[mythtv-users] thoughts on a combined backend/NAS box?

[jedi]

On Tue, Jul 16, 2013 at 10:22:23AM -0400, Joseph Fry wrote:
> On Tue, Jul 16, 2013 at 10:06 AM, Jim Oltman <jim.oltman at gmail.com> wrote:
> 
> > On Tue, Jul 16, 2013 at 3:37 AM, Tim Draper <veehexx at gmail.com> wrote:
> >
> >> On 16 July 2013 06:55, GZ <gzornetzer.lists at gmail.com> wrote:
> >> > Hi all,
> >> > I've been thinking about upgrading my mythtv setup and at the same time,
> >> > I've also been looking at buying a RAID5 NAS box.  After looking at the
> >> > price tags on some of those enclosures, I'm thinking about just
> >> building a
> >> > combination RAID / mythbackend box.  I've read some of the guidance on
> >> the
> >> > wiki, indicating that RAID really isn't the best way to go for the
> >> mythtv
> >> > recording drive.  I'm thinking about the following drive setup:
> >> >
> >> > 1 SSD for the OS/database
> >> > 1x 1 tb for active recording (my existing recordings drive.
> >>  Eventually, I
> >> > may just upgrade this to a 3tb drive that would act something like an
> >> in-use
> >> > hot spare
> >> > 4x 3tb drives in RAID5 for archive storage (pictures / long-term video
> >> > archive)
> >> >
> >> > Since all of my tuners are now external (HDHR prime & usb QAM), I'm
> >> thinking
> >> > about a microitx motherboard to keep this box smallish (corner of my
> >> > office).  There are a few H77 boards with 6 total SATA ports an H87
> >> board
> >> > with 6x 6gbps sata.  I figure that a 4-core ivy bridge or haswell
> >> process
> >> > has plenty of juice for this.
> >> >
> >> > Couple of things that I'd like to do:
> >> > - It would be cool to move shows from the recording drive to the archive
> >> > upon lossless transcode.  Do I have to write custom transcode rules to
> >> do
> >> > this?
> >> >
> >> > - I'd like to use ACPI wakeup to reduce power usage on this system.
> >>  This
> >> > means that I'm going to need some way to lock mythbackend when I want
> >> to use
> >> > the NAS functionality.  I suppose that I could run some mythfrontends
> >> on the
> >> > client, but that's pretty kludgy.  How complex is it to code up a client
> >> > that connects to mythbackend enough to bump the usage count and block
> >> > shutdown?  Alternatively, does anyone have a good way to trigger a
> >> > mythwelcome lock and unlock commands remotely over the network?
> >> >
> >> > Any advice or thoughts are welcomed.
> >> > Thanks very much,
> >> > -Greg
> >>
> >
> > I'll just put out there that no one in their right mind should ever use
> > RAID5.  It's just not safe.  I'd recommend at least RAID6 or possibly
> > RAID10 if you're paranoid.  Remember, if a disk fails in RAID5, you need to
> > resilver the array.  That can take time.  What if another disk were to die
> > during the resilver?  You'd be screwed.  And don't think it won't happen to
> > you.  It happened to me.  It was awful.  Luckily, I managed to grab most of
> > my data.
> >
> 
> There is nothing wrong with RAID 5... but you have to be aware that it
> cannot be used in place of a backup, just like any RAID solution.  The odds
> of a two disk failure are far lower than a single disk... so while the
> potential is there, odds are it won't happen and in the meantime your
> system will keep chugging along while the array rebuilds.

    A single RAID 10 array still lacks sufficient redundancy and isn't really
any better than a RAID5 array. You really need at least 2 copies of your data
if you really care about it. Nothing short of this is going to be really any
improvement. It will just be more expensive.

    Ragging on one variety of RAID versus another is really just polishing
the brass on the Titanic.