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Old 09-20-2012, 11:33 AM   #61
L David Matheny
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Quote:
Originally Posted by jgantert View Post
WD just came out with a new 1TB Velociraptor drive. $302 on Amazon. 10000 rpm, 5yr warranty. That would probably speed up the Tivo nicely, if it could dissipate the heat enough.
I doubt that a 10000-rpm drive would speed up a TiVo in any way that would answer the complaints of sluggishness. And yes, heat and current draw could very well be a problem.
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Old 09-20-2012, 09:38 PM   #62
mattack
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Yeah, you can buy as slow as a drive as you can get nowadays, and it's fast enough for a Tivo.
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Old 09-21-2012, 07:28 PM   #63
jgantert
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Quote:
Originally Posted by mattack View Post
Yeah, you can buy as slow as a drive as you can get nowadays, and it's fast enough for a Tivo.
Maybe, but wasn't the OPs claim that the SSDs extra speed made the Tivo faster? So shouldn't that apply to the faster 10000 rpm drives as well (although not as much of a speed up)?

BTW, I'm not seriously considering a 1TB Velociraptor drive, just discussing.
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Old 09-22-2012, 02:08 AM   #64
lrhorer
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Quote:
Originally Posted by ccfoodog View Post
It was mentioned that much of the media storage IO is undesirable to have on an SSD. I just wanted to point out that swap is in the same category.

In reality, the better option is to eliminate swap. It is fine to run Linux systems (and modern Windows variants for that matter) w/o swap. The trick is you just need enough RAM to not need swap.
I would not say it is "fine" to eliminate swap. If the kernel runs out of memory and there is no swap, the system crashes. While often one may essentially insure there is more than plenty of memory, things can happen that suddenly and unexpectedly cause the need for memory to soar. I know, I've had it happen on Linux systems on several occasions. In the case of the TiVo, a GSOD will cause the TiVo to write out all its memory into swap space and then attempt to repair the problem. If there is not enough swap space (like zero - swapping turned off), then the TiVo will enter into an infinite reboot loop.

Besides, the TiVo does not implement very much swap space - only 128M on S3 TiVos, nor does it use it much:

Code:
System Information Kernel Information

Version 2.4.20
Compile #1 Thu May 6 18:03:53 PDT 2010

Memory Information

Memory Statistics:
        total:    used:    free:  shared: buffers:  cached:
Mem:  130539520 94642176 35897344        0 11698176 51814400
Swap: 133881856 15560704 118321152
MemTotal:       127480 kB
MemFree:         35056 kB
MemShared:           0 kB
Buffers:         11424 kB
Cached:          48852 kB
SwapCached:       1748 kB
PriActive            0 kB
Active:          46832 kB
Inactive:        22796 kB
HighTotal:           0 kB
HighFree:            0 kB
LowTotal:       127480 kB
LowFree:         35056 kB
SwapTotal:      130744 kB
SwapFree:       115548 kB

File System/Disk Information

Filesystem    Type    Size  Used  Avail  Capacity Mounted on
/dev/hda7     ext2    248M  145M    90M     62%   /
/dev/hda9     ext2    248M   28M   207M     12%   /var
/dev/hda2     ext2    248M   79M   156M     34%   /var/hack
11M is just not a lot of swap.

Quote:
Originally Posted by ccfoodog View Post
Is it not possible to increase the RAM on these devices?
With a soldering iron, perhaps, but it won't gain the user very much, at all.

Quote:
Originally Posted by ccfoodog View Post
What are the HW specs for the HD and Premier? How much swap is allocated?
That is a TiVo HD shown above. The Premier may have increased swap space some, but I expect not much. The RAM has been increased to 512M.

Quote:
Originally Posted by ccfoodog View Post
If you can add the amount of RAM that they allocate for swap and remove the swap entry in the fstab, you should be golden.

Memory is so cheap these days it would be a shame if it was not possible to run w/o swap due to memory restrictions.
Not so much, really. As you can see above, 27% of real memory is still free, and this TiVo is running quite a few more applications in memory than a stock TiVo, including ftpd, TivoWebPlus, tserver, and ntp.

The biggest boost to responsiveness would come from caching the guide database, which is kept in the MFS file system, and can be up to 512M in size; considerably larger than the memory on the S3 / THD. Simply adding memoryto the motherboard won't automatically cache the database, however.

