Totally erratic throughput with huge peaks and canyons

I was wondering why I kept getting crackles and pops when watching videos, and I just tested my unit with AJA System Test.

I have set “Disk Drive Spin Down” to never, the unit is powered 24/24 7/7 and have this issue with iSCSI, FW800 or USB2.

Regardless of connection used, I always get huge peaks and canyons from 70 to 90 mb/s (depending of connection) to < 5 mb/s. The simple 3.5" HD inside the iMac (late 2009, a state of the art Mac under 10.6.3) I’m currently using is a model of stability by comparison.

WTF? not exactly what I was expecting from a $1500 storage device.

Added some pics outlining the problem (currently connected through FW800).


System disk

latest firmware?

Yes as far as I know.

how long has it been since you either set up drobo, or wrote a lot of data to it - sometimes after a large change, it can take a day o two to settle down.

aside from that its hard to say. im on windows 7 with a 16TB 'pro over iscsi and i can stream two blu-ray streams at one flawlessly

Unfortunately this is relatively normal for the DroboPro

As long as you have the latest firmware and its been running for a while the system should be stable.

From what I can tell the trouble with these tests is that they are pushing more data into the drobo than it can contain in its write cache. And as its got this strange sort of raid protection it needs to write out and validate the data before moving on. Hence when writing large amounts of data you get the sudden drops in transfer whilst the drobo catches up. This I think is because something in the Pro just isn’t quick enough to cope. Thus we have the updated faster DroboElite that I assume does a better job. Feeling jipped yet?

Of course this is not confirmed by official sources, just what I have surmised from my use of a DroboPro over the last year ish. It works reasonably well on normal files, but you start shifting GB files around and it sucks pretty fast. Fair play to DR they have improved the firmware vastly since launch, but I suspect they are up against their design flaw now that bottle necks the shifting of large media files around.

I stand ready to be corrected by a firmware release that solves this and makes the DroboPro work better - please.

the original poster is talking about READING not writing (i know his benchmarks show both) - he is trying to playback video FROM the drobo.

Saw the pictures didn’t read the words properly. Very embarrassed.

Patchy reading isn’t something I have noticed, although it still doesn’t read as fast as I think it should. A support case is the best way to go on this one for sure. DR have always been very good on the support side of things when I have had cause to open a case.

What format and bitrate is the video you’re playing back?

When was the last time your ran repair disk on your volume?

Also, please open a support case.

@bhiga: 15 Mbps

The volume is fine, at least as far as Disk Utility is concerned, and the unit is brand new. I tend to agree with jstrat that the Pro is simply underpowered to ensure constant high throughput as a primary storage device. For sure it hates concurrent access, if I write something big to it, I can forget trying to read anything from it that is throughput sensitive. With the same drives in a RAID-6 configuration, my former Areca 1221x controller simply annihilates it on the performance front in every possible way.

I still like BeyondRAID’s flexibility regarding migration and rebuilding thought, and it’s a rather silent device for 16 TB of HDs configured as dual redundancy, but performance-wise the hardware kind of suck and really doesn’t cut it.

I hope that some future firmware will improve performance and that DRI Management is listening, but I just bought today a QNAP TS-859 Pro to use as my primary storage device, instead of a 2nd Drobo like I initially envisioned. It’s less flexible to switch around HDs but also offers more stable/higher performance, multi-iSCSI initiators and jumbo frames support…not to mention just more features at the same price point.

Granted it’s a bit Apples vs Oranges but we have a DroboPro connected to a Dell Zino HD system (AMD-based, ATI graphics) via iSCSI and we get 20+ MB/sec transfer, so we’re seeing waaay better than 15 Mbps.

I agree that concurrent access does slow things down quite a bit.

Well max throughput is one thing, but I would like for stability also because at time it falls under 5 Mbps, as if I was using a USB flash drive device.

open a support case, it should be better than that.

I will, but I want to perform more tests and better document them. I still think the Pro just lacks the raw muscle to ensure a constant throughput.

well like i say, i can run two blu-ray streams off mine, flawlessly and simultaneously over iSCSI,

depending on the application - can you increase the buffer since your average throughput should be high enough? it just needs to cope with the occasional stutter more gracefully

Good idea thanks!

Indeed I’ve boosted the latency in VLC, Vox, iTunes and it works, but it kind of sucks to have to resort to such subterfuge. Even playback of a 1 Mbps FLAC file is not perfect with the default caching setting, which even a low-cost HD can ensure without fuss.

The Pro might be reliable, and I will take over that unreliable POS QNAP NAS, but for the price I’m not very impressed by its overall performance - and that’s an understatement. :-/

DigitalFury - I am trying to send you a private message but I am told my account is not activated (it definitely is). I’m keen to know what you thought of the performance from the QNAP 859 compared to the DroboPro.

I get about 20Mbs throughput, but I have some issues with large file-writes (I’ve posted a thread on the forum about it).

Obvious the connectivity is key, I am currently using a 1GB iSCSI connection to a Windows server via a switch, sharing the volumes from that, to a Windows 7 client on the same host (ESXi 4 host running the server and Win7) and notice the shared drive mapping on the Win7 client drops out if I try and write a large file (8GB+).

I’m going to get another network card for the ESX server and have the iSCSI connected directly to the server, and the other card going to the network for SMB. I.e. maybe the switch is just a not quite up to it.

Still, I’m wondering what you think of the performance generally (regardless of connectivity) compared to the QNAP.

Overall the performance of the QNAP was better than the DroboPro under iSCSI, but I had so many issues with it with a Mac OS X client, that I couldn’t test it properly and already returned it for a refund.