[mythtv-users] ATA RAID Question

[davatar]

If you are doing raid 0 or raid 1 there is no point in using hardware raid
solutions, in fact many (most?) promise "hardware" raid cards are really
software raid, where the raid is implementented in the driver. Might as well
use like MD to make your raid, and not have to deal with horrible closed
source/beta drivers. It's probably faster anyway, especially if it's raid5,
unless you really want no cpu usage. (of course there should be next to
nothing for raid 0/1 anyway) Promise SX4000's with hardware XOR are going
for cheap on ebay though :)

Also about "standard drives" keeping up with SATA drives, the PCI bus
theoretical transfer rate is 133MB/s, with overhead it's much lower. Even on
my nforce2 which is pretty good about it (pretty much nothing on the pci
bus - all hypertransport) I can get about 110-112MB/s.  So ultra ata 133->
SATA 150 makes absolutely no difference. My U3W 160 with a cheetah 15.2k
only gets about 100MB/s :) No SATA drive is going to beat that.

Really I don't know why some of these subjects are magical, just go to the
websites and look up the datasheets, and pay careful attention to the units.
Way too often I find people who think ata133=133Megabits/s, etc. This need
not be "tribal knowledge". You don't need to wait for tomshardware to have a
40 page super-duper-spectacular on hard drive technology either.

Same for video. You want to record at 2200 kbits/8=275 kbytes/sec. Go to any
drive's website/datasheet. Media to host transfer rate will most likely be
way above 20 mbytes/sec.


----- Original Message ----- 
From: "GERALD SCHEPENS" <schepens at shaw.ca>
To: "Discussion about mythtv" <mythtv-users at mythtv.org>
Sent: Tuesday, March 16, 2004 11:19 PM
Subject: Re: [mythtv-users] ATA RAID Question


> I can tell you that Promise's controllers are kind of a pain under Linux.
I have an Asus P4PE with a Promise FastTrac 378 which I got working more by
luck than because of Promise's "fantastic" support.  I've only used
Promise's so far, so I can't compare their support or performance with
anyone else's.
>
> Anyway, a guy I know swears that a decent standard drive with a good cache
will pretty much keep up with an SATA drive.  I don't know what to make of
that claim.
>
> ----- Original Message -----
> From: Karl Rautenstrauch <krautenstrauch at hotmail.com>
> Date: Monday, March 15, 2004 7:07 pm
> Subject: [mythtv-users] ATA RAID Question
>
> > I am looking for a recommendation for an ATA RAID controller.
> > Anyone have a
> > pleasant experience with one they would like to share?  Also, any
> > opinions
> > on whether this would make a difference in a system with 512 MB of
> > RAM and a
> > PVR-250?  In read/write intensive apps like Oracle OLTP databases,
> > we see a
> > huge improvement with RAID 1 or RAID 1+0 and Myth seems fairly IO
> > intense
> > while recording or buffering Live TV.  Thanks in advance.
> >
> > Karl Rautenstrauch
> > Systems Administrator
> > Energy Marketing and Trading
> > Florida Power and Light
> >
> > _________________________________________________________________
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> >
>


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