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

Tom Dexter digitalaudiorock at gmail.com
Mon Jun 1 18:05:09 UTC 2009

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.


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