Re: default hdparms? readahead=256? Re: WD 400GB xATA Drives

[Mark Lord <lkml@rtr.ca>]

Linda Walsh wrote:
>..
> set to known values may not contain "great values".  My "readahead"
> value seems to boot with a value of "256" for all of my drives.
> 
> Is this not a bit "excessive"?

Wow.. that does look a bit HUGE.  Thanks for pointing it out,
I'm resetting mine back to 128 for now.

> Justin Piszcz wrote:
>> When I write to this disk for a while, I see this in dmesg (only once 
>> so far):
>>
>> [31230.223504] ata6: translated ATA stat/err 0x51/04 to SCSI 
>> SK/ASC/ASCQ 0xb/00/00
>> [31230.223511] ata6: status=0x51 { DriveReady SeekComplete Error }
>> [31230.223515] ata6: error=0x04 { DriveStatusError }
>>
>> Is there some sort of smart testing going on constantly?  I only get 
>> 26-27MB/s on this 400GB/SATA/16MB/7200RPM drive.  I use smartmontools 
>> to do a daily test.  However, even with smart disabled, I get:
>>
>> # hdparm -t /dev/sde
>> /dev/sde:
>>  Timing buffered disk reads:   78 MB in  3.06 seconds =  25.46 MB/sec
>>
>> Does anyone know if this drive has problems in Linux or something?
>>
>> [    6.895914]   Vendor: ATA       Model: WDC WD4000KD-00N  Rev: 01.0
...

Some drives suck at sequential reads, in favour of doing random seeks
very very well.  Basically, the on-drive seek algorithm may not favour
doing much read-ahead.  Try "hdparm -A1" and see if that helps.