Added 5th drive, speed drops 20%?

I have been running my 5n for a while now, with 4 drives (all 4tb) and 120gb mSATA, my average read speed was about 90-95MB/s.

But I recently just put in a 5th drive, Toshiba 4tb 7200rpm and my speeds dropped to 60-65MB/s.

I noticed the speed drop before the recent update, and the update didn’t seem to effect it at all.

My question is: what did i do wrong? i went with the fastest drive i could get yet it still had a large negative impact on the transfer speed. I know the original 4 drives are 7200rpm and the new Toshiba drive i just put in has a bigger cache then all the original 4? (the drobo is not rebuilding the array or anything like that, green lights across the board)

Ideas? thanks

Since BeyondRAID is proprietary it’s hard to say, but some RAID systems will drop performance as they try to prefer the new empty drives for data, seeking to balance storage across the array. Long-term it’s a good idea - you want your drives to be as balanced as possible for maximum parallelism - but it can crush your performance in the interim. Now, I don’t know that the Drobo works in such a way, but it would be consistent with other similar raid designs (e.g. ZFS).

The speed impact might be intermittent as a new drive was added into the pack (array). When a new drive added into the pack, Drobo firmware immediately absorb the drive and increase the total free space. As we all know… this is a new drive added to existing pack (array)… parity has to be calculated for the new addition drive. So this might impact the speed.

*Drobo firmware might not totally “works” as liked I have described but should be more or less…

So wait for a few days…(depending on the amount of data)… and see if the speed goes back to normal.

I put the Toshiba drive in well over a week ago, i just didn’t notice the speed reduction until the other day just before the firmware upgrade.

I know with the verity of drives out there it can be hit or miss… i can find another home for this Toshiba drive, however i dont know what to look for in a new drive to ensure i get my 90mb/s back?

that 90mb/s is very important to me (reason i switched from the my 2nd gen USB)[hr]
Is there a way to test each drive? i just noticed one of my original 4tb drives reports as “healed” under the health category in the drive information section.

Perhaps one of my old drives ran into problems at the same time i installed the new one? again no red lights but if the drobo “healed” the drive perhaps at a speed cost?

hi apeg,
as i was reading through the posts, i was thinking along similar lines to don and diamond in the following ways, eg:

a) as far as i understand it, each extra drive (especially after the 2nd) added to an arrary (of most types; drobo or not) will add a bit more overhead as part of parity for protection. (if that is the case, then ‘some’ slowdown may not be able to be avoided, but some people have mentioned that using drives of the same speed could help, as you have, or all the same model could help to mitigate a little?)

b) also, while drives could be ok and green for example, when a new drive is added, it will still need time to get some data onto it and if this happens behind the scenes, it may not be visible that it is still taking place. (drive chatter and vibrations could help to indicate a bit though). Im not 100% sure as to how long that process will take, and possibly it is done as a background task, but maybe taking the time of a rebuild into consideration, at 1day per 1tb of data that you have might work. am not sure how full your drobo is or if you only have SDR, but maybe a couple of weeks to settle.

c) newer models of drobo (and probably all of the officially supported ones) have data scrubbing features that take place from time to time to help verify the integrity of data. if i remember correctly from docchris, it tries to scrub every month, usually during idle time, unless it wasnt able to find enough idle time. (maybe this process kicked in as well, adding some more slowdown until it completed/completes)

but, now that you mention healed. thats interesting too :slight_smile:
maybe you could let things settle a bit more, and then after when all are still green etc, you could try taking a diagnostics file?

Thanks Paul, that makes a lot of sense.

Right now 60mb/s is more than enough for my needs, so ill give it some time… but in a few months that need may change.

that additional overhead per drive does make sense, but it would be a shame if that’s the cause. Anyhow ill let go a few more weeks and test speeds some more in hopes that it settles down.


ok sure, it would be good to know how things progress,
in the meantime, that gives plenty of time to have several snacks :slight_smile:

The plot thickens…

While i was at my computer the drobo dashboard came up with the red alter box saying “i have currently no drive redundancy”, then almost immediately to a yellow box saying its rebuilding and before i could even load up the dashboard it went to green.

so im guessing a drive is on its way out, and perhaps the drobo “healed” it again? all signs point to the top healed drive, but are there logs or anywhere i would see which drive hiccuped before i replace the obvious culprit?

on a side note, this is good news reguarding the speed issues, could just be one of the drives is on its last legs slowing things down.

hi apeg, i think youre right,
while the healed is also shown in dashboard, its also good to see that mini-rebuild with your own eyes too (if a little daunting) :slight_smile:

when one of my wd15eads drives failed after 4-5years, it also caused some sluggishness beforehand (plus o/s crashes)

im not sure if there are any logs that you yourself could review, but as the 5n is relatively new maybe you can take a diagnostics log via dashboard and to post a ticket for support team as they should be able to help determine more info about the problems that a drive is having from the logs.

