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George Mari wrote:
<blockquote cite="mid:494BB89F.4080109@mari1938.org" type="cite">
<pre wrap="">Jake Anderson wrote:
[deleted]
</pre>
<blockquote type="cite">
<pre wrap="">For me its a few personal experiences.
I have a raid 0 setup (started before storage groups were available) and
if I watch something whilst something else is being recorded and
commflagged the little blue light is almost solid on. I had to add more
ram to the machine to let it record 2 shows and watch a 3rd. I needed to
go to 2gb of ram from 1gb, adding a further 2gb helped some more too.
My fathers myth box which is a P4 3ghz (vs my Q6600) was doing about the
same job (without the commercial flagging, but as that is in realtime on
my machine it shouldn't affect disk IO much at all) will record 2 shows
and watch a 3rd with 512mb of ram and the disk light flashes at about
1-2 Hz.
</pre>
</blockquote>
<pre wrap=""><!---->
Well, to be fair, with RAID 0,5 or 6, (and probably 1), your drive light
will be on more or at least as much as with a non-raid, single drive
solution. You're just spreading the same number of IO operations
(slightly more with RAID5 or 6 because of the parity info) over multiple
drives/spindles, so your system as a whole can do more IO.
</pre>
</blockquote>
The thing is though you need to look at the "cost" of the drive IO<br>
The thing that takes a drive the longest is seeking, so if you are
trying to write 2 data streams simultaneously to a disk you can expect
to see a greatly degraded speed. Writing one stream per drive means the
head is going to already be pretty much in the right position when the
next block of data comes along, IE minimal seek time, vs thrashing the
head around writing small chunks faster.<br>
<br>
Its the same as copying files from one drive to another, its much
faster (for large files) to copy them sequentially rather than to try
and do it simultaneously. <br>
<br>
Or putting different database tables onto different drives,
same/similar reason.<br>
<blockquote cite="mid:494BB89F.4080109@mari1938.org" type="cite">
<pre wrap="">
If you have a 1GB system that is a combined BE/FE, that's probably a
little tight on RAM, especially when comm flagging, mythfilldatabase and
possible transcode jobs run at the same time, so you may have been
cutting into the swap space, and not necessarily hitting the IO limits
of your RAID0.
</pre>
</blockquote>
swap wasn't paticularly active, it was running mythbuntu so it's pretty
light.<br>
<blockquote cite="mid:494BB89F.4080109@mari1938.org" type="cite">
<pre wrap="">
I have a dedicated BE with 576MB RAM and an old SCSI card with 6x180GB
drives in a software RAID5. It's no trouble recording 2 shows, comm
flagging them, and watching 3 other shows on my different FEs. It sits
in the basement, and is obviously not suitable for a living room or
bedroom, but it's hardware I had lying around or was able to procure
inexpensively.
[deleted]
</pre>
</blockquote>
Those are rather high end disks, with low seek times. I was/am using
generic ATA drives.<br>
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