How many tuners per PC/server?

[daveyboyc]

Hi

 

I'm looking to setup a recording system that will record many channels throught the day simultaneously.

 

As anyone got any experience using many tuners at once? I'm looking to install 1 dual dvb-t, 1 pinacle quad tuner, and 2 dual dvbs into 1 quad core server.

[Lars_MQ]

If you only want to record, you don't need a fast PC. Just lots of fast harddisks.

[daveyboyc]

So what do you reckon to a couple of .TB hard drives?

[Lars_MQ]

well it depends. If you record 10 SD channel with round about 0.5 MB/s you need for 24 hour about 0.5 TB hd space...Remeber those values are only rough estimations...

[daveyboyc]

Yeah I was thinking of using about 6TBs every week or every 5 days and then having the drives wiped and start over. Do you know if its possible to time something like that?

[steven627]

Firstly I'd recommend that you opt for just satellite cards as one card will allow you to simultaneously record all channels that are broadcast on the same transponder, e.g. BBC1,2, 3 & 4 and Channel 5 are all on the same transponder so can all be recorded simultaneously using a single card and feed. As I understand it DVB-T can not do this.

Secondly Lars_MQ is right you don't need a quad processor, but I would recommend a good chip-set and a motherboard that supports RAID, and preferably for more than just 2 HDD, note that while most motherboards have plenty of SATA connections the norm is that only 2 of these can be striped (RAID 0). And that's my most important recommendation, stripe as many disks as you can, this will give you a much faster throughput, e.g. a 2 disk stripe is roughly double the speed of a single disk, and so on.

With regards to automating disk clean up just create a .bat file with the DOS commands that will do the deleting that you want and set your task scheduler to run it whenever you want. If you are only going to use these disks for recording, i.e. OS and progs on another disk, then a quick re-format will ensure that they don't get fragmented.

[Griga]

e.g. BBC1,2, 3 & 4 and Channel 5 are all on the same transponder so can all be recorded simultaneously using a single card and feed. As I understand it DVB-T can not do this.

Recording channels simultaneously from the same transponder with a single DVB-T/C device is possible as well.

[bogdan1980]

I could only watch 1 channel and record another one on same transponder.

Not 2 live-tv recs on same transponder.

[Derrick]

I could only watch 1 channel and record another one on same transponder.

Not 2 live-tv recs on same transponder.

 

scrambled or fta?

[blasgl]

RAID is definetely overkill for many simultaneous recordings. Current 7200rpm SATA drives are fast enough.

[steven627]

Bogdan1980: I have recorded 9 channels simultaneously using a single satellite card.

 

blasgl: I obviously disagree with you. Nothing in life is definite (except death and taxes). It would really depend on a number of factors, like how many simultaneous recordings are being made, and what the bit-rate of each recorded channel is. There is also the added bonus that by striping a number of big disks together they will appear to the system as one big partition which will allow, more easily, many hours of recording without worrying about running out of space. Obviously there is the downside that if one disk fails you will lose everything, but I've been running a system with a 2 disk stripe for several years now and have not had any problems with it. That being said I have another system running on a single 750 Gb HDD and this has happily recorded multiple channels simultaneously, however the original poster said he wanted to record many channels, he doesn't actually specify how many nor which ones, continuously for a week so I would still hold with my original recommendation.

 

Derrick: FTA, scrambled may work differently and I'd be interested to know if it does.

 

Griga: Thank you for your input, I'd be interested to know if this is the case on the UK DVB-T system.

[blasgl]

@steven627: just an example... recording 20 HD channels simultaneously is going to write 30 Mb/s to the HDDs in relatively big chunks. Any modern 1 Tb HDD won´t be bothered to write at that rate. Of course you won´t be able to do much else with that disk but if that´s supposed to be a recording server, you won´t anyway, would you? And mind... 20 HD recordings at once!

[steven627]

basgl: I think I'd kind of agreed that multiple simultaneous recordings are perfectly possible on a single HDD, in fact I've just done it for 10 as a test. However, this doesn't negate the benefits, as I mentioned it gives you 1 big partition, I'm pretty sure that DVBViewer only records to the first given location so if your first drive runs out of space you'd have to manually re-set it to another. Furthermore, a media server will almost certainly have other things to do, e.g. supply clients with recorded programs. Lastly your example rates are not correct BBC HD runs a variable bit-rate going up to around 10 Mbits/s and ITV HD almost permanently runs at over 10 Mbits/s so 20 of those, I know there aren't 20 available yet, would run to over 200 Mbits/s.

[blasgl]

I´m not denying the possible benefits of RAID 0, I´m just saying it´s making things over-complicated where it´s not needed. It´s up to the first poster to decide which way to go.

 

DVBViewer and the recording server can record to multiple paths and change the target dynamically basing on available space.

 

My 30 Mb/s mean 30 Mbyte per second, not 30 Mbit per second. So 200 Mbit/s translates to 25 Mb/s

[Lars_MQ]

This does not sound like "personal" use anymore.

It might be possible the way you want it, but for this you have to contact Bernd Hackbart directly (-> http://DVBViewer.com...?page=impressum ) and talk to him about a fitting license for your purpose and the needed changes.

[steven627]

basgl: Fair enough, I did wonder as both recording rates and HDD data transfer rates are usually given in bits/s. I did notice that you'd put b and not bits so wasn't sure. And yes a modern SATA 7200 rpm HDD will handle around 70 Mb/s so it will easily manage your example.

I'm surprised by you saying that DVBViewer will change recording path dynamically because I have 2 recording PCs with each others recording DIR mapped and when the PC recording has run out of space it has never used the mapped drive. Maybe this only works on physical disks?

[blasgl]

look at

http://en.DVBViewer.tv/wiki/Options_Service_-_Recorder

[steven627]

Ah there you go, I've not been using recording services.

[steven627]

This may seem obvious but thought it might be worth mentioning; regardless of which type of disk setup chosen it is important to make sure that the HDDs are kept well cooled, particularly if there are a number of them and the system is running more or less all the time. In fact the whole system needs to have a good airflow if it is going to be reliable. I'd advise at least one outtake, ideally with a good intake on the same side but as far away from each other as possible, the intake does not have to be active, ie. have a fan, but if noise isn't an issue then it helps. Failing that running centrally from opposing sides. If necessary, an additional fan guiding flow across the HDDs. Also passive HDD cooling mounts are very effective, such as the Zalman ZM-2HC2, but they still need airflow.