<div class="gmail_quote">On Thu, Jun 18, 2009 at 5:45 PM, Stephen Worthington <span dir="ltr"><<a href="mailto:stephen_agent@jsw.gen.nz">stephen_agent@jsw.gen.nz</a>></span> wrote:<br><blockquote class="gmail_quote" style="border-left: 1px solid rgb(204, 204, 204); margin: 0pt 0pt 0pt 0.8ex; padding-left: 1ex;">
<div class="im">On Thu, 18 Jun 2009 13:30:55 +1200, you wrote:<br>
<br>
>On Thu, Jun 18, 2009 at 12:57 PM, James Booth <<a href="mailto:james@booths.net.nz">james@booths.net.nz</a>> wrote:<br>
>> I end up with three frontends all watching and recording HD at the same<br>
>> time.<br>
>><br>
>I wouldn't worry too much about the performance - hard drives are at least<br>
>an order of magnitude faster than HD streams. I believe TV3 runs around<br>
>11Mbps, a modern drive will easily handle in excess of 400Mbps. A two disk<br>
>RAID1 should be capable of nearly twice the single disk read speed - when<br>
>you've got multiple reads going (as its the case with streaming three files<br>
>to different frontends) RAID1 should be approximately the same speed as<br>
>RAID0 for the same number of drives.<br>
<br>
</div>You are missing the point a bit when you refer to disk speed only in<br>
Mbit/s. That is a useful number only when the disk is being used for<br>
just one data stream. If there are four tuners writing to the disk,<br>
another recorded program being played, and the four new recordings are<br>
being commercial scanned, then there are 9 data streams being used and<br>
the disk heads are going to have to be moving between them all. </blockquote><div><br>You're right about this, but note that I was talking about reading only, as was James. As I said RAID 0, 1, and 5 can all have pretty similar performance (per disk) reading multiple streams. But if you've got 4 or more recordings going at once you are probably much better off using separate filesystems on separate disks with storage groups. If you're really worried about losing recordings then set up a couple of separate RAID1s with storage groups. That will probably perform better than a single RAID array of any type.<br>
<br>Cheers,<br>Steve<br></div></div>