Mounting options and performance concern


I have a Drobo, FW to a MacMini for media and TM Backups for three other Macs. In effect making the Drobo a NAS by using the MacMini (which also runs iTunes, keeps things up to date etc.)

I also have a music library on the Drobo, which is accessed by my Sonos system. I am having problems that when a Mac runs a TM backup, and I have music streaming - the music jitters then just stops. Whilst I get around 30MBytes/Sec from the Drobo on FW I was wondering if the Pro via iSCSI would be better? It isn’t related to the Mini, as another single FW drive doesn’t have this problem (just lacks the size and resilience).

So, onto the questions:

  1. Would a DroboPro, fronted by a MacMini be able to handle a couple of Macs with different, concurrent, access? Ideally via iSCSI or FW.

  2. Could a DroboPro be mounted on it’s side, so it was 8 drive bays vertical? I have very limited space, a Drobo v2 is just the right size and OK noise wise. If the DroboPro would work, I need to fit it into the same space.

Anyway, glad for any feedback.

  1. drobo slows down dramatically with concurrent access - regardless of interface
  2. its not recommended

This is what I feared.

I quite like the Drobo for it’s noise and simplicity, alas not its performance.

Looks like a plan B is going to require investigation into other devices.

Are you using FireWire 400 or FireWire 800?
FireWire 400 is half-duplex (i.e. it can either send or receive but not both at the same time). This makes it far far worse for concurrent access, especially when TimeMachine writes lots of files.

Also if you do have a Mac with Firewire 800 check to make sure it is actually running in 800 mode and not at 400
See article: http://support.datarobotics.com/app/answers/detail/a_id/98/kw/firewire/r_id/100004

With a regular drobo that will make almost zero difference

when reading and writing simultaneously the performance will fall well below even half duplex FW400

Yes, all running at FW800. I get normally 32Mbyte/Sec on writes, and a little more on reads. If only one thing happens at once.

Another example, all running on the directly attached MacMini. iTunes is ripping a CD in lossless, with iPhoto importing some pics (these are 20Mb raw files). If only 1 is working, all fine. If both are working it makes both tasks stutter and stop for short periods. If you use iStat and watch the disk IO there are bits where it just drops to zero for a second or two. As if the Drobo needs a little time to settle before moving on.

If I attach a single FW800 based drive (Seagate Freeagent portable) and do the same, no problems at all.

I was wondering if the iSCSI side would be better from the Drobo’s point of view, but it seems not.

Probably best not to invest more in the Drobo route, which is a shame. Seems like a great bit of tech, just needs to get the performance side sorted out.[/align]

Apparently its related to how drobo maps the virtualised sectors to physical sectors - it can only hold part of the table in its memory, so if you are working with two differnet files, then it needs to load th table, work with the file, then load a differnet part of the table to work with the second file.

i hope that made sense!?

Yes, makes that does make sense. Seems easy to solve really, RAM is cheap!

I’ve boxed the Drobo up, will return it next week. Whilst the feature set is great for what I need, the performance is just too poor.

Now, just have to get the receipt out of Santa, this is going to be interesting…

Did you try DroboPro firmware 1.1.4 which addresses some performance issues?
It is available on the suport page http://www.drobo.com/support/updates.php (not yet available via the Dashboard auto-update).

I have a DroboPro mounted iSCSI on a 1.82 GHz core 2 duo Macmini. Performance from the mini to Drobo is around 65 MB/sec. Performance sharing it via afp on a network is around 55MB/sec for other Macs.

If you want performance from DroboPro, use iSCSI. From what I’ve heard and read, its FW800 performance is about the same as gen2 Drobo.

I only has a Drobo v2, and was looking at possibly the pro to solve my problems.

Switcher, can you run a tv stream from the drobopro and copy to it OK? We often have a few music streams running through a Sonos system, if any of the macs starts a TM backup the music will stutter and stop with the drobo v2.

From your experince with he Pro, how does it handle being asked to get various reads and writes via AFP o the macmini?

I can play back a blu-ray (about 30mbits/sec) from my 'pro - while writing a large file to it, and it can cope with that. i wouldnt want to try more than 1 read = 1 write simultaneously though

That is interesting, I will have four zones on the sonos playing different tracks - all in apple lossless format. How would the pro handle that? it isn’t so much about raw throuput but more responding to a read request if another interactive stream starts (such as a TM backup) before the buffers empty on the sonos.

I have a netgear nas, which works ok speed wise but lacks real mac support. I get lots of niggly problems with file copies etc. Either das or iscsi das seems the best approach, the netgear stuff will icsci ( not my version ) but it is limited to 2tb volumes.

I was mulling an apple tv, which would eat disk space. Hence looking for a new solution. Much to think about…

im not sure, really its suck it and see, i dont have any apple lossless to try with, i could probably try playing back 3 dvd streams at once to my 3 machines, but my pro is rebuilding so probably not up to it at the moment

I suspect the Pro would work OK, all the music does is open four 20-200Mb files and read them in small chunks as the music plays, at roughly 250Kbits per stream. When I did this with the Drobo V2, then started a copy to it it could not handle the reads at all - it just seemed too busy handling the writes.

I got a tweet from Drobo about a discount, but despite many attempts to contact them with no luck, this does seem to be US only code. Perhaps I will get one in the new year and give it a try. As I’m in the UK, I will have to shop around.

I noted that the manual says don’t mount on its side because of possible disk connection problem. Odd, that the same orientation is used by the Drobo and Drobo S. I could only mount it on its side (with the addition of suitable feet), given I have no space at all to put it anywhere else. I liked the way the Drobo v2 was quiet, then spun the fan up as required. Most of the time it was almost silent.

well the fact that the orientation is used by the drobo and drobo s is irrelevant since the internal supports would be designed to hold the drives in that position - the drobo pro and elite are designed to hold their drives horizontally

it would probably work, but that info above is corporate code for “we told you so” if it all goes wrong

@rjc You have your pro situated on it’s side? Where the drives are laying flat instead of horizontal?

No, I don’t have a Pro. I had a Drobo v2 but sent it back because of performance issues. I started this thread wondering if the Pro would be a better option - which led to the question about orientation.

The Drobo (v2 and S) have drives horizontal, or flat, as seen in most PC’s etc. The Pro has them vertically, as seen in most rack based systems to give the best density.

I don’t have physical space to put a Pro in its default orientation, but I have a space where the Drobo v2 was sitting - which has plenty of space vertically above it. Hence the question about orientation. The drives themselves have no issues, it would just be how the Pro’s bays are constructed. Possibly some thermal issues too I guess?

It sounds like the orientation is looking like a show stopper, is this the case?

Yes, if you put the Pro on it’s side, so the drives are laying flat you can actually cause damage to the back plane where the drives connect to it.

Co-worker is using his pro as a base for his monitor. Saves a lot of space on his desk.

Thanks for the info, but I’d have to put a 27" iMac on top of it - which would then be too high up to use without discomfort.

I’ll make a mock up of out of some card and try a few places, but space is a premium for me. Just going from a PC and 19" tft to the iMac has led to some problems. I was looking to use the space where the PC lived to house storage & my MacMini.