[mythtv-users] Planning Tuners and Disk I/O for a MythTVBackend System

[Jim Beckett]

Travis Tabbal wrote:
>
>
>     Will the new sda1 partition be large enough, or is 60GB too big?
>
>
>
> What's it for? The OS/DB? If so, drop it and put the OS/DB on a 
> different drive. An old IDE drive will work fine, SSD if you really 
> want performance. I used an old 40GB IDE drive from an old TiVo, it 
> worked great. With 12 tuners you might want something a little more 
> speedy for the DB though. 
>
> Sharing the OS and DB with the recordings is a recipe for lots of 
> seeks, hosing your I/O speed. Put your swap on the OS drive as well. 
> For the size of the system you're talking about, the disks holding 
> recordings should hold ONLY recordings. I'd partition them into a 
> single partition with XFS. Don't share spindles, it's not worth it. 
> Why the live TV partition? Just let Myth balance the I/O by putting 
> the whole-drives in the same storage group. If you find your I/O 
> system can't keep up, add more disks to the storage group. For this 
> reason, unless you need huge space, I'd buy 500G or smaller drives and 
> just use more of them. If you can't fit more disks in there, time to 
> set up a dedicated backend box. 
>  
>
>     I see XFS, and EXT4, talked about a lot for large file types.
>     Which of these, or possibly another, would be the best choice for
>     the recordings directory?
>
>
>
> EXT4 does pretty well with large files, but I still like XFS for 
> recordings. Set the pre-allocation size up around 500M and you will 
> keep fragmentation low. Again, keeps seeking down. 
>
>  
>
>     I'm thinking FAT32 on the USB drive for portability, if I ever
>     want to mount it temporarily on another system. Shouldn't be a
>     problem for MythTV, should it?
>
>
>
> It will work, but be more fragile. Back up the data somewhere just in 
> case. Which you should be doing anyway. 
>
>  
>
>     Lastly, I have 2GB of RAM installed in this system, should I even
>     bother with the swap partition?
>
>
>
> My backend has 2GB and rarely uses any swap. It's also running other 
> processes. So you might be able to get away without swap, I generally 
> put it in anyway though. If a process needs to use it, it generally 
> doesn't just it long.  
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Travis,

Great points! This is exactly the kind of advice I was seeking...

The answer to the question of why I have a LiveTV partion is, 'I don't 
know, It seemed like a good idea at the time'... IIRC, I think I was 
trying to grasp the 'storage groups' concept at the time- 
http://www.mythtv.org/wiki/MythVideo_.22_Transition_Guide

I do have a 320GB IDE drive in a computer in storage that I can use for 
the OS, DB, SWAP, and Multimedia, that is on the USB disk now. I don't 
know why this didn't occur to me before... (I seem to be racking up the 
"DUH" moments lately...)

Using this drive would allow me to use both of the SATA drives for 
recordings only, and provides enough extra space that I could use my USB 
drive as a portable again, which eliminates my need for shared data 
directory.

Doing it this way, my new configuration would look like this:

/dev/hda (IDE internal disk) - 320GB IDE (298GB formatted)

   hda1, 96GB, mount point /, Ext3
   hda2, 200GB, mount point /multimedia, XFS (for videos, music, and 
pictures)
   hda4, 2GB, SWAP
  
/dev/sda (first SATA internal disk) - 500.1GB SATA (460GB formatted)

   sda1, 460GB, mount point /recordings1, XFS

/dev/sdb (second internal disk) - 500.1GB SATA (460GB formatted)

     sdb1, 400GB, mount point /recordings2, XFS


Which strikes me as a very simple way to get the most out of my existing 
drives...

So, this is the route I think I want to take, unless there is a 
compelling reason not to do it this way.

Thank you!

-Jim
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