# Can you daisy-chain the SATA drives for Series 3?



## Bierboy (Jun 12, 2004)

I'm not too swift when it comes to this stuff, so someone smarter than me, please help out. Would you be able to daisy-chain several SATA drives to increase the capacity of the Series 3 beyond its internal and one external SATA drive?


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## petew (Jul 31, 2003)

The eSATA spec allows for the external device being an array of disks.


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## Justin Thyme (Mar 29, 2005)

Silicon Image has a Sata "Drive" that does what pete was talking about and goes up to 2 Terabytes. If you want to build your own, they will sell to OEMs a chip to handle the port addressing for up to 5 drives in a box. SiI 4726. With current 5 GB drives max capacity using this chip would be 2.5TB. Since I have about 1300 DivX SD shows on 1TB (mostly movies), this would translate to roughly 3200 shows. Whoohoooooo. Let's see- using today's best prices on 300GBs, you could have a 2000 movie collection for 5X$80 or $400 plus the eSata enclosure- maybe $100. Not a bad VOD set up. Tough break Cablecos, and iTms. "Best laid plans of mice and men" and all that.

The 2 TB drive  I think I mentioned earlier. DT_DC mentioned this company long ago when discussing the latest Moto 6412's support for eSata's.

But remember Mega's admonition- this is not like an external USB- The same mating between system and drive occurs and you will get teh same results as if you try to swap a drive from one Tivo to another. No go.


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## Bierboy (Jun 12, 2004)

Justin Thyme said:


> ...But remember Mega's admonition- this is not like an external USB- The same mating between system and drive occurs and you will get teh same results as if you try to swap a drive from one Tivo to another. No go.


I've got that...once hooked up, you're basically done. I'd just like to maximixe storage on the Series 3.


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## Gregor (Feb 18, 2002)

Justin Thyme said:


> Silicon Image has a Sata "Drive" that does what pete was talking about and goes up to 2 Terabytes. If you want to build your own, they will sell to OEMs a chip to handle the port addressing for up to 5 drives in a box. SiI 4726. With current 5 GB drives max capacity using this chip would be 2.5TB. Since I have about 1300 DivX SD shows on 1TB (mostly movies), this would translate to roughly 3200 shows. Whoohoooooo. Let's see- using today's best prices on 300GBs, you could have a 2000 movie collection for 5X$80 or $400 plus the eSata enclosure- maybe $100. Not a bad VOD set up. Tough break Cablecos, and iTms. "Best laid plans of mice and men" and all that.
> 
> The 2 TB drive  I think I mentioned earlier. DT_DC mentioned this company long ago when discussing the latest Moto 6412's support for eSata's.
> 
> But remember Mega's admonition- this is not like an external USB- The same mating between system and drive occurs and you will get teh same results as if you try to swap a drive from one Tivo to another. No go.


Any pricing on that puppy?


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## dmdeane (Apr 17, 2000)

What would be cool is if some third party, or TiVo, made an expansion box that could hold multiple hard drives, and would look like just another set top box that you could put on top of the Series 3 box and connect to it through the SATA port. 

That way you could have the multiple hard drives set up properly to use the single SATA port, without the consumer having to worry about the technical details like daisy chaining (or RAID), etc., ie, make it invisible from the consumer's perspective. Plus, the resulting box would look nicer than the sort of "tacked on" look of the free standing external box shown at CES 2006. Ie, make it just another AV rack box.

Make the hard drive expansion box the same size, shape, and color of the Series 3 box. Have consumer buy the expansion box. Put it on top of the Series 3 box, in the consumer's AV rack. Plug it into the Series 3 box. Done.


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## megazone (Mar 3, 2002)

TiVo told me the box would not support daisy-chained drives or SATA RAID arrays, at least not out the door.


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## dmdeane (Apr 17, 2000)

megazone said:


> TiVo told me the box would not support daisy-chained drives or SATA RAID arrays, at least not out the door.


Is there a technical reason for this that us non-techies could understand? Is it fixable in some future software or firmware update?


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## 1283 (Sep 8, 2000)

Gregor said:


> Any pricing on that puppy?


http://www.lacie.com/products/product.htm?pid=10458


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## 1283 (Sep 8, 2000)

megazone said:


> TiVo told me the box would not support daisy-chained drives or SATA RAID arrays, at least not out the door.


These boxes support RAID in hardware, so TiVo would only see a large virtual drive.


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## megazone (Mar 3, 2002)

c3 said:


> These boxes support RAID in hardware, so TiVo would only see a large virtual drive.


