Another hard drive topic

General Discussion
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I was pondering the hard drive requirements and the flag that jumped up in my head was that the requirements are very light compared to Mpeg based systems. A usb powered 5400 rpm drive would choke on such a system . But it also occurred to me that higher performing drives might still be a small advantage to tablo. With the motivation to support even some of the slow backup drives like passport and elements, which are designed for intermittent power saving use, im wondering if a desktop 7200 rpm drive wouldn’t give more reliable service.

Yes I see lots of success stories with the portables, and yes I’ve read most the “tested drives” thread, and I see tablos own recommendations for elements drives, but it seems one would be better off with a continuous duty cycle 7200 rpm drive, especially for supporting multiple streams has anyone studied this ?

1 Like
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Your question is really interesting, and probably deserving of some study. I’ve been mulling it over in my mind, and came to the conclusion that one might conceivably arrive at a theoretical answer taking into account the number of streams the Tablo can record, as well as the number of streams it can concurrently disperses to viewing clients.

Some practical limitations may manifest themselves in other device limits, such as the throughput limit of the USB2 port, the limit of steams transmitted over the WiFi transmitter, etc.

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Even a standard quality 5400RPM drive is going to be able to max out the USB2.0. transfer speed. But in this use case, thats still more than required…

The Highest quality setting available is 10Mbps.

The max simultaneous streams is rated to be 6. And a 4 tuner could in theory be recording 4 different things at the same time… Luckily this makes for some easy math with 10 video streams set at 10Mbps…

Now I am not sure if that 10 quality setting is strictly video but even if you factor in another 500K each for some insanely high quality audio, you are still only at 105Mbps.

While USB2.0 is rated at 480, we know thats not possible in the real world, 200 ~ 240 is more common, which is still DOUBLE what the max load would be for the Tablo, set at max quality with 6 streams of pre-recorded content and an additional 4 tuners recording 4 other streams.

So as far as data transfer any way you look at it 5400RPM and USB2.0 is plenty.

Now, there are 2 areas that (IMO) you might see some improvement with a higher speed / higher rated Hdd.

First, and where I think it makes the most compelling argument, is duty cycle ratings. While transfer speed is not an issue, you are correct that the standard portable Hdd is not typically rated for continual use, for this reason alone, I would second the argument that a desktop, continuous duty cycle drive SHOULD give you longer / more reliable use.

I also prefer the desktop Hdd because I prefer to not power it from the Tablo. It has been beaten to death that Tablo runs on the warm side (and we have seen a decent number of power supplies die), so while I have never believed mine was TOO hot, even when I had a USB powered drive, the idea of taking some load off the Tablo helps me sleep at night.

The second thought isn’t so much about sustained transfer speed but rather initial load time. It does take a few seconds for Tablo to first wake up, tune to a channel, spin up the Hdd and start encoding the stream for playback. So while 7200RPM is probably not needed for sustained use, does it spin up and start taking data faster?

In this area a few have tried solid state drives and reported an improvement. I have been tempted to try them too but the price is still a bit too high for the large capacity I would need and I worry the duty cycles of SDD isn’t where it needs to be for this type of use.

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Exactly! Access time and latencies I would think are more important than burst transfer rate. A big 5400 drive with a weak USB power supply will be slow to spin and slow to access. Minimally a desktop 5400 with its own power supply would probably be the best balance. I just have to wonder, given that not all usb drives work well, that this corner of the design is the most susceptible to marriage problems between drive and tablo, production variabilities and the like.

Your heat observation is spot on.

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I too would hesitate to load up the Tablo with a current-drawing accessory - be that a fan, antenna amplifier, or HDD.

I swear the room I have my Tablo feels a lot warmer than any other room in the house - objectively, I know that can’t be possible or attributable solely to the Tablo, but still…

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I ran a 2TB WD portable Hdd and a Winegard antenna pre-amp off my 4 tuner Tablo for about 18 months, never had a problem.

Still prefer it with a desktop Hdd and the Antenna pre-amp with their own PS for reasons stated before but it should be said, its just a personal preference, I really have no proof, it worked just fine for me the other way too.

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I’m thinking we’re dragging this off-topic, but I’m tempted to put a power meter on the Tablo and see just how much power it uses during peak recording/streaming times. That would allow for a more informed discussion of how much “spare” capacity the power supply and the USB ports have to support other units. I’d be surprised if both ports can support much more than about 5 Watt/port.

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Convinience is good but I see no reason to tax the tablo power supply when you have the option to avoid doing so. Heat is the enemy of electronics and, other factors equal, cooler means lasts longer

1 Like
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For a standard 2.0 USB port, I would think the maximum power per port wouldn’t exceed the USB 2.0 standard.

Isn’t that (5 x .100mA) x 5V = 2.5W

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There aren’t many hard drives that can operate on 2.5W, so I suspect the drive would exceed that by some degree. Of course, Tablo never said to connect a drive to the USB port that draws power from there - their recommendation is for a “desktop” type drive with a separate power supply. But the port is there and I’ll be betting that people use that - and if they exceed the power requirements that might explain some of the issues we see cropping up here.

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For what it is worth. I have been using a 2TB seagate portable passport usb drive thru a 4 tuner Tablo for 3.5 yrs. They are sitting on top of a $15 laptop cooler and barely warm. (I do believe heat can be a serious problem with Tablo) I have had a few problems over the early years, but with the help of the very competent and professional Tablo support personnel, all problems were solved in acceptable time. I did some major upgrading to my network equipment which has allowed me to run the last 2 yrs with very few problems. We are loving a Tablo and save over $100 mth every month!!! Cheers

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The tablotv site says:

“We recommend Western Digital Elements drives and Seagate Expansion drives, but most other brands/models are compatible”

I turned my WD Element drive over and over and still couldn’t find a power connector different from the actual USB cable.

2.5 drives usually require much less power then larger disks.

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Have a close look at your WD elements drive. Is that a USB 2.0 or USB 3.0 port on it? Depending on when you purchased your drive, it may be USB 2.0 or USB 3.0.

Now, regardless of what Tablo tells you or what they recommend, would you agree that USB 3.0 has a higher power specification than USB 2.0?

Would you agree that an unwary person making a decision today to purchase a USB 3.0 WD Elements drive could be attempting to power it through a USB 2.0 port on the Tablo and thus be out of spec?

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The USB 3.0, 3.1, 3.2 states:

“As with earlier versions of USB, USB 3.0 provides power at 5 volts
nominal. The available current for low-power (one unit load) SuperSpeed
devices is 150 mA, an increase from the 100 mA defined in USB 2.0. For
high-power SuperSpeed devices, the limit is six unit loads or 900 mA
(4.5 watts), almost twice USB 2.0’s 500 mA.”

But the cables for USB 3.0 can be backward compatible to 2.0. A manufacture can build a USB 3.0 drive that is NOT downward compatible with USB 2.0 if they want. But if they claim it’s compatible with USB 2.0 that means it’s compatible with the standard. And the standard includes max power.

And if search the WEB you might find actual screen captures of WD Element drives connected to USB 2.0 and their power measurements.

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Feel free to do your own WEB searches for screen captures.