when it is filled to 86% capacity, as when it is filled to 84%, other than the color of one of the lights, and the alert that pops up when I run Drobo Dashboard, and the email that it sends (because I’ve configured it to send email on alerts).

I recognize that it may make some people uncomfortable that I don’t run out and buy a bigger hard drive just because the light came on, but as I said, the capacity is enough. I just want to know how much of the “available” space on my Drobo is actually available for me to use before I notice anything bad happen other than a light coming on.

The next threshold, according to the docs I’ve read, is reached when you’ve used 95% of the available capacity. (On my Drobo the 95% threshold would be at 13.63 TB, or 1.43 TB more than the 85% yellow warning light threshold.) And although I haven’t reached that point yet, according to the docs when you do reach 95% of capacity the warning light changes from yellow to red to indicate that space is at a critical point, and a noticeable slowdown occurs.

To me, 1.43 TB is a significant amount. If I can use it without experiencing anything negative, I want to. It would be the difference, for example, of deleting 700 movies, or keeping them. I’ll delete them if I have to in order to keep my Drobo running smoothly, but do I have to? At what point will anything that’s not purely cosmetic happen if I continue to let my data creep closer to that 95% mark? Is the slow-down described in the documentation at the 95% mark something that is purposely coded into the firmware (which I think is a reasonable thing to do to make it harder for an admin or user to ignore), or is the slowdown caused by something else as the data approaches the usable capacity, in which case I might expect to see it gradually get slower earlier than the 95% mark?

I’m not being completely careless. I have this stuff on a Drobo because collecting it did take some time and effort. I have another new 4 TB HDD in my closet–one that matches the five already in the Drobo. When the day comes that one of the drives goes bad, I’ll immediately replace it with the one in the closet and then buy another backup drive. Over time, it’s possible that the capacity in this Drobo will go up because the replacement drives I buy may be bigger than 4 TB. But I’m not interested in upgrading the capacity just because I’ve reached it, because the kind of data I have saved on it really isn’t critical, and I regularly delete things from it anyway.

Hopefully, that helps clear up what I’m asking and why. So, AzDragonLord, do you, or anyone else reading this know? Do I really need to keep the data I have saved on this Drobo under 85% of the “usable” capacity (under 12.20 TB) or can I use closer to 95% of the “usable” capacity (13.63 TB) before anything bad happens?

Thanks for exploring this with me. If nobody can give an answer, I suppose I’ll experiment with it myself, gradually letting the stored files climb from 12.20 TB to 13.63 TB, and take notes about what I notice and when.

The slowdown at 95% is write speed.

[quote]The flashing yellow light means now is the time to add capacity…not later. [/quote]it’s solid, not flashing.

Thanks, reckg! That answers the third question from my original post. Have you run into that yourself? Did you see any slowdown prior to reaching 95% capacity?

Does anyone know the answer to the other two questions from the OP?

hi harvv, here are some thougts from me too,

if we take the default setup, starting out at 2 drives, then “some” slight performance hit will be encountered with each additional drive. (i believe this is also the case with other devices too, and something to do with how different types of parity and protection scale up)

if you happen to get a yellow light for a drive (and more details in dashboard also happen to show a message label for it, like warning or healed, then i would try to change it even if yellow where possible)

as far as i know the 95% full, usually slows down any device or even stand-alone drives to a degree (though in the drobos case i think each percent slows wirtes more to try to prevent overfilling as much as possible), generally though i think something do with with filesystem overheads trying to find and use empty sectors/blocks. (if you have ever tried a microsoft defrag on a fairly full drive, it used to give some popups to try and disuade the user from defragging a drive unless it had 6% free) :slight_smile:

the only thing possibly more annoying than that, is getting greeting by a friendly Mister PaperClip cartoon character, after you click on cancel defrag, saying “hello, it looks as though you are trying to run a defrag… etc etc, click here for additional information for Defrags here, or click here to minimise me and send me to timbucktuu” :smiley: