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  • Hey all, just changed over the backend after 15 years I figured time to give it a bit of an update, its probably gonna be a bit weird for most of you and i am sure there is a few bugs to work out but it should kinda work the same as before... hopefully :)

USB Transfer Speeds?

A

Alexis Hanawalt

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I'm trying to figure out how well the Drobo (http://www.drobo.com)would stack up for overnight backup of Redcode media - the USB issue still boggles me. I can't find much information on actual sustained transfer rates other than this somewhat old benchmark test: http://www.g4tv.com/techtvvault/features/39129/USB_20_Versus_FireWire_pg3.html - If this is still accurate, you wouldn't be able to backup much more than 100Gb in a night. Are there more recent, faster benchmarks out there that anyone's seen?
 
FWIW, I ordered a drobo about a month ago. I received it and was so excited to give it a try... It was defective, wouldn't mount on three separate systems (1 mac, 2 PCs). I bought from newegg, who wouldn't accept a return for it. I usually like newegg, but they do this on some products they sell sometimes and it can be aggravating. Anyway, had to deal direct with drobo for the return, not a big deal, i had a replacement in two business days.

The new one loaded up and I dropped in 4x500GB Hitachi hard drives. Everything seemed just wonderful. After about 4 hours of copying stuff and playing with it, the drobo unit seemed to just lock or hang.... No response. Finally had to power down and reboot the system. Never got the drobo to re-mount on that system or any other. I sent it back to drobo. While they were very gracious in their service of getting me a replacement. They initially balked at a refund because I bought from newegg, who refused to take either drobo unit back. I did eventually get my purchase amount refunded from drobo, but it was a hassle.

I'm still very interested in this product as it looks promising. But I'll wait for the second generation of the product -- if it makes it that far. Hopefully they'll have the bugs ironed out and will offer other interface choices like gig-E and/or eSATA. I think a gig-E NAS drobo would be awesome.
 
A few other comments about drobo that I have...

It runs HOT!!!! It seems that this is one of the biggest complaints of other users in their forums. There are people making independent lists and comparing notes over which drives work well and which don't due to heat. The Hitachi drives I used are on several lists of drives that supposedly work well. I think they could have used a more compact and efficient power supply and better cooling design to deal with this. However, it's obvious that they were shooting for maximum capabilities in a bargain basement price. I think they may have shot themselves in the foot here. Lots of reports coming in saying that fast drives like 10K and 15K rpm units will overheat drobo, often causing permanent damage. Not that there's any point in using such drives as drobo won't benefit. Reported speeds are somewhat slow too. About 40 to 45 MB/s with fast drives, which indicates that the limiting factors are probably both internal components and bandwidth and the USB interface -- USB2 tops out a theoretical max of 56MB/s anyway. Latency is quite high with drobo and I definitely noticed it with my unit.

DOA units seem to be very, very common. Not a good sign for product longevity and reliablity, or quality-control.
 
I just watched the video and am perplexed at how in the world it is keeping your data safe without using any kind of raid system. It was an impressive video, and if Jeff thinks it is worth looking into, then it probably is. I personally am going to be using a raid 1 external drive and a tape backup (for permanent storage) to hold data while it is being transferred to a server with raid 6. So at no time will there be less than 1 copy of the data after it is transferred from the red drive or CF.
 
kinobairn said:
I just watched the video and am perplexed at how in the world it is keeping your data safe without using any kind of raid system.
Click to expand...

It is using a RAID system... It just handles it transparently to the user. When you add a new drive into the system, it copies and/or redistributes data across the drives... It's very similar to a RAID-3 configuration that is entirely dynamic, it's pretty cool.

For now though, I would approach drobo with a "buyer beware" attitude. It's a great idea, and looks to be a good implementation. Unfortunately, the actual production quality and reliability of the unit seem to be in question. I would not trust drobo in a production environment right now or to be my only means of mass storage or data backup for anything significant.

I will definitely give drobo another chance after it matures a bit. One thing that does concern me is there are still lots of bugs and issues with their software tools, but no software updates since early May. A little concerning for such a new product that is supposedly in continuous development.
 
RAID is just an acronym for REDUNDANT ARRAY OF INDEPENDENT DEVICES. So in actuality, for them to claim it's not RAID is misleading and they are most likely trying to build up a product to sound better than it really is to the less technical crowd.

