[mythtv-users] Slightly OT: Moving from drive slowing down entire system

jacob jacob at heider.homelinux.net
Tue Sep 5 00:53:18 UTC 2006


On Mon, Sep 04, 2006 at 08:24:12PM -0400, Ryan Steffes wrote:
> >> I'm recovering from a hard drive failure, and I'm trying to copy my DVD
> >> library to the new drive.  For some reason, I seem to be getting
> >> rediculously bad performance on my brand new SATA drive.  Copying a file
> >> from the old corrupted drive to the new drive can take twenty to thirty
> >> minutes per file.  As it's a SATA drive, hdparm doesn't really play nice
> >> with it, but all the DMA stuff seems to be set correctly in the bios.
> >>
> >> Check your dmesg. It is highly likely that the old drive is retrying the
> >reads many times.
> >
> >I do get some complaints about the bad blocks in dmesg, but why does that
> >practically lock up the entire system?
> >
> >Ryan
> >
> 

try 'nice top'. It should show you an incredible amount of usage in
(most likely) hi (hardware interrupt) or, possibly, si (software
interrupt). Those interrupts demand immediate attention of the kernel,
and trump anything userspace might want. I'm sure those badblock
interrupts are firing frequently, as they do with bad drives, and taking
your resources. If you want to watch, try:

watch -d -n1 cat /proc/interrupts

and the numbers associated with, ide0, I presume, should be advancing
rapidly.

> 
> Sorry about replying to myself, but just realized I didn't post the full
> timing results:
> 
> /dev/sda:
> Timing cached reads:   1412 MB in  2.00 seconds = 705.75 MB/sec
> HDIO_DRIVE_CMD(null) (wait for flush complete) failed: Inappropriate ioctl
> for device
> Timing buffered disk reads:  196 MB in  3.02 seconds =  64.98 MB/sec
> HDIO_DRIVE_CMD(null) (wait for flush complete) failed: Inappropriate ioctl
> for device
> [root at mythtv mythtv]# hdparm -tT /dev/hdb
> 
> /dev/hdb:
> Timing cached reads:   1384 MB in  2.00 seconds = 691.07 MB/sec
> Timing buffered disk reads:  186 MB in  3.03 seconds =  61.48 MB/sec
> [root at mythtv mythtv]# hdparm -tT /dev/hda
> 
> /dev/hda:
> Timing cached reads:   1412 MB in  2.00 seconds = 705.75 MB/sec
> Timing buffered disk reads:   12 MB in  3.60 seconds =   3.34 MB/sec
> [root at mythtv mythtv]#
> 
> 
> hda is the bad drive, incidentally.  It just seems these times are bad all
> around, but I expected the new drive to be better, at least over 1k.
> 
> Ryan

Um, 65MB/s and 61.5MB/s are excellent read speeds. Those should be the
physical limit of the drive. What were you expecting?

Jacob


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