[mythtv-users] LVM2 Striping Suggestions...

Sun Sep 24 15:48:56 UTC 2006

Well if you plan on having three/four SD streams and later adding some
HD streams of recording, you may want to plan for that now. Recording
HD requires significantly more in terms of disk I/O (and CPU). Search
the list archives for more info on Hi-Def disk and CPU requirements as
I am not currently doing any hi-def capture/playback.

On 9/23/06, Andy Speagle <sidrew at gmail.com> wrote:
> Well... I reckon I'm talked into RAID... I will now have four (4) 250GB
> ATA-100 WD2500JB Drives ... I'll throw them together in a software RAID 5
> setup... writing across that many spindles should be fairly nice... I doubt
> software RAID 10 would work very well... (but might be cute to see)...
>
> When you say:
>
> > (providing your not planning on high def)
>
> What is it that you mean?...
>
> Thanks,
>
> Andy
>
> On 9/23/06, Robin Smith <1canuck2 at gmail.com> wrote:
> > AFTER buying my hardware RAID card I read a few things that implied
> > software RAID may actually be better (at least that hw RAID is not as
> > good as its cracked up to be unless you are buying a real server class
> > RAID controller ($$$). Your choice of CPU and the Gig of RAM should
> > set you up well (providing your not planning on high def) so I'd think
> > you'll be fine. The PVRs use little to no CPU when recording, so
> > Myth-wise you're not going to be taxing your CPU that much...
> >
> > On 9/23/06, Andy Speagle < sidrew at gmail.com> wrote:
> > > Ok.. fair enough.. g etting the drives is a trivial matter... and I
> suppose I
> >
> > > can understand not wanting to lose recordings... I consider the PVR a
> > > convenience rather than a long term storage system for TV... but setting
> up
> > > RAID isn't that much of a stretch.
> > >
> > > The one caveat to that is that I don't have hardware RAID available to
> me
> > > for the ATA-100 drives... and while I've had much fun with linux
> software
> > > RAID setups... I'm curious if doing software RAID with this system would
> be
> > > too much...
> > >
> > > Does anyone have any insight about performance with linux RAID?
> > >
> > > Thanks,
> > >
> > > Andy
> > >
> > >
> > > On 9/23/06, Robin Smith < 1canuck2 at gmail.com> wrote:
> > > > I work in IT, so statistically, my odds may be higher. For IBM
> > > > Deskstar drives (Deathstar's as we used to call them), our failure
> > > > rate was a whopping 9% until they released new firmware. We are on
> > > > Western Digital Caviar drives and the failure rate is still around 4%.
> > > > My RAID5 array uses four Samsung Spinpoint SATA drives (which are
> > > > quiet). I started out with just two, LVM together as you are
> > > > describing, and one of the bastard drives died! I got it replaced
> > > > under warranty and then bit the bullet and bought two more drives and
> > > > a RAID card as I was not happy with the risk. The type of failure I am
> > > > describing are happening within the first two months of buying the
> > > > drive, so I think its an issue with DOA states not lifepsan stats. I
> > > > also have other PCs where I have been running four 80GB drives for
> > > > four years no problem, so I can attest to some drives also having long
> > > > lifespan. Unfortunately, it seems like its a gamble though. I do not
> > > > buy cheap drives either, these are all high quality brand name drives.
> > > >
> > > > My thought on data integrity versus performance:
> > > > I'll take data integrity any day. First of all, the performance you
> > > > will get without striping will NOT be poor, so the striping issue is
> > > > somewhat moot as I'd consider it uneccesary, even with four streams
> > > > recording and one playing back. Data integrity was one of my goals (as
> > > > well as quiet sexy looking HTPC), primarily because:
> > > > 1. It takes a long time to set up a good Mythbox and I don't want to
> > > > repeat the tasks in a panic when something goes wrong with a disk.
> > > > 2. I don't want to lose my recordings. Sure its "just" TV, but why
> > > > invest the time and effort to setup a PVR and record/archive stuff if
> > > > you don't mind if it gets lost? I would be pissed if I lost my current
> > > > set of recordings. I don't want to have to archive to DVD in a timely
> > > > fashion because I fear for the loss of data, that's just not
> > > > convenient for me.
> > > >
> > > > That's my perspective anyway. To sum up, I'd basically challenge you
> > > > with: why stripe and increase your risk of data loss when it is
> > > > completely uneccessary based on your current plans? You don't need the
> > > > striping performance, so don't bother taking the risk it brings.
> > > > Return one of your PVR350s, spend the money on a third 250GB disk and