Very nice, I didn’t know you could get diagnostic logs.

the “healed” disk reports as “0x11” for disk state (not sure what the means but the rest are all “0x10” and its Error count is 6… that’s enough evidence for me to swap it out.

Thanks for the help guys… ill let you know if the new drive solves the speed problems.


We’ll i finally had time to swap the die(ing) drive and my reduced speed remained the same?

This is very disappointing as i purchased the 5n for its speed over my original 4 bay, all i have done is put in 7200rpm (fastest i can find) drives. Why would that result in my speed going from 90->60 MB/s?

I was originally getting 90MB/s with only 4 drives, was the reduction in speed a result of the addition of the 5th drive and the speed of the drive(s) have little to do with it?

IF SO: this would be valuable information to convey to your customers, it would have greatly changed the number and size of the drives i purchased… far too late now

This is read speed you’re talking about? Try removing the mSATA card.

Yes, read speed. copying from the Drobo.

you think the mSATA could be slowing things down? ill give it a shot

There are certainly cases mentioned in these threads of mSATA cards causing slowdowns. Many people find they make little if any noticeable improvement and many have problems with them. It’s easy to try going without and it might improve your situation. Make sure you power down first.

So i finally had an opportunity to remove the mSATA and test… sadly it would seem the mSATA wasn’t the result of the slowdown, but even more concerning it didn’t seem to make any difference :-S slightly disappointing as i remember spending over $100 for the mSATA at the time of purcahse.

A little heads up to the user would be nice, no one wins if i waste $100+ dollars to some mSATA company :-S

I have a feeling its the addition of the 5th drive that caused my slow down… and i dont mean my 5th drive is slow, its the same RPM and the largest cache of all of them. But just having ANY 5 drives, i wonder doing the work for 5 drives causes problems vs. only 4 when i was getting my 90-100MB/s

Is there any way to test that? i guess i could pull a drive (at my risk) and see what speeds i get then? but thats not exactly the most controlled test

Might be a silly question, but how did you measure the read spead? Copying a large file while being connected to the Drobo 5N via a LAN cable or did you use a tool?

Hey titan3025,

I have the Drobo 5N connected to my gigabit switch, at the same time my computer is connected to the same switch via gigabit.

The issues was originally noticed only when copying large files to and from the Drobo. Prior to adding the 5th drive i was getting ~90-100mb/s all the time. After adding the 5th drive my speeds dropped to ~60mb/s.

Since then i have tested with tools like “NAS performance tester” which provide identical results to what i’m seeing with standard copy/paste.

So, I have a similar config to you. 5 drives and mSATA. I used Disk Speed Test on my Mac to measure the performance (Gigabit ethernet) and was getting 85-95 MB/s write and 95-105 MB/s read. I think there may be something else amiss with your setup and adding the 5th drive was just coincidence.

Have you tried…

A different switch? A different ethernet cable? A different computer? Voodoo?

These types of problems can be NERVE WRACKING and it always seems like the solution is something so simple it shouldn’t have been the solution.

Thanks for the suggestion, just seemed so well timed with the 5th drive add-on. unfortunately i’m away from home more than i’m there… so the cable and Ethernet cable switch test will have to wait a week. but I’ve tried a different computer with no change.

Ill see what i can do via Voodoo lol

hi, it may just need a bit of time to optimise and relayout some data in the background,
(eg if you have not been adding, changing, or deleting lots of small files, and have not filled it up much then if you try letting it settle a bit, it might improve again?)[hr]
having said that, using 5 drives rather than 4 im sure would add (some) kind of overhead, simply as the whole system is now needing to manage an extra drive, but see how it goes after a couple of days.