As far as I can tell, it works just like a dynamically allocated, concatenated RAID-3 array with a very large block interleave pattern. The concatenation allows the volume size to be instantly increased by dropping a new disk in place and the large block sizes to shift redundant data around more transparently, but at a performance hit. The performance hit isn't really noticeable since the system itself is pretty limited on external bandwidth. There are several RAID products on the market that work just like drobo, but require more user intervention when adding and removing drives. Drobo's real innovation is in the transparent and automated management that makes it ideal for end users.

RAID levels or common definitions of such (RAID 0, 1, 2, 0+1, etc..) have evolved over the years by certain methods being placed into use and many people adopting them if they found them useful. Exact implementations can differ from one manufacturer to another. RAID levels 0 through 4 can exist on single volumes. And there may be good reasons to do so for nested RAID configs.

Drobo isn't always going to work as quick as what's shown in their demo video when setting up new disks. They didn't have much of anything on that drive and the system paces itself -- he would only leave those disks in for a minute or so when swapping for the demo. But if you have 2x500GB drives in there and they're full (roughly 460GB of actual data after the format and the drobo/RAID overhead) and you place another 500GB drive in there, it will initialize after a few seconds and show the drive as "ready", upping the available capacity. But drobo will spend the next several hours or days actually transfering data blocks around, as transparently as possible until the full RAID is reconstructed across the three drives. Any of those three drives can be failed at any time, even after the third has only just come online due to how it dynamically shifts blocks and spreads data equally. ...Same for a 4 drive config, any one of the drives can be failed at any time. In a single drive config, obviously all the redundancy is on the same disk... so not that secure. In a 2-drive config, the data is redundant only after drobo has completely rebuilt the array, and only then can either disk be failed. Until then, only the secondary disc can fail and data be retained... Their demo video does not show this.
 
Okay, I'm staying the hell away from the Drobo.

Back to the question of transfer speeds - it still seems baffling to me that countless websites agree that USB is basically as fast as Firewire, yet won't transfer the same amount of data in the same time. The theoretical limit is meaningless - what's an average?
 
usb/firewire speed

usb/firewire speed

Cinewalt said:
Okay, I'm staying the hell away from the Drobo.

Back to the question of transfer speeds - it still seems baffling to me that countless websites agree that USB is basically as fast as Firewire, yet won't transfer the same amount of data in the same time. The theoretical limit is meaningless - what's an average?
Click to expand...

all of the speed comparisons are meaningless because the drive rpm, cache and chipset determine the speed of data transfer. usb and firewire are just the transfer means.
 
USB 2.0 spec has a maximum bandwidth of 480Mbps
FireWire IEEE 1394a (aka, i.Link or Firewire 400) has a max of 400Mbps.
FireWire IEEE 1394b / FireWire 800 has a max of 800Mbps

The three of those are 60MB/s, 50MB/s and 100MB/s respectively.

So, on the surface, one could say that USB2 is better that Firewire 400... But like Wigby said, it all comes down to the drives used, chipsets, etc.. We also have to look at computer systems and the host chipsets and implementations there. PowerMac G5 systems prior to the G5 Quad had pretty shoddy USB 2 implementations and a lot of poor USB performance related to that got blamed on the standard itself and/or the devices being used. Many USB 2.0 chipsets out there have to scale themselves down in speed or go into a form of "compatibility mode" if there are also USB 1.1 devices connected This can greatly effect performance of connected devices as can just having multiple USB 2 devices connected, even if most devices are idle. Firewire has its own connectivity issues in that devices must by parallel linked or daisy-chained and bandwidth operates in a spill-over fashion. It's easy for the first device on the chain to hog all the bandwidth and subsequent devices are at the mercy of the device(s) ahead of them and how their interface and chipsets work. There are lots of compatibility issues out there between Firewire devices too and you'll find that many of them are single-ended anyway so they can't be stuck in the middle of a chain. There are Firewire hubs, but that's a whole other can of worms, but in a nutshell... They suck.

FWIW, I've thrown a few 7200rpm 250GB to 500GB drives in external enclosures from Vantec, CoolMax and a few others. For a drive that's fast enough to sustain 30MB/s or more, I've found that these enclosures usually do a pretty good job at allowing for that drive speed. But most HDDs out there can't do much better than this and I haven't tried any RAID enclosures other than drobo. All my external RAIDs connect as NAS, so I don't have any on the USB / FW interface.
 
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