> > > > set up RAID5. Four simultaneous recordings sounds cool, but how often
> > > > are there four things on at one time that you won't get through
> > > > timeshifting? Three is still an awesome number of simultaneous
> > > > recordings...
> > > >
> > > > Robin
> > > >
> > > >
> > > > On 9/23/06, Andy Speagle < sidrew at gmail.com> wrote:
> > > > > I had the same feelings about drive lifespan... and I agree that the
> > > data
> > > > > isn't exactly mission critical... anything that I would want to keep
> > > would
> > > > > be exported on DVD or <insert media here>.  I'd rather sacrifice
> data
> > > > > integrity for my media than performance...  It's going to be fun to
> play
> > > > > with this setup... as I've done this with old bt878 cards on low-end
> > > systems
> > > > > as a test... but never on real production quality equipment.
> > > > >
> > > > > Thanks.
> > > > >
> > > > > Andy
> > > > >
> > > > >
> > > > > On 9/23/06, Michael MacLeod <mikemacleod at gmail.com> wrote:
> > > > > > If these are new drives, I suspect that the lifetime of the drive
> is
> > > > > longer than the lifetime of his currect mythtv install. Maybe if
> you've
> > > been
> > > > > recycling the same drives through systems for the last ten years you
> can
> > > > > expect them to die on you, but seriously, two new drives are going
> to
> > > last a
> > > > > while.
> > > > > >
> > > > > > RAID5 for a bunch of television shows is overkill. This isn't
> mission
> > > > > critical data here, and the disks in all likelyhood are going to
> last at
> > > > > least a few years. Maybe I'm just lucky, but I've never had a drive
> fail
> > > > > inside a desktop system (I've had a laptop drive fail when the
> laptop
> > > failed
> > > > > to go to sleep when the lid closed and then went for a journey on
> the
> > > > > subway, but those are different circumstances). I've been running
> four
> > > of my
> > > > > drives for over five years now, and they still work fine. Although,
> at
> > > four
> > > > > years, I did start mirroring the data on another set of drives.
> > > > > >
> > > > > >
> > > > > >
> > > > > > On 9/23/06, Eric Ladner < eric.ladner at gmail.com> wrote:
> > > > > > > On 9/23/06, Robin Smith < 1canuck2 at gmail.com> wrote:
> > > > > > > > Yikes! Having been burned by too many dead hard drives in my
> life,
> > > I
> > > > > > > > would never consider this option... you are essentially double
> > > your
> > > > > > > > chances of complete data loss.
> > > > > > >
> > > > > > > I agree completely.  Either buy another drive and do RAID5, or
> > > mirror
> > > > > > > the pair you have.  It might not happen today or tomorrow, but
> > > > > > > eventually, you'll loose 500GB of data when ONE of your 250GB
> drives
> > > > > > > fail.
> > > > > > >
> > > > > > > As for throughput, consider that the average show (my average
> anyway
> > > -
> > > > > > > I turn my settings up for better quality) is about 2.5 Gig.
> That
> > > > > > > works out to about 650K per second.  I'd figure you'd have to
> have
> > > > > > > about 8 to 10 streams running at the same time before you'd
> start to
> > > > > > > see problems.
> > > > > > >
> > > > > > > My 0.02
> > > > > > > --
> > > > > > > Eric Ladner
> > > > > > > _______________________________________________
> > > > > > > mythtv-users mailing list
> > > > > > > mythtv-users at mythtv.org
> > > > > > >
> > > http://mythtv.org/cgi-bin/mailman/listinfo/mythtv-users
> > > > > > >
> > > > > >
> > > > > >
> > > > > > _______________________________________________
> > > > > > mythtv-users mailing list
> > > > > > mythtv-users at mythtv.org
> > > > > >
> > > http://mythtv.org/cgi-bin/mailman/listinfo/mythtv-users
> > > > > >
> > > > > >
> > > > > >
> > > > >
> > > > >
> > > > > _______________________________________________
> > > > > mythtv-users mailing list
> > > > > mythtv-users at mythtv.org
> > > > >
> http://mythtv.org/cgi-bin/mailman/listinfo/mythtv-users
> > > > >
> > > > >
> > > > >
> > > > _______________________________________________
> > > > mythtv-users mailing list
> > > > mythtv-users at mythtv.org
> > > >
> http://mythtv.org/cgi-bin/mailman/listinfo/mythtv-users
> > > >
> > >
> > >
> > > _______________________________________________
> > > mythtv-users mailing list
> > > mythtv-users at mythtv.org
> > > http://mythtv.org/cgi-bin/mailman/listinfo/mythtv-users
> > >
> > >
> > >
> > _______________________________________________
> > mythtv-users mailing list
> > mythtv-users at mythtv.org
> > http://mythtv.org/cgi-bin/mailman/listinfo/mythtv-users
> >
>
>
> _______________________________________________
> mythtv-users mailing list
> mythtv-users at mythtv.org
> http://mythtv.org/cgi-bin/mailman/listinfo/mythtv-users
>
>
>