[mythtv-users] Switching backend IDE drives to libata with 2.6.28 kernel

belcampo belcampo at zonnet.nl
Mon Jun 1 18:23:15 UTC 2009

Tom Dexter wrote:
> I'm in the process of upgrading my various Gentoo machines from 2.6.27
> to 2.6.28.  All the current recommendations call for moving from the
> old IDE drivers (ATA/ATAPI/MFM/RLL) to the new SATA/PATA drivers
> (libata).  I've made the move on one of my non-MythTV boxes and I have
> some questions/concerns about the move, especially regarding my
> backend machine.
> I'd especially like to hear from anyone using the libata with IDE
> drives on their backend machines.
> A number of hdparm settings aren't supported with libata.  The idea is
> to have the kernel just choose the ideal setting.  DMA gets set
> automatically and isn't an issue.  32 bit IO (the -c option) isn't
> supported, but all current opinion indicates that that setting is not
> required these days.  The same goes for the interrupt-unmask (-u).
> The one that has be a little concerned is the multiple sector I/O
> hdparm setting (-m) which isn't supported either.  From what I've seen
> so far, libata seems to default this to 8 when the drives max is 16.
> Except for WD drives, I don't see anything in the hdparm man page that
> would lead me to believe that 8 would be better than 16.  As a matter
> of fact, I never even used the -m option in hdparm, as the old driver
> defaulted to 16.
> My backend has two 500GB Seagate IDE drives.  I haven't had a good
> opportunity to get rid of my lvm partition in favor of storage groups.
>  The lvm spans the drive that also has the / partition and the MySQL
> databases.  I know that's not an ideal setup, but adding a drive would
> be nightmarish, and in any case, it currently works fine the way it
> is.  I can record three HD shows at once while watching another
> previously recorded program with no problems at all.
> I really don't think I can afford to loose even a hint of disk
> performance on that setup, which is why I started looking so carefully
> at this one.  Any advise would be appreciated.
3 HD-shows at an unrealistic 33Mb/s calculates to 100Mb/s = 12.5MB/s
Even an average drive from 2-3 years old does ->50MB/s, this is 
sequential I know, but never the less.
> Tom
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