Last edited by lrhorer : 09-22-2012 at 02:39 AM.
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Old 09-22-2012, 02:36 AM   #65
lrhorer
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Quote:
Originally Posted by jgantert View Post
Maybe, but wasn't the OPs claim that the SSDs extra speed made the Tivo faster? So shouldn't that apply to the faster 10000 rpm drives as well (although not as much of a speed up)?

BTW, I'm not seriously considering a 1TB Velociraptor drive, just discussing.
Not really, no. Some,yes, but not that much to make it worth writing home. First of all, even replacing the hard drive with an SSD does not have anything like an astounding effect. It's noticeable, but not incredible. Remember, the UI and crunching guide data are low priority processes, and much of the rest of what the TiVo has to do are real-time priority. It's very easy for the TiVo to be too busy to take much time to update the UI and guide calculation processes, no matter how fast the guide data can be shoveled into memory. Secondly, compared to the speed of even a rather slow SATA drive and one with only 8M of cache, the guide database is still somewhat small. Finally, the big advantage, such as it is, for the TiVo with an SSD drive is its tiny seek times. Seeks for an SSD can be 1/20 as long a 5400 RPM drive, while a 10K drive is only about twice as fast.
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Old 09-23-2012, 02:11 AM   #66
Worf
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The main reason why an SSD is faster in general use is because the seek times are two orders of magnitude or more faster. A hard drive typically takes 7-8ms to do one seek, which limits you to around 150-odd I/O requests a second. The smaller the read or write, the lower the throughput. A SSD can do a seek in well under 100us which increases the I/O rate to 1000+, though even the slowest ones tend to go above 10,000.

For a computer that's reading and writing a bunch of small blocks (page file, little files and seeking), this jump is significant and makes the system snappier.

For TiVo, it's a bit more mixed - TiVo prioritizes video capture and playback, which involve long big reads on the hard drive (roughly 1MB sized chunks, roughly a second of video)=). The UI and other tasks are low-priority, so when they need to read or write the drive, their accesses are scheduled in-between. Of course, these things read lots of little chunks off the drive, so the head has to go flying around, and TiVo needs to schedule the video I/O first. So the UI and stuff slows down because the drive can only do so many accesses in-between video accesses.

The SSD helps because it really doesn't matter - the video I/O is completed quickly, and the rest of the UI I/O is pretty damn quick as well so it can be snappier as the random user I/O can be completed way faster so there's less waits in-between video I/O.

And no, even the the 10K drive cannot seek much faster - even the fastest drive that could do would probably take 5ms seek times, which limit you to 200 I/O a sec. Vs. 10,000+ for an SSD.

A TiVo would be an ideal situation though for a hybrid drive. If the drive is smart, it would cache all the user I/O in the mini-SSD, while the big I/O reads and writes remain uncached. (Given the reads and writes are to contiguous sectors, the algorithms should be smart enough to realize this as 1M chunk size is basically media speed - do this and you'll achieve the fastest reads and writes off the drive).

Windows checks for SSDs by doing a speed test - random 4K reads and writes. It then uses I think 20MB/sec throughput. A 5ms seek drive (200 I/O a second) doing 4K reads only gets you ... 800K/sec. 10,000 I/O per sec at 4K is 40,000K, or 40MB. To make 20MB, you would have a 5000 IOPS drive, which for an SSD is pretty slow (you're looking at "fake" SSDs using SD cards and CompactFlash cards to reach this class).

RPM speed is mostly meaningless as the total access time is dominated by the head seeking, rather than the waiting for the sector to pass below it. Nonetheless, they are great if you're wanting maximum throughput continually, like say, video editing. Here it's long big reads with little seeking where the benefit of an SSD is very minimal.
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Old 09-23-2012, 01:13 PM   #67
DougJohnson
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Quote:
Originally Posted by Worf View Post
RPM speed is mostly meaningless as the total access time is dominated by the head seeking, rather than the waiting for the sector to pass below it.
I think this understates the importance of rotational latency. A 10,000 rpm drive is going to have an average latency of 3ms. That is a pretty significant addition to a 5ms seek time. -- Doug
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Old 11-11-2012, 08:30 PM   #68
ciper
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Just stumbled across this thread.
I've been using various models of the Momentus XT in multiple PCs with great results. I had an extra 750gb unit and planned to use it in my Tivo but cannot get it to boot.

I made a thread here http://www.tivocommunity.com/tivo-vb...d.php?t=495978

Basically it shows the "Welcome! Powering up..." screen for a moment and then goes to solid grey, never to move again.

I can't figure out why it wont work since the drive appears to the OS as a standard 750gb Sata drive.
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