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I'm putting together an HTPC with a dual tuner card. If I wanted to play a video from the hard drive while the card records live TV, will 1 hard drive be able to handle the simultaneous reads and writes, or should I have two hard drives so that one will handle the recording while the other does the playback?
 

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One drive is more than adequate for recording multiple streams while playing back to several clients. Best performance will be obtained if you put your OS and apps on a separate, small hard drive and have a large drive for your data (recordings, etc).


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Quote:
Originally Posted by Bigbird999 /forum/post/16966569


One drive is more than adequate for recording multiple streams while playing back to several clients. Best performance will be obtained if you put your OS and apps on a separate, small hard drive and have a large drive for your data (recordings, etc).BB
Quote:
Originally Posted by LonZa /forum/post/16966650


Cool thanks. I'll start with 1 hard drive and see how things work out.

I agree with Bigbird. I would put the OS on its own small drive. Find a good deal on an 80GB-500GB. And I'm kicking myself for not going IDE for DVD and OS drives to have more of the SATA connectors for TB drives for recordings.

Good luck.
 

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I have actually done 4 concurrent ATSC recordings to one hard drive without issue.


You WILL want the TV to record to a separate drive from your OS, though. Otherwise, if a virus scan or defrag occurs while recording, the recording will suffer.


As for an OS drive, SPEED is the primary concern...and by SPEED I mean access time (sustained transfer rate is really unimportant). The larger hard drives do well here as they have high data density...but you have to keep them relatively empty or the drive arm will have to go everywhere making access time suffer.


Or, you can get a drive with a very fast fast access time (both seek time and rotational latency make up access time). WD Raptors and SSDs (preferabley Intel or Indilinx based) will do extremely well here. I currently use a 150GB WD Raptor, but I try to keep only about ~35GB on it at any one time. I will be buying an Intel 80GB SSD as soon as the 2nd generation drives are available.


Also, the more drives you have means the more pieces of hardware can read/write data concurrently! I'm a little overkill with 5 (1 OS, 1 Programs, 3 TV/Storage) but I think at least 2 is a good idea. RAID is too much to mess with IMO...I do weekly imagings of my OS and APP drive to an external once a week. Also, RAID will do nothing if it is a user error or virus.
 

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I've got an HTPC with six ATSC tuners. I have been able to record six shows simultaneously with no issues. Consider that an SATA II drive can transfer data at 300mbps and an ATSC broadcast has a maximum bitrate of about 19.5mbps, there's plenty of headroom left for even more tuners. In fact, I could theoretically get away with an SATA I drive/SATA controller at a maximum bitrate of 150mbps.


The only caveat is that the drive is writing to six different locations on the drive instead of a steady transfer to one contiguous location, which will obviously affect the overall performance and transfer of data. The good news is that most current SATA II drives can handle this with ease. That being said, a dual tuner setup is a cakewalk and poses absolutely no problems for your hard drive. +1 on the recommendation for keeping your OS and recorded programs separate. I actually have dual 1TB drives in my HTPC. One drive is partitioned for the OS and miscellaneous programs and has a separate partition for recordings. The 2nd drive is dedicated for recordings only. The way I understand it, when I'm using my PVR app (BeyondTV), the app is loaded into memory so it doesn't have to access the hard drive while it's running. The only hard drive activity involved is when a show is being recorded to the drive.
 

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I use 2 HDDs: 500gb laptop for OS, apps and 1tb for video files, HDTV recordings.


I have 2 dual tuners so that I can record 4 shows at once if needed. I was recording a show yesterday and I was going to try to run a movie from the hard drive at the same time to see what would happen. But I opted to just run a disc in the BR drive instead.


I think I'll try what you guys are talking about today or tomorrow.
 

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Just to repeat what others have said, I can record 5 ATSC channels while playing back at least 2 already recorded shows (don't know if I've ever done 5 recordings while watching 3.)


All from a single Seagate SATAII drive. 300GB in size I believe.


I do have the OS on a different physical drive. Also, I have the block size set for the max size (64kb if memory serves) this helps a lot according to others.


-Suntan
 

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Video file sizes

HD TV recordings ~ 3 MB/sec

BlueRay ~ 8 MB/sec max

SD TV recording ~0.5 MB/sec


Sustained, real world file transfer rates via different HDD interfacesare:


IDE ~ 40 MB/sec

USB ~ 25 MB/sec

Firewire ~30MB/sec

SATA I ~ 40 MB/sec

SATA II ~ 50 MB/s

RAID Sky's the limit depending on flavor up to several hundred MB/sec

10/100 LAN ~ 10 MB/sec

GIG LAN ~ 100 MB/sec


So even allowing for a 3:1 safety factor a lowly USB external HDD can record/playback several (4 -5) HD TV recordings at once.


If you can't record multiple streams without issue, it is some other problem than HDD capability


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Others have suggested a separate drive for the OS. Personally, I think this totally unnecessary presuming you have adequate DRAM to keep your application(s) from paging/swapping.


What IS very helpful, however, is to optimize the access to your drive for these video streams. This suggests two partitions (if not on separate drives).


All you need to do is set up the partition to hold your video files to use 64KB as its "block size". This, coupled with the typical 64KB buffered writes/reads done by your favorite capture/playback software, enables such access to hit the nearly full streaming read and write performance of your disk drive.


Note that the default "block size" is usually 8KB. The difference is quite significant. HDs have tremendously better read and write performance when doing sequential I/O (rather than random) and, at 8KB block size, once you've used your drive for a while, all those 64KB reads and writes end up being quite "random" in nature. Meanwhile, by up'ing the block size to 64KB, a great balance is achieved between read/write rate (from/to the actual disk media) and the seek time it takes the HD to get to the location of the data to be read/written. Indeed, modern drives achieve nearly streaming (i.e. sequential) performance doing "random" 64KB I/Os.


My personal experience is using a lowly laptop drive with the OS partition at 8KB block size and the "Video" partition at 64KB. I'm able to record two ATSC (i.e. around 19.2Mb/s) while playback back a third. I doubt that drive would be able to sustain this performance had I left the "Video" partition at the default 8KB block size of NTFS.
 

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+1 on 64k clusters for the video drive/partition. A separate OS drive can really help if you are doing other CPU and I/O intensive tasks like commercial detection or post recording file compression while recording multiple streams. If you are not doing this then I agree a separate recording partition will work fine


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I also agree with using multiple drives. I use a 80gb drive for the OS. I have two 1.5tb drives for recording TV shows to. I have set the block size to 64k on these data drives. I have 5 Qam tuners that can record 5 shows at the same time, watch a show on the main Tv & watch a show on the bedroom Tv through the HD-200 & never have a hiccup. Very stable.


I use Sage TV which is nice because it will load balance the recordings on the multiple data drives automatically.
 
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