As long as it looks like a single drive, that may work.

As for reasons - I think it is just development time and effort vs the return. I doubt a large percentage of users is going to be looking for terrabyte storage. Especially with TiVoToGo and such allowing offloading to a PC fileserver with unlimited storage, which is what I'd be more likely to do.


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## parzec (Jun 21, 2002)

I wonder what would happen if you connect a drive, record some shows, then later disconnect it. Would you run into the same problems as the meshed drives on the series 2? Seems like if it is treated as one big virtual drve you would...


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## VinceA (May 13, 2002)

I would think that wouldn't happen. I'm hoping they don't interleave the storage. Since it's external TiVo would probably account for things like accidental removal, etc.


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## smak (Feb 11, 2000)

How are the shows on the external drive going to be displayed? Just as part of the now playing normally, like a second internal drive would be, or like your PC or second Tivo in the other room shows up now, at the bottom of now playing?

It'll be interesting how they implement it.

-smak-


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## 1283 (Sep 8, 2000)

VinceA said:


> I would think that wouldn't happen. I'm hoping they don't interleave the storage. Since it's external TiVo would probably account for things like accidental removal, etc.


My guess is: record on internal drive and then copy it to external drive, similar to MRV.


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## Justin Thyme (Mar 29, 2005)

Gregor said:


> Any pricing on that puppy?


Sorry Gregor- missed your question during the CES flurry. These are designed for the businesses that typically pay multiple dollars per GB rather than 25 cents per gigabyte. That's why I think roll your own using an enclosure or a hobby project using the SiI 4726 chip will be the way S3 owners will typically go. I'm have a similar opinion as Mega though- unless the T3 network performance is pretty awful- I don't want the box in the living room- leave that stuff on the Tivo server.

Anyway, the SV2000 unit that has a capacity for 5 internal SATAs was selling last summer at a street price of $2200 configured with drives for 800GB. If this is still the only show in town and I had to do SATA, I'd buy the cheapest one I could find, then slap big drives in. If it didn't autorecognize them, put the old drives back in, and return the unit.


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## Dennis Wilkinson (Sep 24, 2001)

Megazone posted some related info (http://www.tivolovers.com/252572.html) a while ago:



megazone said:


> Oh, one other tech detail I forgot. The S3 is still using IDE drives internally, only the external drive is SATA. Also, the external drive is not removable in the conventional sense. Once it is connected, the OS makes it part of the file system and shows may be recorded using both the internal and external drive - as in the SAME show may have its bits scattered on both. If you disconnect the external drive the unit will cope with it, but any shows recorded with any data on the external drive will vanish. So it isn't something you connect, record to, then take to another unit to watch the shows.


In other words, it's like an internal upgrade drive today, except that you can "divorce" the drive at will, so long as you don't mind any show that partially spans that drive completely.


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## Gregor (Feb 18, 2002)

Thanks for the pricing info folks! The roll your own method looks great as long as someone else engineers the interface card, it's way beyond my skillset.


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## morac (Mar 14, 2003)

Dennis Wilkinson said:


> Megazone posted some related info (http://www.tivolovers.com/252572.html) a while ago:
> 
> In other words, it's like an internal upgrade drive today, except that you can "divorce" the drive at will, so long as you don't mind any show that partially spans that drive completely.


I do hope there is an indicator as to which shows are stored either totally or partially on the external drive. That way the user knows which shows to back up via TTG. Otherwise the user would have to do a complete backup and restore. Though if they've optimized TTG speeds that might not be terrible.


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## megazone (Mar 3, 2002)

I think the point is, there shouldn't be a reason to unplug the drive in normal operation.

One thing I didn't think to ask is if you disconnect the drive and then reconnect it, do the shows come back? I know you cannot take it to a new box and connect it and have the shows there. But I would like to think reconnecting it to the same box would work.


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## Justin Thyme (Mar 29, 2005)

Calculating storage capacities/ xfer rates.

The numbers that TivoPony are using are:
300 SD Hours or 30 HD hours on 250GB Hard drive.

That figures to about 833 megs per hour for SD, or 8.3GB/hr for HD.

Requiring 1.8 Mbits for xfer of SD, and 18.4 Mbits for HD.

(The surprizing thing about these figures for cable is the difference in SD versus HD resolution is 4x, but the storage requirements here are 10x. I know the cable companies transmit "SD" shows at 480x480, so less than SD quality, but this difference wouldn't account for the 10x difference.)

