Poor RAID5 performance on new SMP system

["Marc" <linux-raid@liquid-nexus.net>]

Hi,
I recently upgraded my file server to a dual AMD 2800+ on a Tyan Tiger MPX 
motherboard. The previous server was using a PIII 700 on an Intel 440BX 
motherboard. I basically just took the IDE drives and their controllers 
across to the new machine. The strange thing is that the RAID-5 performance 
is worse than before! Have a look at the stats below:

I've fiddled with hdparm making sure the drives are setup correctly 
(dma,32bit,unmaskirq) but without much improvement.

As a comparison I ran the same benchmark against the -single- (root) 
drive /dev/hda and it performed better than the raid array!!

I'm using kernel version 2.4.26 SMP. Do you think upgrading to 2.6.8 would 
improve matters? 

The only guess I can make is that there is an issue with software raid 
performance on an SMP system. 

Any help/suggestions appreciated!

Thanks...


----------------------------------------------------------
Bonnie++ benchmarks:

Before (PIII 700/440BX):

128k chunk
              -------Sequential Output-------- ---Sequential Input-- --
Random--
              -Per Char- --Block--- -Rewrite-- -Per Char- --Block--- --Seeks-
--
Machine    MB K/sec %CPU K/sec %CPU K/sec %CPU K/sec %CPU K/sec %CPU  /sec %
CPU
         1000  7594 85.1 36234 43.0 22728 31.1  8812 96.1 58155 52.5 286.8  
5.6

After: (Dual AMD MP 2800+/Tiger MPX(AMD760)

              -------Sequential Output-------- ---Sequential Input-- --
Random--
              -Per Char- --Block--- -Rewrite-- -Per Char- --Block--- --Seeks-
--
Machine    MB K/sec %CPU K/sec %CPU K/sec %CPU K/sec %CPU K/sec %CPU  /sec %
CPU
         1000 16707 97.7 20745 16.4  9633  9.8 17032 67.2 24741 11.4 194.8  
2.1

/dev/md0:
        Version : 00.90.00
  Creation Time : Sat Apr 17 12:19:25 2004
     Raid Level : raid5
     Array Size : 234444288 (223.58 GiB 240.07 GB)
    Device Size : 78148096 (74.53 GiB 80.02 GB)
   Raid Devices : 4
  Total Devices : 5
Preferred Minor : 0
    Persistence : Superblock is persistent

    Update Time : Mon Oct 18 08:36:52 2004
          State : dirty, no-errors
 Active Devices : 4
Working Devices : 4
 Failed Devices : 1
  Spare Devices : 0

         Layout : left-symmetric
     Chunk Size : 128K

    Number   Major   Minor   RaidDevice State
       0      33        1        0      active sync   /dev/hde1
       1      34        1        1      active sync   /dev/hdg1
       2      56        1        2      active sync   /dev/hdi1
       3      57        1        3      active sync   /dev/hdk1
           UUID : 775f1dcf:7cbc17ab:86e1e792:669b732f
         Events : 0.82

lspci:
0000:00:00.0 Host bridge: Advanced Micro Devices [AMD] AMD-760 MP [IGD4-2P] 
System Controller (rev 20)
0000:00:01.0 PCI bridge: Advanced Micro Devices [AMD] AMD-760 MP [IGD4-2P] 
AGP Bridge
0000:00:07.0 ISA bridge: Advanced Micro Devices [AMD] AMD-768 [Opus] ISA 
(rev 05)
0000:00:07.1 IDE interface: Advanced Micro Devices [AMD] AMD-768 [Opus] IDE 
(rev 04)
0000:00:07.3 Bridge: Advanced Micro Devices [AMD] AMD-768 [Opus] ACPI (rev 
03)
0000:00:10.0 PCI bridge: Advanced Micro Devices [AMD] AMD-768 [Opus] PCI 
(rev 05)
0000:02:00.0 USB Controller: Advanced Micro Devices [AMD] AMD-768 [Opus] USB 
(rev 07)
0000:02:04.0 VGA compatible controller: NVidia / SGS Thomson (Joint Venture) 
Riva128 (rev 10)
0000:02:05.0 RAID bus controller: Silicon Image, Inc. (formerly CMD 
Technology Inc) PCI0680 Ultra ATA-133 Host Controller (rev 02)
0000:02:06.0 RAID bus controller: Silicon Image, Inc. (formerly CMD 
Technology Inc) PCI0649 (rev 02)
0000:02:07.0 FireWire (IEEE 1394): Texas Instruments TSB12LV23 IEEE-1394 
Controller
0000:02:08.0 Ethernet controller: 3Com Corporation 3c905C-TX/TX-M [Tornado] 
(rev 78)

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