Poweredge 840 /w centos 5.0

[Jobe Bittman]

Look in your fstab. Are these disks mount with all the exact same
parameters?

On 11/9/07, Drew Weaver <drew.weaver at thenap.com> wrote:
>
>  I'm having disk performance issues on centos 5.0 on a pe 840
>
>
>
> We're not using a raid array although the disks are attached to a raid
> controller (we are using the disks separately)
>
>
>
> SCSI subsystem initialized
>
> Fusion MPT base driver 3.04.02
>
> Copyright (c) 1999-2005 LSI Logic Corporation Fusion MPT SAS Host driver
> 3.04.02
>
> ACPI: PCI Interrupt 0000:02:08.0[A] -> GSI 16 (level, low) -> IRQ 169
>
> mptbase: Initiating ioc0 bringup
>
> ioc0: SAS1068: Capabilities={Initiator}
>
> scsi0 : ioc0: LSISAS1068, FwRev=000a3100h, Ports=1, MaxQ=286, IRQ=169
>
>   Vendor: ATA       Model: WDC WD2500JS-75N  Rev: 2E04
>
>   Type:   Direct-Access                      ANSI SCSI revision: 05
>
> SCSI device sda: 488281250 512-byte hdwr sectors (250000 MB)
>
> sda: Write Protect is off
>
> sda: Mode Sense: 73 00 00 08
>
> SCSI device sda: drive cache: write back SCSI device sda: 488281250
> 512-byte hdwr sectors (250000 MB)
>
> sda: Write Protect is off
>
> sda: Mode Sense: 73 00 00 08
>
> SCSI device sda: drive cache: write back
>
>  sda: sda1 sda2 sda3
>
> sd 0:0:0:0: Attached scsi disk sda
>
>   Vendor: ATA       Model: WDC WD2500JS-75N  Rev: 2E04
>
>   Type:   Direct-Access                      ANSI SCSI revision: 05
>
> SCSI device sdb: 488281250 512-byte hdwr sectors (250000 MB)
>
> sdb: Write Protect is off
>
> sdb: Mode Sense: 73 00 00 08
>
> SCSI device sdb: drive cache: write back SCSI device sdb: 488281250
> 512-byte hdwr sectors (250000 MB)
>
> sdb: Write Protect is off
>
> sdb: Mode Sense: 73 00 00 08
>
> SCSI device sdb: drive cache: write back
>
>  sdb: sdb1
>
> sd 0:0:1:0: Attached scsi disk sdb
>
>
>
> as you can see the system correctly sees both disks (SDA and SDB)
>
>
>
> we notice the performance on SDB is about ½ of what SDA is getting:
>
>
>
> [root at x-q0 ~]# time dd if=/dev/sda of=/dev/null bs=65536 count=10000
> skip=10000 0
>
> 10000+0 records in
>
> 10000+0 records out
>
> 655360000 bytes (655 MB) copied, 10.6832 seconds, 61.3 MB/s
>
>
>
> real    0m10.685s
>
> user    0m0.004s
>
> sys     0m0.935s
>
> [root at x-q0 ~]# time dd if=/dev/sdb of=/dev/null bs=65536 count=10000
> skip=10000 0
>
> 10000+0 records in
>
> 10000+0 records out
>
> 655360000 bytes (655 MB) copied, 19.4021 seconds, 33.8 MB/s
>
>
>
> real    0m19.404s
>
> user    0m0.009s
>
> sys     0m0.923s
>
>
>
> does anyone have any tips as why this might be happening?
>
>
>
> Should we just use the ports on the motherboard and remove the raid
> controller altogether?
>
>
>
> Thanks,
>
> Andrew
>
>
>
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>



-- 
Jobe Bittman
Chief Network Architect
ZenGarden, Inc.
(858) 200-6099
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