[mythtv-users] Fastest RAID for HD?

[Ryan]

I drool just reading your email about your servers!  lol

On Feb 16, 2008 11:00 AM, Marc <drayson at net1plus.com> wrote:

> Markus Schulz wrote:
> > Am Freitag, 15. Februar 2008 schrieb Marc:
> > [...]
> >> Don't assume people on this list are experts. Some are, some are
> >> informed users who have done research, some just make assumptions
> >> based off of one post or one article they read.
> >>r severs
> >> >From a statistical standpoint..
> >>
> >> Raid0 would be the fastest, it is common sense. Your speed for any
> >> action would be dependent on the number of drives you had or N.
> >> However if one drive fails you lose all data.
> >>
> >> Raid3 or 5 would be the second fastest and would be safer due to the
> >> ability to continue working without loss of data if you had a single
> >> drive fail. The difference between these 2 raid types is the way they
> >> setup parity. Raid3 has a dedicated parity drive. Raid5 spreads
> >> parity across all the drives.
> >> Speed of any action on either of these raid configs would be the
> >> number of drives you had minus 1 or N-1.
> >
> > sorry but thats not true. Show me a raid5 with 5-6 drives which will got
> >> 300MB/s _write_ performance...
> >
> > Fastest Raid _WITH_ redundancy was raid10.
> >
> >
>
> The high dollar hardware raid controllers will get close to the N-1 rate,
> I
> have benchmarked them under sustained load, but the hardware raid are in
> the
> $500-$1000 range, and raid10 with 6 disks will in a perfect world be
> 180-210mb/second (3 effective drives-60-70mb/second/drive).   RAID10 is
> really
> on the fasted RAID if you are benchmarking seek times (database), if you
> are
>
> benchmarking raw sequential read and write rates with a good controller
> both are about the same speed with raid5/6 or with raid10, and even raid0
> only gives a 10-20% gain over raid5/6.    Raid10 only really wins when one
> is doing a lot of seeks as small write seeks are expensive on raid5.
>
> Most software raid has a problem that most of the older MB controllers and
> cheaper controller cards really don't have independent channels and
> interfere
> with each other.   On mine I get 70MB/second with one disk, and then it
> goes
> to 108mb/second with a second dd added and then to 115 with a 3rd, so the
> controller is utter crap, but still I can get 40MB/second writes out of it
> with raid5 and it is good enough.    With the good controllers that goes
> 70,140,
> 210,280 and I have tested good controllers and they do exist, one just has
> to
> be more careful in finding them, and a lot of the recent MB controllers
> are
> good controllers.
> _______________________________________________
>
> I used to have a Raid10 for my video storage, but it filled up too quick.
> I decided against switching to Raid0 due to not having any fault
> tolerance.
> I saw Raid3/5 as the best option due to more storage space, like Raid0 but
> with FT.
> Raid5 became my choice for this as we used it at work with great success.
> We
> have servers with 2 (raid0), 6 (raid5), 16 (2x8 drives in raid5 then
> striped), and 24 (3x8 drives in raid5 then striped) drive configurations.
> Each system except for the 2 drive server has 2 HDD mirrored for the OS
> and
> the other drives are for media storage.
> I drool over what I could do with these in a myth setup hehe.
>
>
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