Linux x86_64 frozen by heavy I/O on PE2950 with PERC 5/i

[Jeffrey Paul]

On 4 August, 2008, at 05:33, <Ram_Sevak at Dell.com> wrote:

> Paul,
> You might want to tune /proc/sys/vm parameters as suggested in this
> thread:
> http://lists.us.dell.com/pipermail/linux-poweredge/2008-April/035855.htm
> l
>
> Thanks
> Ram


I've done so (trying with percentages of 1, 5, 10) to no avail.  All  
this does is cause the system to freeze up faster sooner in the  
copying process.  I really don't think this is a write-buffer issue.

It does nothing to solve the problem that the disk i/o is abysmally  
slow.  I'm seeing around 6mB/sec on writes to a two-disk RAID1 of 1TB/ 
7200RPM/32MB disks.  These disks perform above 30mB/sec for sequential  
writes individually in other systems.

I have a script that contains "dd if=/dev/zero of=testfile bs=1M  
count=2000 && sync".  The box has zero load.  Doing a sync to clear  
any existing buffers, then timing that script yields 5m30s, or 6mB/ 
sec.  It's also worth noting that during those 5 minutes, it takes 2-3  
minutes just to open an SSH connection to the machine.  I think this  
is indicative of a problem somewhere other than the OS write cache.

Additionally, I've updated the system BIOS to the latest version as  
well:

HOST ~ # getSystemId
Libsmbios:    0.13.6
System ID:    0x01B2
Service Tag:  redacted
Express Service Code: redacted
Product Name: PowerEdge 2950
BIOS Version: 2.3.1
Vendor:       Dell Inc.
Is Dell:      1
HOST ~ #

So I've got the latest in-kernel driver for the raid card, the latest  
raid card firmware, and the latest system bios installed.

Any other ideas?

Cheers
-jp

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