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Top Forums Programming write() issue during a low level hdd access Post 302397288 by sponnusa on Sunday 21st of February 2010 06:10:44 PM
Old 02-21-2010
thank you.

So, there is no way around it without writing a device driver to handle the read/write operations? Is that right?

I have a utility written in python which able to identify the bad sectors exactly as the same way as the C program. I am not sure, if python would have implemented anything internally (a device driver) to achieve this. I'm currently downloading the python source code to analyse.

I am sure C is more low level then python (which is btw the dumbest statement, i've said Smilie) and should be able to achieve it. It's little weird that the program fails to identify the bad sectors. I have analysed the following programs so far for such an implementation. And all have the same code.

Testdisk, dd, ddrescue, badblocks etc.,.

So does this conclude that the none of the above available usermode linux opensource programs are really doing what they are claiming for? (data recovery / forensics utilities?) All the above program implements O_DIRECT options too.

Well, I guess I am in need of a fix now! Smilie

It also sounds a little weird that there are no user mode programs (not even one?) available in linux that can do a direct I/O with the disk. (Except that I am willing to write one using the libata / scsi libraries which can directly talk to the ATA (PATA / SATA) devices using ATA protocol (i've done this in dos using assembly) and SG / SCSI protocol to the scsi devices).

Anyways, thanks for all your input and guidance. Atleast it got me to do the O_DIRECT implementation. Please update this thread if there are any more information to be shared / assisted.

Thanks again for all the help. Smilie
 

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STRESS(1)							   User Commands							 STRESS(1)

NAME
stress - tool to impose load on and stress test systems SYNOPSIS
stress [OPTION [ARG]] ... DESCRIPTION
`stress' imposes certain types of compute stress on your system -?, --help show this help statement --version show version statement -v, --verbose be verbose -q, --quiet be quiet -n, --dry-run show what would have been done -t, --timeout N timeout after N seconds --backoff N wait factor of N microseconds before work starts -c, --cpu N spawn N workers spinning on sqrt() -i, --io N spawn N workers spinning on sync() -m, --vm N spawn N workers spinning on malloc()/free() --vm-bytes B malloc B bytes per vm worker (default is 256MB) --vm-stride B touch a byte every B bytes (default is 4096) --vm-hang N sleep N secs before free (default is none, 0 is inf) --vm-keep redirty memory instead of freeing and reallocating -d, --hdd N spawn N workers spinning on write()/unlink() --hdd-bytes B write B bytes per hdd worker (default is 1GB) --hdd-noclean do not unlink files created by hdd workers Example: stress --cpu 8 --io 4 --vm 2 --vm-bytes 128M --timeout 10s Note: Numbers may be suffixed with s,m,h,d,y (time) or B,K,M,G (size). SEE ALSO
The full documentation for stress is maintained as a Texinfo manual. If the info and stress programs are properly installed at your site, the command info stress should give you access to the complete manual. stress 1.0.1 August 2009 STRESS(1)
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