|
RAID (Redundant Arrays of Independent Disks) comes various
flavors, with RAID-0 (striping) and RAID-1 (mirroring) being the most common.
RAID can either be done in hardware (using a controller like the ubiquitous
PROMISE RAID chips and controllers) or in software.
On-board RAID controller chips by Promise (e.g. on the
Asus A7V) should get detected by the installer and work. The HPT368 (UDMA/66
RAID) should work, too, but might require some special boot loader parameters
(read the 'HPT366 chipset support' paragraph in /usr/src/linux/Documentation/Configure.help).
If you want to use a controller card, you will usually have to download and
install drivers from the vendor's page. The IDE controller
list on linhardware.net has more information on this topic. Another valuable
source of information is RAID
solutions for Linux.
 section index  top
S.M.A.R.T. is the 'Self-Monitoring, Analysis and Reporting
Technology' used in most modern IDE hard drives. It is used to check the
reliability of the drive and predict drive failures. To put this technology
to use in GNU/Linux, you need to enable S.M.A.R.T. in your system's BIOS
and you need a program like the UCSC S.M.A.R.T. Suite
or ide-smart (
Mandrake Contrib RPM). They allow you to run tests (even periodically)
and will warn you, if drive parameters drift out of range (indicating an
upcoming drive failure).
Handling is very simple (as 'root'):
ide-smart -d /dev/[device] -q
will run a quiet test, only returning messages if there
was an error.
section index top
-
The first rule is to refrain from connecting any
kind of slave device to a port which already has an IDE master disk. If you
really need a second disk, use the second port, and if you've already got
a CD/DVD there, get a controller card.
-
The second rule is to keep cables as short as possible.
The longer the cable the higher the possibility of data transfer errors.
-
More RAM ;-). GNU/Linux makes a generous use of
RAM for caching disk accesses. Low memory resources will lead to thrashing
(i.e. swapping memory to and from the hard disk). Yes, there is the swap
file, but the best swap file is an unused swap file!
-
Think big! Larger disks are (usually) faster. Remember
however that more speed in most cases also means more heat and more noise.
The rest is done via 'hdparm'. If you have a look at
'hdparm's man page, you might feel slightly uneasy: lots of options and every
now and then disheartening messages like Use with extreme caution!
or may result in severe file system corruption!.
Those of you who are familiar with M's history might remember the infamous
6.0 initscript bug, where a 'hdparm' parameter lead to freezes on some systems.
Later on, using 'hdparm' optimization became an installation option along
with an appropriate warning. It has been removed again since because it caused
trouble on some systems.
It isn't all that dangerous provided you know what you
are doing and if you use the right options. And the disk speed will increase
significantly even with the conservative settings I'm going to describe here.
hdparm -i /dev/hd[x] will tell you everything
you need to know about your hard disk(s), like model name, geometry, supported
(U)DMA and PIO modes. The currently active transfer mode is marked with an
asterisk (*).
hdparm /dev/hd[x] shows you adjustable
parameters and their current setting.
hdparm -Tt /dev/hd[x] runs a benchmark.
Knowing benchmarks, you should run several of them to get meaningful results.
You can ignore the 'Timing buffer-cache reads' value, this one varies widely
even within minutes. Really important is the second value, 'Timing buffered
disk reads'. I will refer to this value in the next section.
Optimization Examples
Since I usually use hdparm, I've set all
parameters to '0', which turns them off. In this setting I get around 3.5
MB/sec.
I turn on 32-bit I/O support. I'm using setting '3' which is slightly slower
than '1' but more secure:
hdparm -c3 /dev/hda
Now the benchmark shows a value around 5.8 MB which
is already a significant increase.
What about (U)DMA?
hdparm -d1 /dev/hda
The benchmark takes a huge leap up to 15 MB/sec. Note
that this command will automatically put the drive to the highest available
transfer mode (UDMA/33 here), so there is no need to specify the -X34
option.
And that's all there is to it: hdparm -c3d1 /dev/hda.
Other settings like -m16 (enabling multiple sector count) or
-u1 (unmasking interrupt) have no effect whatsoever,
but might even be dangerous.
You might have heard about the hd[x]=autotune
boot parameter. This also shows no effect here.
Mandrake Linux user Roger shares his thoughts:
"One could either add to '/etc/lilo.conf':
append=" hda=dma hdb=dma hdd=ide-scsi quiet hdc=ide-floppy
opti"
I'm also seeing some other options for the append line
in 'lilo.conf' such asidex=ata66, but I have yet to have time
to grep the kernel source or test this option to see if it works.
Or, for Mandrake 8.1, I added a new file, called '/etc/rc.d/init.d/hdparm-settings':
#Tweak drives for best speeds!
#WDC WD273BA 27.3GB 66MB/sec 7200RPM UDMA4
hdparm -c1 -m0 -d1 -X68 -S253 /dev/hde
# WDC WD400BB-00AUA1 40GB 100MB/sec 7200RPM UDMA5
hdparm -c1 -m0 -d1 -X69 -S253 /dev/hdg
# WDC WD102BA 10.2GB 66MB/sec 7200RPM UDMA4
hdparm -c1 -m0 -d1 -X68 -S253 /dev/hdf
Now, add this to your run level. I used /usr/bin/ksysv (as
root) to add this to my run-level 5. An easier and less messy way of
doing this is just adding these few lines anywhere inside your '/etc/rc.d/rc.local',
only con is that it will execute at the end of the boot process. Since I
have ultra dma hdd's, I enabled udma option by adding the "-X" option. Not
well documented in the man page of hdparm, so here's the options for "-X":
33 multiword DMA mode1
66 UDMA2
68 UDMA4 (My two Ultra66 hdd's support this)
69 UDMA5 (My Ultra100 hdd supports this)
To find out of which your hdd supports & is currently
set to, do the following:
# hdparm -i /dev/hdx
DMA modes: mdma0 mdma1 mdma2 udma0 udma1 udma2 udma3 udma4 *udma5
There's another option called multcount,
but enabling this to either 8 or 16, resulted in a loss of tx speeds in my
drives. Read the man page for hdparm for more info.
I'm also not seeing much in improvement by enableing UDMA4/5 but, my drives
support it so why not? Eh? Just be advised that messing with these options
could cause corruption with your filesystem, so be safe and make regular
backups. The '-c' option is obsolete from what I've just read. It was
mainly used on drives prior to 66/100 drives. The '-S240' option is not needed...it
only sets the 'sleep option' for the hdd's to ~20 minutes."
Mandrake Linux user Hoyt Duff adds:
"You might want to give the boot option ide0=0x1f0
a try. It forces the use of a more modern IDE driver. Also,floppy=daring
can really speed up modern floppy drives -- 'mtools' just zip along."
Sleep Mode
hdparm not only optimizes speed but also
allows you to define a standby timeout (hdparm -S[xxx]), after
which your drive will spin down to save power. The values follow a somewhat
peculiar scheme, which is explained in man hdparm.
Notice that the hard drive 'sleep' function puts a great
deal of mechanical strain on the hard drive when 'waking it up'. Furthermore
does the Linux drive access cache prevent a drive with mounted partitions
on it from going into 'sleep' mode. The 'noflushd' package from your Mandrake
Linux CD enables you to work around that. You should make sure to its man
page before using it, though.
Once you've found a suitable setting, execute the 'hdparm'
command again, adding the 'k' option. This will preserve your settings beyond
the current session.
section index top
|
