how to enable cache flushes for hard disk?

[Jan Evert van Grootheest]

Kaimi,

	-----Oorspronkelijk bericht-----
	Van: busybox-bounces at busybox.net
[mailto:busybox-bounces at busybox.net] Namens kaimi
	Verzonden: dinsdag 22 mei 2007 10:35
	Aan: busybox at busybox.net
	Onderwerp: Re: how to enable cache flushes for hard disk?
	
	
	Another question, on my pc, the hd supports cache flushes, it
shows:
	
	[root at localhost linux-2.6.20-dm]# hdparm -T /dev/hdb
	
	/dev/hdb:
	 Timing cached reads:   3344 MB in  2.00 seconds = 1671.72
MB/sec
	
	and my target board does not support cache flushed, it shows:
	[root at test tmp]# ./hdparm -T /dev/hda
	
	/dev/hda:
	 Timing cached reads:    68 MB in  2.04 seconds =  33.30 MB/sec
	
	I don't know if this feature is the inducement, I want to
disable this feature on pc, what's the command? thanks  

Cache flushes are only relevant to writes. So the above cannot be
explained with cache flush support.
The above is *read* performance. Most likely the difference is because
of hardware differences.
 
Try something like 'hdparm -I /dev/hda'  on both and carefully check
which mode the disk is using.
That command will also indicate whether cache flush support is available
on the disk (and then again it may still not be used by Linux due to
other issues).
 
-- Jan Evert




	On 5/22/07, kaimi <dishui at gmail.com> wrote:

		hi,all
		    I want to enable cache flushes for my hd on s3c2410
& linux-2.6.20, ide_id_has_flush_cache() return 0 because cfs_enable_2
is 0x201, while it needs 0x3000, I found out that 0x201 was from 512
bytes of id info,implemented in static void ata_input_data(ide_drive_t
*drive, void *buffer, u32 wcount) 
		the question is, does it mean my hd does not support
cache flush on hw layer? if not, how to enable?
		thanks for the coming help!
		
		Rgrds
		Kaimi 
 
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