There was one other interesting interchange in the video and I wonder if anyone also picked up on it. They were asking- So do I have to buy the Tivo Sata? Well can I buy any old drive and make it work (TivoPony-no, it needs the Tivo File System) Officially we're going to have to buy it from Tivo but if we "bless" a third party drive??? Not going to go there? TivoPony-No...Q:Alright. TivoPony wouldn't comment.

Well, no comment from TivoPony, and that is what he'd probably say in response to my question, which would have been-

Will the Tivo File system support 64MB blocks?
Or more directly, what is the file system limit for the Sata External drive capacity?​
Anyway, if blocksize is up to 64MB, then it means that a JBOD** enclosure capacity theoretically could be 4TB. (Current limit for a volume is 64M blocks each of size 16MByte using the -r4 switch, so 1 TB)

My wild ass guess is that we'll be able to rig these things up pretty easily for 1TB. - a lot easier than the Tivo HD hard drive procedure- and format them properly.

**Just a Bunch of Disks - simple arrary as opposed to a RAID0/Raid5 configuration.


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## Dennis Wilkinson (Sep 24, 2001)

Justin Thyme said:


> (The surprizing thing about these figures for cable is the difference in SD versus HD resolution is 4x, but the storage requirements here are 10x. I know the cable companies transmit "SD" shows at 480x480, so less than SD quality, but this difference wouldn't account for the 10x difference.)


Using your 480x480 SD number, that's 230,400 pixels for SD. 1080i is 1920x1080, that's 2,073,600 pixels for HD. That's a 9x increase in resolution, not 4x (Full-res SD is 345,600 pixels, so 1080i is about a 6x increase.) But resolution doesn't matter as much as bitrate. Remember that the peak DVD (which is SD) bitrate is only slightly less than half the peak HD bitrate, not 1/6th.

Also remember that the 300 hours capacity is at TiVo Basic quality, presumably as recorded today, which is compressed even more heavily than most digital cable.

The rule of thumb for digital cable is usually that a single analog channel's bandwidth (6Mhz band) using QAM256 modulation can carry up to 6 SD channels at peak bitrates or 2 HD channels at peak bitrates, although that oversimplifies a little. You could expect disk usage to compare the same way.


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## 1283 (Sep 8, 2000)

Justin Thyme said:


> **Just a Bunch of Disks - simple arrary as opposed to a RAID0/Raid5 configuration.


I'm not sure TiVo wants to deal with multiple devices in a JBOD configuration, although a JBOD-only enclosure may be less expensive.


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## Justin Thyme (Mar 29, 2005)

c3 said:


> I'm not sure TiVo wants to deal with multiple devices in a JBOD configuration, although a JBOD-only enclosure may be less expensive.


The Silicon Image SiI 4726 makes it look like one physical device to the SATA host. The chip costs about $24 in quantities of 5K, so cheap jbob enclosures could be churned out for not too awfully much.

The key question is MFS's capacity limitations. Still- with current capacities, 1TB internal and say 600GB drives by the time the S3 comes out- 1.6 TB is not a shabby amount of storage for a super high end home theater. 4TB sounds so much nicer though- and geez- if it were loaded up with divx shows like mine, that's over 4000 movies at SD resolution.

Dennis- Yeah ok that's right factor of 6- but minor nit-480i is 640x480, so the resolution SD figure should be 307200, right?

I remember now where 4x came from. It has no bearing but I remember that when local broadcasters go all digital may have 1 HD channel or 4 SD channels.


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## 1283 (Sep 8, 2000)

Justin Thyme said:


> The Silicon Image SiI 4726 makes it look like one physical device to the SATA host. The chip costs about $24 in quantities of 5K, so cheap jbob enclosures could be churned out for not too awfully much.


3726 is JBOD only and costs about half as much.


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## Dennis Wilkinson (Sep 24, 2001)

Justin Thyme said:


> Dennis- Yeah ok that's right factor of 6- but minor nit-480i is 640x480, so the resolution SD figure should be 307200, right?


That wikipedia entry is wrong. ITU Recommendation 601 (which is what the video editing space uses to define SD resolutions), the DVD spec, and the ATSC spec all use 720x480 or 704x480 as the primary NTSC-equivalent SD resolution (720x576 in the PAL-equivalent world.) The pixels aren't square in those cases, either. Other flavors (most notably 320x480) are also called out. Yes, yes, the ATSC "Table 3" calls out a square-pixel flavor as well, but no one uses it, since it doesn't correspond to any studio standard or commonly-used interface (which, for SD, are nearly all ITU. Rec 601).

