[mythtvnz] partitions

[Steven Ellis]

On Wed, May 13, 2009 2:37 pm, Sam Hadley-Jones wrote:
> While on the subject of drives and partitions, has anyone looked into
> striping together a bunch of USB flash drives? My current setup is 5x500GB
> WD GP drives in RAID5+LVM for movies and recordings and a 250GB drive for
> OS, swap and torrents. The 250GB drive never gets more than 20GB used and
> I
> don't really need the swap space at all with 2GB of RAM. The RAID array
> spins down after 20 minutes of inactivity using the spindown utility. This
> is a good power saver of about 25W for most of the time but does present
> an
> annoying problem - when you want to watch live TV after the array has spun
> down, it needs around 8 seconds to spin up and will usually fail to start
> live TV a couple of times for those impatiently repeatedly pressing the
> button. What's needed is better access time.
>
> I was thinking that since solid state drives are still relatively
> expensive, I could stripe together 4x 8GB usb sticks on a hub and allocate
> 8GB for OS, 8GB for torrents and 16GB for live TV. The aggregate bandwidth
> of the USB RAID array should be plenty for live TV and the OS. Plus, I'm
> hoping that channel changing will be a bit snappier with the better access
> times of flash.  Wear on the flash memory shouldn't really be a problem
> for
> live TV since it would probably take a week to write over the full 16GB
> space allocated. These flash drives usually state a life of 100,000 writes
> resulting in around 2000 years of average TV viewing. I understand that
> /var will have to be mounted on tmpfs. Is there anything else I need to be
> aware of with this setup? Has someone else here done something similar?

Why not allocate a partition on your 250GB HD for Live TV?

> I'm also looking for a better solution other than LVM for my main RAID
> array. LVM puts too much of a performance hit on the system - I usually
> get
> around 50MB/s sustained! I do like the feature of being able to make
> read-only snapshots for online automated fscking of LVM volumes. It also
> makes migrating drives a lot easier. I've been watching the development of
> ext4 and btrfs as a replacement but I don't know whether they're proven
> reliable yet.

What makes you think LVM is the performance issue here, and what file
system are you using over the top. The way that LVM is implemented you
should see very little performance hit.

For a start run "hdparm -t" on the members of your raid set, and the raid5
device, and an LVM partition and compare the numbers.


Steve
--------------------------------------------
Steven Ellis - Technical Director
OpenMedia Limited - The Home of myPVR
email   - steven at openmedia.co.nz
website - http://www.openmedia.co.nz