[mythtv-users] Slow video on XFS raid 0, ok video on ext3 on single drive.

devsk funtoos at yahoo.com
Mon Jan 1 19:32:57 UTC 2007


>> First, for whatever reason, /dev/md0 does not seem to be my RAID device.

oh boy! you need to know which RAID you are using. software raid provided by linux (MD type) or BIOS raid provided by linux driver device mapper (DM type)? MD type will give you /dev/md0 and DM type will give you /dev/mapper/<blah>. It looks like you are using dmraid and /dev/md0 is a bogus device on your machine (did you mknod it or are there 'fd' type partitions on your disks, which kernel detected automatically). You should do 'fdisk -l /dev/mapper/sil_agbgdgbjfhei' and chose appropriate partition to mount for your mythtv storage.

-devsk

----- Original Message ----
From: Listbox <listbox at hymerfania.com>
To: Discussion about mythtv <mythtv-users at mythtv.org>
Sent: Monday, January 1, 2007 11:17:54 AM
Subject: Re: [mythtv-users] Slow video on XFS raid 0, ok video on ext3 on single drive.

Here is more hdparm data. It looks like bad news.

First, for whatever reason, /dev/md0 does not seem to be my RAID device. I
set up my raid (via trial and error) with dmraid, and it gave me
/dev/mapper/sil_agbgdgbjfhei.
Second, the errors hdparm reports from -tT look significant.
Finally, "Timing cached reads" are much lower then single drives. I don't
know what this really means in a RAID context. 

I tried removing the third drive on the board (primary slave), no effect. I
also tried upping the nice priority of mythbackend. That DID improve the
picture, but not much, and not as good as using the single drive. 

Anyway, given the errors, is this a RAID software problem, or a piece of
junk RAID adapter card?

Thanks so much, folks.

Listbox
* * * * * * * * * * *
* * * * * * * * * * *

/dev/hde:
 multcount    = 16 (on)
 IO_support   =  0 (default 16-bit)
 unmaskirq    =  0 (off)
 using_dma    =  1 (on)
 keepsettings =  0 (off)
 readonly     =  0 (off)
 readahead    = 256 (on)
 geometry     = 19457/255/63, sectors = 312581808, start = 0

/dev/hdg:
 multcount    = 16 (on)
 IO_support   =  0 (default 16-bit)
 unmaskirq    =  0 (off)
 using_dma    =  1 (on)
 keepsettings =  0 (off)
 readonly     =  0 (off)
 readahead    = 256 (on)
 geometry     = 19457/255/63, sectors = 312581808, start = 0

* * * * * * * * * * *
* * * * * * * * * * *


hprarm -tT /dev/md0
read() hit EOF - device too small

/dev/md0:
 Timing buffered disk reads:  read() hit EOF - device too small
BLKFLSBUF failed: No such device
HDIO_DRIVE_CMD(null) (wait for flush complete) failed: No such device

hprarm -tT /dev/mapper/sil_agbgdgbjfhei
/dev/mapper/sil_agbgdgbjfhei:
 Timing cached reads:   HDIO_DRIVE_CMD(null) (wait for flush complete)
failed: Inappropriate ioctl for device
1288 MB in  2.00 seconds = 643.22 MB/sec
 Timing buffered disk reads:  HDIO_DRIVE_CMD(null) (wait for flush complete)
failed: Inappropriate ioctl for device
284 MB in  3.01 seconds =  94.27 MB/sec
* * * * * * * * * * *
* * * * * * * * * * *
* * * * * * * * * * *
* * * * * * * * * * *
dev/hda:
Timing cached reads:   1668 MB in  2.00 seconds = 834.10 MB/sec
Timing buffered disk reads:   88 MB in  3.05 seconds =  28.87 MB/sec

/dev/hdb:
Timing buffered disk reads:  
/dev/hdc:
Timing cached reads:   1696 MB in  2.00 seconds = 847.36 MB/sec
Timing buffered disk reads:   88 MB in  3.05 seconds =  28.82 MB/sec

/dev/hde:
Timing cached reads:   1680 MB in  2.00 seconds = 838.49 MB/sec
Timing buffered disk reads:  168 MB in  3.03 seconds =  55.46 MB/sec

/dev/hdf:
Timing cached reads:   1688 MB in  2.00 seconds = 843.57 MB/sec
Timing buffered disk reads:  164 MB in  3.00 seconds =  54.59 MB/sec

/dev/hdg:
Timing cached reads:   1696 MB in  2.00 seconds = 846.68 MB/sec
Timing buffered disk reads:  162 MB in  3.03 seconds =  53.45 MB/sec

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