[mythtv-users] OT Hardware RAID 5 non-Recommendations
adeffs.mythtv at gmail.com
Wed Dec 20 00:27:25 UTC 2006
On 12/18/06, Brad Templeton <brad+myth at templetons.com> wrote:
> On Mon, Dec 18, 2006 at 08:47:33AM -0500, Steven Adeff wrote:
> > On 12/17/06, Brad Templeton <brad+myth at templetons.com> wrote:
> > > It is also worth considering not doing RAID at all. Seriously.
> > > Yes, drives are failing more often -- though if you keep them cool,
> > > that improves a great deal. Of course, keeping them cool requires
> > > fans you may not want in your living room. I believe you can get
> > > a box that goes in your 5.25" bay zone in larger cases with a 120mm
> > > fan, you can certainly get 92mm fans for such boxes.
> > >
> > > If it's a backend, not in the living room, put in the big, slow fans
> > > for good airflow and low noise.
> > >
> > > RAID as a backup protects you from drive failure, but it does not
> > > protect you from the far more common cause of loss, which is
> > > accidental deletion. It also doesn't protect against the house
> > > burning down or similar troubles.
> > >
> > > You may consider that videos are not as much in need of backup
> > > and that you would rather than 1.5x or 2x the storage than have
> > > backup. Videos can often be recovered over time (shows get run
> > > again) or for those inclined, there are sources on the net where
> > > you might question the ethics of using them for obtaining videos,
> > > but not for recoving ones you legitimately had.
> > >
> > > However, barring that, you may want to consider that
> > > extra drives (as needed for RAID 5) require extra power, heat and
> > > noise. About 10w for a typical drive, which here means $10 per
> > > year or $30 over the 3 year life of a drive. Thus a 750mb
> > > drive may be cheaper than two 400gb drives over time. Not
> > > counting the fancy controller.
> > RAID also gives you speed, which for folks with HDTV becomes
> > important. So with RAID 5 you get a two-fer, speed and "reliability".
> > (plus, what serious TV watcher doesn't do off-site backup of their
> > myth recordings? ;-)
> Speed is not important for HDTV. Full bore 1080i HDTV is about
> 16 megabits/second. Just about any disk you will get today
> will read/write over 300 megabits/second for one disk. (Yes, the
> ATA and SATA busses are much faster than 300 megabits, but
> the disks are not that fast.)
> Truth is, for an HTPC, the slower the disk is, the better,
> because slower disks (ie. 4200 rpm) are quieter, generate
> less heat and fail less frequently. Though you can hardly
> get such slow spinning disks any more.
> When it comes to Myth, raid does one thing for you -- protect
> you from single hard disk failures. A better fan will
> do quite a bit of that, too.
it does with 3 HD tuners and a pvr-150 and two HD capable frontends,
all able to record and playback at the same time with commflagging,
*because* your running RAID.
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