[mythtv-users] 64bit IDE RAID options?

Steve Adeff adeffs at gmail.com
Tue Jan 10 03:48:04 UTC 2006


On Monday 09 January 2006 21:53, Trey Boudreau wrote:
> On Mon, Jan 09, 2006 at 07:42:28PM -0500, Steve Adeff wrote:
> > On Monday 09 January 2006 17:36, Trey Boudreau wrote:
> > > On Mon, Jan 09, 2006 at 12:26:18PM -0800, Yeechang Lee wrote:
> > > > James C. Dastrup <jc at dastrup.com> says:
> > > > > Is anyone aware of a PCI-X  64bit / 133MHz capable IDE RAID HBA?
> > > > > Or, how about a PCI  64bit / 33 Mhz MHz capable IDE RAID HBA?
> > > >
> > > > People generally consider 3Ware's 7xxx (ATA) and 8xxx/9xxx-series
> > > > (SATA) cards, which all support 64-bit/66MHz PCI-X, the standard for
> > > > high-quality, reasonably-priced, true hardware RAID cards. (Or just
> > > > for JBOD, as I'm doing with two 7506-4 cards and eight 400GB ATA
> > > > drives I'm using in part for MythTV.)
> > >
> > > I *really* like the performance of my Areca ARC-1120 8 port SATA PCI-X
> > > card.  It beats the pants off of my 3ware 7450 and 8506.  I don't know
> > > how it compares to  the 9xxx-series controllers.  Unfortunately, the
> > > last time I checked the Areca folks hadn't got their drivers into the
> > > kernel tree (2.6.14-mumble).  It annoyed me to have to unpack the
> > > archive and tweak the Kconfig file, but I eventually got over it
> > > (mostly ;-).
> > >
> > > -- Trey
> >
> > whoa, $600 for a controller card!  I think I can live with software RAID,
> > rather spend the money on a faster cpu...
>
> No amount of CPU cycles will get you the disk bandwidth lost to software
> RAID5 back:
>
> Hardware RAID5 write of one 512-byte disk block:
> write 512 bytes over PCI
> (controller card updates the parity without causing PCI bus activity)
>
> Software RAID5 write of one 512-byte disk block:
> read 512 bytes of parity over PCI
> write 512 bytes of data over PCI
> write 512 bytes of modified parity over PCI
>
> At best you can amortize the parity I/O over "n" blocks, where "n"
> equals the number of disks in your RAID5 set minus one.  Given MythTV's
> propensity for creating large files, you can get this level of
> performance much of the time.  Even so, you never get those bus cycles
> back.
>
> -- Trey

ahh... true, didn't think of that. I also found a few linux-compatible 
hardware RAID5 SATA 4+ disc PCI/PCIX/PCIE cards for under $200 on ebay.

-- 
Steve


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