New user moving from Windows Media Centre (1 Viewer)

[HTPCSourcer]

More than enough. You can pause Live HDTV for more than one hour or SDTV for more than two hours before you are running out of space.

Hhm, this will depend on the number of concurrent tuners and streams that you have. The statement is certainly correct for one stream, however, the architecture of MP(1) is such that you have to define a fixed quota of RAM for each tuner. It's not managed dynamically. In a, say, 4 tuner environment your 4 GB of RAM will suddenly offer only 1 GB, which is equivalent of approx. 15 min of HD only.

 

[Lehmden]

It's not managed dynamically In a say 4 tuner environment

I'm not sure about the space not managed dynamically. If it really is so its a huge drawback imho and definitely needs to be fixed, enhanched in TVE3.5...

Nevertheless you have one hour HDTV on such a RAM Disk Four times 15 minutes is one hour total. And even this 15 minutes are way enough to answer a phone call or go to the toilet. If you know it will be a longer break, the recording option is the one to choose, not pause...

 

[mm1352000]

Timeshift files are created as and when needed.
General approach is to create 1 file (size configurable) at a time until [min files] are used. Then files will be recycled until/unless TV is paused. At that time TV Server will use up to [max files].

 

[HTPCSourcer]

Hi mm,

I am not sure if I understand. Reading the above I conlcude that it is dynamic. Hence the max settings can be chosen such that the total usage equals the dedicated RamDisk space (minus overhead). Assuming that the maximum filespace is used, another stream coming up would then start to "eat" files away from the initial total.

Let's take an example: min = 3, max = 12, file size = 512K (or ca. 6 GB of RamDisk, ignoring overhead here)

• User1 starts watching a show: timeshifting files are written until all 12 files are used, then cycling begins
• User2 starts watching another show from a different client: timeshifting files get written and the number of allocated files for user 1 is reduced
• User3 and User4 start watching different channels: at some point we will have 4x 3 timeshift files for the four streams.

What happens when a fifth user joins the party?

 

[Lehmden]

User1 starts watching a show: timeshifting files are written until all 12 files are used, then cycling begins

Not as I understand this. 12 is the max number that only is used if you pause TV. Normally Timeshift files are written until min number (3) is reached. So the fifrth "party guest" is the first that lowers the amount of files everyone has available. As during normal operation you only need one or maximum two files, you can watch livetv from at least 6 clients at the same time. I would like to see a HDD, that is capable of reading and writing 6 HDTV streams at the same time without stutter... And so much clients most likely are not usable at the same time due to network ad/or server load at all, no matter how big the timeshift drive is.....

 

[HTPCSourcer]

Hi lehmden,

You very certainly correct. I am simply trying to understand the mechanics. So we would need to look at four users with four streams, all being paused at the same time, before evaluating what happens when a fifth comes along. Pretty theoretical, for sure.

I guess the lesson for me is that the max file number x size should match the planned RamDisk allocation.

 

[mm1352000]

User1 starts watching a show: timeshifting files are written until all 12 files are used, then cycling begins

As Lehmden said, the 12 files would not be used unless user 1 paused TV for long enough that files 4 - 12 were needed. Normally only 3 files would be used before cycling begins.

User2 starts watching another show from a different client: timeshifting files get written and the number of allocated files for user 1 is reduced

The settings are independent for each user user. In other words, if you set min = 3, max = 12, size = 512 MB then TV Server will use up to 6 GB per user.
If user 1 had used all 12 files (ie. no space left) then user 2 would not be able to start timeshifting. There is no concept of reducing allocation.

User3 and User4 start watching different channels: at some point we will have 4x 3 timeshift files for the four streams.

Yes, if you have 4 users timeshifting with the previously mentioned 3/12/512 settings then normally 3 files x 512 MB per file x 4 users would be the space used.

What happens when a fifth user joins the party?

User 5 would not be able to join the party. For a 6 GB RAMdisk there would be no space left to create a new timeshifting file, so timeshifting would fail.

So the fifrth "party guest" is the first that lowers the amount of files everyone has available.

Yes, that's right... assuming nobody else has paused (using more than 3 files) and that user 5 is even able to start timeshifting (space must be available to create at least 1 timeshifting file).

I would like to see a HDD, that is capable of reading and writing 6 HDTV streams at the same time without stutter... And so much clients most likely are not usable at the same time due to network ad/or server load at all, no matter how big the timeshift drive is.....

HD ~= 10 Mb/s = 1.25 MB/s
6 users x 1.25 MB/s = 7.5 MB/s x 2 for read/write = 15 MB/s
I would have thought that HDDs could handle that.

...and for the network, 7.5 MB/s = 60 Mb/s. A decent wired network connection should be able to handle that.

 

[Lehmden]

Hi.

6 users x 1.25 MB/s = 7.5 MB/s x 2 for read/write = 15 MB/s

Did you ever try to copy six (pretty big) files from one drive to another at the same time? If you copy one file it may have 100Mbyte/s (as example, could be more or less, depending on drive type, but 100MB/s is a good average value) , if you copy two files each has a maximum speed of 30 MB/s, if you copy three there is far less than 10MB/s and when there are four, the average speed goes down to some hundred KB/s. Not to mention the clearing of cache, what leads all other copy operations to stall completely for a certain time...And the copy operation only did read, not write... Timeshifting is comparable to copy a file to a different folder on the same physical drive. And here the speed is much slower than to copy from one HDD to a different HDD, so for 6 x timeshift at the same time you can expect a "speed" of a few kb/s only...
I often do copying of big files and I always avoid copying two files at the same time, as it's slow as hell compared to copy them one after another.

 

[mm1352000]

Did you ever try to copy six (pretty big) files from one drive to another at the same time?

Yes of course. The effect you're talking about is due to increasing random access (compared to mostly sequential access for one file). With the greatest respect, I think you're exaggerating a little. I just did a test simultaneously copying 6 large files (~1 GB) from one folder to another folder on the same HDD (Seagate 2 TB 7200 RPM with approximately 1.5 TB free - nothing special). Minimum copy speed for each file was approximately 6.5 MB/s. Remember that each HD stream is approximately 1.25 MB/s. It would seem there's more than enough bandwidth...

 

[HTPCSourcer]

mm,

Let me verify my understandig of the timeshifting logic based on what you wrote above. If User1 is pausing LiveTV long enough, all max files will eventually be used. User2, if not already connected, would then not be able to use LiveTV, or, if already connected, unable to pause LiveTV.
.