[CentOS] Poor RAID performance new Xeon server?

Stewart Williams lists at pinkyboots.co.uk
Tue Jan 13 18:52:25 UTC 2009


John R Pierce wrote:
> Stewart Williams wrote:
>> John R Pierce wrote:
>>   
>>> Stewart Williams wrote:
>>>     
>>>> The block I/O is the thing that concerns me as mostly I am serving a 
>>>> 650MB file via samba to 5 clients and I think this is where I need the 
>>>> speed.
>>>>       
>>> is this a sequential or random access application thats using this 
>>> file?   is it read only/mostly, or is it random update?
>>>     
>> I'm not sure, how can I find this out?
>>   
> 
> well, what is the nature of the application thats using this file?     
> do you really mean just a single 650MB (sub 1GB) file?
> is this something like a quickbooks file? (thats kind of what it sounds 
> like from your other answers).
> 
> given what you have now, and what information we've been given, I would
> 
>     A) disable BIOS raid, configuring it for JBOD w/ ACHI enabled
>     B) mdadm mirror disks 0 and 1, and put the OS on that
>     C) mdadm mirror disks 2 and 3, and put your shared SMB filesystem on 
> that

I disabled RAID in the BIOS (with SATA native mode set to auto), and the 
CentOS install runs fine to start with, then I setup my RAID 
configuration in disk-druid, continue and the system virtually grinds to 
a halt when it get's to the formating filesytem stage; the progress bar 
goes up a little then stops. The mouse cursor moves and the disk light 
flashes frequently but nothing is happening (even after hours). I can't 
switch to a debugging VT as the system is so un-responisve.

However, if I enable the RAID in the BIOS again, and proceed with the 
above, the install finishes fine.

Upon POST it says 4 drives JBOD.

The only thing that concerns me is that the drives are running at best 
speeds and not in PIO mode as William stated. I assume as I have created 
the array with mdadm and not HP's config utility that this is not the 
case, but just want some clarification.

CentOS loads the ahci driver and it looks OK to me. Here is my dmesg output:

scsi0 : ahci
scsi1 : ahci
scsi2 : ahci
scsi3 : ahci
ata1: SATA max UDMA/133 abar m2048 at 0xec000800 port 0xec000900 irq 233
ata2: SATA max UDMA/133 abar m2048 at 0xec000800 port 0xec000980 irq 233
ata3: SATA max UDMA/133 abar m2048 at 0xec000800 port 0xec000a00 irq 233
ata4: SATA max UDMA/133 abar m2048 at 0xec000800 port 0xec000a80 irq 233
ata1: SATA link up 1.5 Gbps (SStatus 113 SControl 300)
ata1.00: ATA-7: GB0250C8045, HPG1, max UDMA/133
ata1.00: 488397168 sectors, multi 16: LBA48 NCQ (depth 31/32)
ata1.00: configured for UDMA/133
ata2: SATA link up 3.0 Gbps (SStatus 123 SControl 300)
ata2.00: ATA-7: MAXTOR STM3250310AS, 4.AAA, max UDMA/133
ata2.00: 488397168 sectors, multi 16: LBA48 NCQ (depth 31/32)
ata2.00: configured for UDMA/133
ata3: SATA link up 1.5 Gbps (SStatus 113 SControl 300)
ata3.00: ATA-7: MAXTOR STM3250310AS, 3.AAF, max UDMA/133
ata3.00: 488397168 sectors, multi 16: LBA48 NCQ (depth 31/32)
ata3.00: configured for UDMA/133
ata4: SATA link up 3.0 Gbps (SStatus 123 SControl 300)
ata4.00: ATA-7: MAXTOR STM3250310AS, 4.AAA, max UDMA/133
ata4.00: 488397168 sectors, multi 16: LBA48 NCQ (depth 31/32)
ata4.00: configured for UDMA/133

Also, it shows 2 of the ports are running as 3.0Gbps (which is strange 
as I thought all of the ports on the mainboard were the same 1.5Gbps speed)

The 3 maxtor drives were purchased as SATA2 spec.

Is there a way to tell what ata?.00 corresponds to sd[a-d]? So that I 
can RAID the 2 faster drives together. Or does the kernel assign in 
order (e.g. ata2.00 = sdb)? Or won't it make much difference?

Thanks

Stewart



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