I don't think with any RAID setup you can add another drive unless it's the same size as the others in the array, so extending a RAID setup can/could be difficult, you could easily have a RAID1 array with two 1TB drives and a LVM on top then make another RAID1 array with another two, say, 2TB drives and extend the LVM across the two RAID1 setup's. Also unless you want a real performance hit I'd shy away from splitting your 1TB drive into 2 500G partitions and adding them into the same RAID array as the data would then be written to the same physical drive twice.<br>
<br>p.s I'm now running ext4 on my main storage drive, so far no problems... touch wood.<br><br>Tim<br><br><div class="gmail_quote">2009/6/18 Stephen Worthington <span dir="ltr"><<a href="mailto:stephen_agent@jsw.gen.nz">stephen_agent@jsw.gen.nz</a>></span><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>
><br>
>> Thanks Steve. RAID1 with LVM will give me what I need, I was just hoping<br>
>> for RAID 1+0 so I could also get the performance gain, which may be handy if<br>
>> I end up with three frontends all watching and recording HD at the same<br>
>> time. If I had three RAID1 arrays as per Tim’s email, and then put RAID0<br>
>> over the top, could I subsequently add in another RAID1 pair as per Tim’s<br>
>> directions, and then grow the RAID0 across the extra RAID1 pair without<br>
>> having to backup? I guess in short I’m asking can you currently add<br>
>> disks/partitions to a RAID0 automatically without loss of data? I find many<br>
>> conflicting answers on the net.<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. The<br>
Linux caching algorithms are good, and will reduce the head movement a<br>
lot, but there will still have to be head movement. And while the<br>
read and write speeds for modern 7200 rpm SATA drives are quite<br>
staggeringly big, the stepping rates have not changed in ages and are<br>
still a *lot* slower than even quite old 10k or 15k SCSI drives.<br>
<br>
That said, my two Seagate 7200.10 500 Gibyte data drives combined as<br>
one LVM/JFS partition cope well with the above scenario, but only at<br>
MPEG data rates from my PVR-500 tuners. I have yet to move my DVB-T<br>
tuners onto the Myth box to find out if they will work as well when<br>
there are two 1080i and two 720p programs being recorded at the same<br>
time.<br>
<div class="im"><br>
>As far as I know you can't extend RAID0 arrays with mdadm either (at least<br>
>the man page says 1/4/5/6 only). My advice is that if you're really<br>
>expecting to extend the array any time soon just buy the drive now.<br>
><br>
>By the way, that stuff you keep referring to from Tim's email was also<br>
>written by me :-)<br>
><br>
>Cheers,<br>
>Steve<br>
<br>
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</div></div></blockquote></div><br><br clear="all"><br>-- <br>Regards<br>Tim, Donna and Erin Gibson<br>