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

Andrew Lyon andrew.lyon at gmail.com
Tue Jan 2 01:09:00 UTC 2007


On 1/1/07, Listbox <listbox at hymerfania.com> wrote:
> Yes,
>
> I mount /dev/mapper/sil_agbgdgbjfhei2 as my mythtv storage. I never
> understood the difference between
> "software raid" and "BIOS raid" till now. That's why it took me so long to
> set up via trial and error. Thanks!
>
> I don't think that is the source of my performance problems though....
>
> Listbox
>
> ________________________________
>
> From: devsk [mailto:funtoos at yahoo.com]
> Sent: Monday, January 01, 2007 11:33 AM
> To: Discussion about mythtv
> Subject: Re: [mythtv-users] Slow video on XFS raid 0,ok video on ext3 on
> single drive.
>
>
> >> 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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Dont be so sure, ive seen dmraid performance like this before, try
software raid, its much better anyway.

Andy


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