02-22-2006
Some day I will benchmark a few runs of dd and find the optimal setting, if there is one. I have only dd'ed magnetic disks. Never dd'ed a cd-rom, let alone a dvd. So I'll stay with what I know. Use the rdsk style device, not the dsk so the data goes to straight your data segment (not via the buffer cache). The rdsk driver has to read whole sectors. If you ask for a piece of a sector, it may not work. Or it may read a sector and discard what you don't want. I stay with a multiple of 1024. Bigger is better than tiny. But after a point, the advantage starts to taper off. 1 MB is the smallest size I would consider trying. I will want to mentally estimate how much is left, etc...so no screwball sizes. I wind up with N * (1 MB) where N is some small integer. 10 MB seems like a nice round number. We have one bad spot on the disk. I expect dd to fail when it gets there. I will restart it on the next 10 MB chunk. So I have doomed myself to having a 10 MB hole in my disk. That is pretty much my thought process as I picked my blocksize.
It would be a disaster to pick a buffer size so large that box starts to page. I have plenty of memory on this box, so no problem there.
10 More Discussions You Might Find Interesting
1. SuSE
Sir,
I using the following commands in a file (part of a bigger script):
#!/bin/bash
cd /opt/oracle/bin
ls -lt | tail -1 | awk '{print $6}' >> /tmp/ramb.out
If I run this from the command prompt the result is:
2007-05-16
if I run it as a cron job then... (5 Replies)
Discussion started by: rajranibl
5 Replies
2. Shell Programming and Scripting
Hi ,
I have a piece of code ...wherein I need to assign the following ...
1) A command line argument to a variable
e.g origCount=ARGV
2) A unix command to a variable
e.g result=`wc -l testFile.txt`
in my awk shell script
When I do this :
print "origCount" origCount --> I get the... (0 Replies)
Discussion started by: sweta_doshi
0 Replies
3. AIX
AIX:Command to get netaddress/subnet address command in IPv4/IP6
Can anybody help us with a command to retrieve netaddress/subnet address command in IPv4/IP6 on aix machine.
net/subnet address is in the format 172.16.212.0(signifies all 255 machines in an IPv4 network) (2 Replies)
Discussion started by: rookie8278
2 Replies
4. Shell Programming and Scripting
Hi everyone,
when executing this command in unix:
echo "WM7 Fatal Alerts:", $(cat query1.txt) > a.csvIt works fine, but running this command in a shell script gives an error saying that there's a syntax error.
here is content of my script:
tdbsrvr$ vi hc.sh
"hc.sh" 22 lines, 509... (4 Replies)
Discussion started by: 4dirk1
4 Replies
5. UNIX for Advanced & Expert Users
Hi,
Well my title isn't very clear I think. So to understand my goal:
I have a script "test1"
#!/bin/bash
xvkbd -text blabla
with xbindkeys, I bind F5 key in order it runs my test1 script
So when I press F5, test1 runs.
I'm under Emacs/Vi and I press F5 in order to have "blabla" be... (0 Replies)
Discussion started by: xib.be
0 Replies
6. UNIX for Dummies Questions & Answers
HI Guys,
I hope you are well. I am trying to write a script that gets executed every time i open a shell (cshell). I have two questions about that
1) I need to enter these commands
$ echo $DISPLAY
$ setenv $DISPLAY output_of_echo_$display_command
How can i write a... (2 Replies)
Discussion started by: kaaliakahn
2 Replies
7. Shell Programming and Scripting
I am working with a sh script on a solaris 9 zone (sol 10 host) that grabs information to build the configuration command line. the variables Build64, SSLopt, CONFIGopt, and CC are populated in the script. the script includes
CC=`which gcc`
CONFIGopt=' --prefix=/ --exec-prefix=/usr... (8 Replies)
Discussion started by: oly_r
8 Replies
8. Shell Programming and Scripting
below is the output xml string from some other command and i will be parsing it using awk
cat /tmp/alerts.xml
<Alert id="10102" name="APP-DS-ds_ha-140018-componentFailure-S" alertDefinitionId="13982" resourceId="11427" ctime="1359453507621" fixed="false" reason="If Event/Log Level(ANY) and... (2 Replies)
Discussion started by: vivek d r
2 Replies
9. AIX
exec(): 0509-036 Cannot load program /usr/opt/freeware/bin/rpm because of the following errors:
0509-022 Cannot load module /opt/freeware/lib/libintl.a(libintl.so.1).
0509-150 Dependent module /opt/freeware/lib/libiconv.a(shr4.o) could not be loaded.
0509-152 Member... (4 Replies)
Discussion started by: Ohmkar
4 Replies
10. UNIX for Beginners Questions & Answers
Hello Forum,
I'm making very good progress on my report thanks to the very helpful people on this forum. I've been able to successfully create my report for my Red Hat servers. But I do have a few ubuntu servers in the mix and I'd like to capture some data from them when an ssh connection is... (8 Replies)
Discussion started by: greavette
8 Replies
cmdk(7D) Devices cmdk(7D)
NAME
cmdk - common disk driver
SYNOPSIS
cmdk@target, lun : [ partition | slice ]
DESCRIPTION
The cmdk device driver is a common interface to various disk devices. The driver supports magnetic fixed disks and magnetic removable
disks.
The block-files access the disk using the system's normal buffering mechanism and are read and written without regard to physical disk
records. There is also a "raw" interface that provides for direct transmission between the disk and the user's read or write buffer. A sin-
gle read or write call usually results in one I/O operation; raw I/O is therefore considerably more efficient when many bytes are transmit-
ted. The names of the block files are found in /dev/dsk; the names of the raw files are found in /dev/rdsk.
I/O requests to the magnetic disk must have an offset and transfer length that is a multiple of 512 bytes or the driver returns an EINVAL
error.
Slice 0 is normally used for the root file system on a disk, slice 1 as a paging area (for example, swap), and slice 2 for backing up the
entire fdisk partition for Solaris software. Other slices may be used for usr file systems or system reserved area.
Fdisk partition 0 is to access the entire disk and is generally used by the fdisk(1M) program.
FILES
/dev/dsk/cndn[s|p]n block device (IDE)
/dev/rdsk/cndn[s|p]n raw device (IDE)
where:
cn controller n
dn lun n (0-7)
sn UNIX system slice n (0-15)
pn fdisk partition(0)
/kernel/drv/cmdk 32-bit kernel module.
/kernel/drv/amd64/cmdk 64-bit kernel module.
ATTRIBUTES
See attributes(5) for descriptions of the following attributes:
+-----------------------------+-----------------------------+
| ATTRIBUTE TYPE | ATTRIBUTE VALUE |
+-----------------------------+-----------------------------+
|Architecture |x86 |
+-----------------------------+-----------------------------+
SEE ALSO
fdisk(1M), mount(1M), lseek(2), read(2), write(2), readdir(3C), scsi(4), vfstab(4), attributes(5), dkio(7I)
SunOS 5.10 9 Oct 2004 cmdk(7D)