The resolutions that that wikipedia entry uses, 640x480 for NTSC and 768x576 for PAL, are the square-pixel equivalents, and are atypical for storage.


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## Justin Thyme (Mar 29, 2005)

You want to fix the entry or shall I?


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## Justin Thyme (Mar 29, 2005)

c3 said:


> 3726 is JBOD only and costs about half as much.


Hey- great point. Sorry- I was working off their announcement at CES2006 of the newer chip. Yeah- this has been around longer- so their are existing modules for a rolll your own solution. This is great. No doubt Weaknees and PTVupgrade will be providing these for people who don't want to get their hands dirty. Besides assembling, they would "Bless" them- that is formatt them with MFS and whatever else Tivo puts on them so they are recognized properly. 








Yay! Maybe ready for roll your own Cheap Tivo Sata?​Hey are you an MFS gearhead? You know the answer? -r4 is the maximum block size setting right- Tivo File system won't recognize 64M yet, right? I don't get what is magic about 24bits of address space into a block. If it were 32 or 31, I'd get it. but 24?

Anyhow, that module is $99 at one outfit and is also available at CoolDrives. Most of the enclosures I saw at Cooldrives were not port multiplers- eg 4 drives, they had 4 sata connectors on the back. I saw one apparently using this module, but wow. $439. For a box, the power supply the module and fans? Wow- better to grab a dead PC, gut it and stick the module in. I don't need hot swap- besides it probably would freak the Tivo.


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## Justin Thyme (Mar 29, 2005)

Hey TivoPony, uh I know you guys got uhhhh a few things on your mind, but just a thought here- maybe it would be nice if a system setting could be- power saving mode, and the Tivo could send a signal to the Sata to sleep itself. I don't know if the eSata protocol supports this, but it would be neat if these puppies wouldn't have to be spinning 24/7. I'm guessing you'll model it to the user as a folder, and what I'm saying is that when they open the folder, if you had the power save switch on, the first entry would request entry and there would be a pretty huge delay. But after that, it would keep spinning for a while - like 15 minutes or whatever so that peeking again wouldn't take so much time.

That's the main thing I have seen with my huge TivoServer. It's disks are spinning all the time and maybe once or twice a day, there might be some IO to a Tivo. 

It's a green thing. If it doesn't take more than 10 minutes of an engineers time, then maybe in first release- otherwise something maybe to have at the back of folks' mind for the future so they don't paint themselves into a corner so they can't do the feature later.

I'm telling you that if 300GB drives are $79 on special now, by next half of year, 1.5TB satas are easily going to be like $500 roll your own. 

Of course with 1800 hours of SD recordings, it will be nasty finding stuff. The navigation becomes pretty important. A guide interface to recorded content (search by actor, director, keyword) would be just dandy for me. 

Woooo Hooo. This is going to be soooo infrickingcredible. It really does take the TV mind shift to a new level when you can see an awesome movie on a whim, and see it at the cool scene just where you left it a month ago.


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## 1283 (Sep 8, 2000)

Justin Thyme said:


> If it doesn't take more than 10 minutes of an engineers time.....


Putting a drive in standby mode is a standard ATA/SATA command, but supporting the sleep mode implies that a wakeup procedure also has to be implemented. Nothing just takes 10 minutes.


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## Justin Thyme (Mar 29, 2005)

Well, yeah. And I have spent many a sleepless night coding stuff to meet a ridiculous time estimate I made.

But it doesn't hurt to make things known to engineers otherwise, you pass up a lot of low hanging fruit. Eg I was having lunch with the lead from another product group that was using some code my team was responsible for and he mentioned a feature they were working on and I asked him if my module did x rather than y would it help and he almost fell out of his chair.

It really was only two lines of code and had no side affects. We just implemented it a certain way based on false assumptions about how other folks would use it. And he never asked because he had much higher priorities and thought this fix was a big deal.

Talking is good sometimes. A lot of very cool stuff happens due to hallway conversations.


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## mattack (Apr 9, 2001)

megazone said:


> I think the point is, there shouldn't be a reason to unplug the drive in normal operation.


I understand that, and see why it was designed that way.. But I geekily would like 'removable storage', even if it's entire hard drives! Fill one up, put another drive on.
(I'd really want to put seasons of a particular show on a hard drive..)

I realize that's not something most people would want to do.


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