Re: [Sheflug] Disk Activity Problems

[Barrie Bremner <xxxxx [at] xxxxxxxxxxxxxxxxx>]

>>>>> "Robert" == Robert Pumphrey <rob.pumphrey [at] certus-tech.com> writes:

    Robert> Barrie, Thanks for that, I just turned on DMA using

    Robert> hdparm -d 1 /dev/hda

    Robert> and disk copying just flys. A 2 minute operation now takes
    Robert> 2 seconds.  Thanks.

    Robert> /dev/hda: multcount = 0 (off) I/O support = 0 (default
    Robert> 16-bit) unmaskirq = 0 (off) using_dma = 1 (on)
    Robert> keepsettings = 0 (off) nowerr = 0 (off) readonly = 0 (off)
    Robert> readahead = 8 (on) geometry = 4863/255/63, sectors =
    Robert> 78125000, start = 0

    Robert> These are my current settings. What will happen if I start
    Robert> to twiddle with multcound & I/O Support?  Having set this
    Robert> parameter once, will I have to set it after each re-boot?
    Robert> (I know I can find this out by re-booting, but I would
    Robert> rather not have to)

    Robert> Thanks again.

Rob,

How's this affecting the load settings?

Probably the best thing is to have a look through man fdisk.

There are various warnings of possible data loss if you set things to
something your drive may dislike, so don't say I didn't warn you :-)
This is only for particular options - and they have plenty warnings
next to them.

If you want to set all this at boot time, put a line in your boot
scripts.  On my Redhat machine I've added the following line to
/etc/rc.local/:

hdparm -q -a1 -q -c3 -q -d1 /dev/hde

The -q option just means 'do the following option quietly'.

If you run hdparm -a1 -c3 -d1 /dev/hda from the command line to check
it works before adding the line to /etc/rc.local you should get
something like:

[root@flux root]# hdparm -a1 -c3 -d1 /dev/hde 

/dev/hde:
 setting fs readahead to 1
 setting 32-bit I/O support flag to 3
 setting using_dma to 1 (on)
 I/O support  =  3 (32-bit w/sync)
 using_dma    =  1 (on)
 readahead    =  1 (on)


It'll generally throw errors if it doesn't like something.

For geekiness, you can check how this affects things using

hdparm -Tt /dev/hda

i.e:

[root@flux root]# hdparm -Tt /dev/hde

/dev/hde:
 Timing buffer-cache reads:   128 MB in  1.26 seconds =101.59 MB/sec
 Timing buffered disk reads:  64 MB in  2.81 seconds = 22.78 MB/sec

Note, these numbers are affected by the load on the system, disk
access at the time, phase of the moon, etc, etc.

Have fun!

Baz.


-- 
Barrie J. Bremner		OpenPGP public key ID: F78CEE08
baz [at] barriebremner.com	http://barriebremner.com/


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