[mythtv-users] SATA and DMA (SIIG 3112)

[Brian Wood]

On Mar 31, 2006, at 2:26 PM, leland sindt wrote:

> What does "hdparm -tT" show you?
>
> hdparm -tT /dev/sda
>
> /dev/sda:
>  Timing cached reads:   2256 MB in  2.00 seconds = 1127.93 MB/sec
>  Timing buffered disk reads:  112 MB in  3.08 seconds =  36.41 MB/sec
>
>
>  Two SD and one HD stream is a *lot*  of data, you may be hitting  
> the real limit of the drive system.
>
> Yes, it is a lot of data... My orig plan was to use a SATA II  
> controller
> (but didn't know at the it required pci-e at the time)


There is no (n)ATA drive available on the market at this time that  
can even keep up with a SATA-150 interface. The so-called SATA-II  
(not really a standard yet) may be interesting in the future but  
right now it belongs to the marketing people and not the engineers.

>
> Hmmm... Anybody got numbers/experience with Hardware/Software Raid  
> 0? Did it result in increased bandwidth?
> (Less likely with software, I know)


I record on a RAID-0 software  array with 2 SATA drives:

/dev/hda:
Timing cached reads:   2608 MB in  2.00 seconds = 1303.92 MB/sec
Timing buffered disk reads:  184 MB in  3.00 seconds =  61.33 MB/sec


/dev/md0:
Timing cached reads:   2648 MB in  2.00 seconds = 1323.92 MB/sec
Timing buffered disk reads:  338 MB in  3.03 seconds = 111.62 MB/sec

Which is more or less what you'd expect, given a little overhead for  
the software RAID.