Re: Partitioning for Speed
Alvin Oga, 2003-Mar-31 17:03 -0800:
>
> hi ya
Greetings
> On Mon, 31 Mar 2003, Jeff wrote:
>
> > I've seen a reference to two regarding the location of a partition on
> > the HDD being faster than other parts of the HDD. I've been trying to
> > get a definitive answer on this and it's still not clear to me.
>
>
> the disk spins at the same rotational rpm ... its the "same" speed
Now that I sit and think about that, I see it now.
> what you can do, is to add more data ( sectors ) on a given tract
> say 64 sectors per track vs 256 sectors on the outer tracks
> ( doing so screws up your pll and other analog signals
> ( but is worth it if you want to maximize capacity
>
> - whether reading 64* 512bytes/sector or 256 * 512byte/sector
> is better/worst is up to the app ... and how data is written
I'll have to ponder this for awhile. Don't quite get it yet.
> - less moving of the heads is generally faster as it takes too long
> to move the head relative to just reading data
>
>
> - track 0 ( first partitions ) is ALWAYS on the outside of the disk
Thanks for clearing that up for me.
> - example pic of partition layout on the disk
>
> http://www.linux-1u.net/Partition/
Fantastic web site! I'll be spending some time there. Pictures are
good!
> - careful selection of bytes per sector also helps
> 512 byte /sector vso 1024 or 2048 bytes/sector
> ( bytes per inode )
>
> - but all that is lots-o-headaches
> and you'd need to write data to disk to take those extra
> tweeks into account for maximum benefit
Uhuh.
> - calculate ... 5400rpm vs 7200rpm vs 10,000rpm vs 15,000rpm
> - defaults is 512 bytes/sector
> - defaults is 64 sectors per track
> - defaults is "n" number of physical heads ( number of platters )
>
> - for each revolution of disk ... you get xxxKB/sec of disk
> transfer
>
> - ignore all those marketing numbers of ata-66, ata-100,
> ata-133
>
> - for ide disks -- 1st round no-brainer speed comparason/optimization
>
> - fiddle with some of the hdparm options and check its effects
>
> - hdparm -tT /dev/hda
>
> - hdparm -d 1 -u 1 -m 16 -c 3 /dev/hda
> ( make sure your disk supports the options first )
>
> - turn on dma ( -d 1 )
> - turn on intr ( -u 1 )
> - turn on multicount ( -m 16 )
> - turn on 32bit io ( -c 3 )
>
> - set the proper ATA speed ( -X69 for ata-100 )
>
> http://www.linux-1u.net/Disks/hdparm.txt
I've spent time learning how to use hdparm and have been able to boost
performance for my drives most of the time. I haven't gotten anything
better than around 20Mbps, but that's better than 4.
>
> - dont forget to account for 2MB disk cache and 8MB disk cache
>
> - simpler to just add a 2nd spindle ( /dev/hdc ) and be able
> to read data 2x faster than with one disk ( /dev/hda )
> - initial writing of data and parity will be slightly slower
>
> - other ways to improve your system
>
> http://www.linux-1u.net/Tuning/
Thanks Alvin. I've got some studying to do. :-)
jc
--
Jeff Coppock Systems Engineer
Diggin' Debian Admin and User
Reply to: