[mythtv-users] Software RAID and ionice

Richard Freeman r-mythtv at thefreemanclan.net
Wed May 23 01:17:39 UTC 2007


David Rees wrote:
> On 5/22/07, Richard Freeman <r-mythtv at thefreemanclan.net> wrote:
>> The raid5 works just fine for mythbackend when the system isn't busy
>> writing to the same disk.
> 
> Which indicates a bottleneck somewhere. ext3 is notorious for blocking
> writes when the journal is flushing which kills performance. Did you
> create the filesystem with the stride option? How big are the stripes
> in your raid array? How many disks and how fast are they?
> 

I answered most of your questions in my other email, but I neglected these.

I did read about the stride option.  I think I have that set 
appropriately.  I forget what I set it to, however...  I think it was 
probably 32 (64K stripe / 4K blocks).

Here is the info for the raid itself - let me know if there is anything 
else that would be of use...:

/dev/md3:
         Version : 00.90.03
   Creation Time : Tue Apr 24 21:22:44 2007
      Raid Level : raid5
      Array Size : 485885696 (463.38 GiB 497.55 GB)
   Used Dev Size : 242942848 (231.69 GiB 248.77 GB)
    Raid Devices : 3
   Total Devices : 3
Preferred Minor : 3
     Persistence : Superblock is persistent

   Intent Bitmap : Internal

     Update Time : Tue May 22 21:02:50 2007
           State : active
  Active Devices : 3
Working Devices : 3
  Failed Devices : 0
   Spare Devices : 0

          Layout : left-symmetric
      Chunk Size : 64K

            UUID : 655984a8:07fe58b4:301f0b57:926cce87
          Events : 0.580

     Number   Major   Minor   RaidDevice State
        0       8       19        0      active sync   /dev/sdb3
        1       8       35        1      active sync   /dev/sdc3
        2       8        3        2      active sync   /dev/sda3




More information about the mythtv-users mailing list