Tagged Questions

3
votes
1answer
234 views

Measure hard-disk read(), write() speed without caching in QNX 6.5

I am working on QNX 6.5 Operating system. QNX 6.5 supports POSIX APIs. I am trying to build an application which is used to evaluate performance of hard-disks. My application will read/write/read ...
2
votes
0answers
161 views

Local disc copy at 10MB/s! What could be the problem?

I am running a Debian 6.0.6 (before you ask). I have a regular desktop computer, nothing fancy... but when I copy a file using nautilus I am getting 10MB/s copy speed and the system is completely ...
1
vote
1answer
83 views

Does symlinking from Drive A to Drive B affect I/O on Drive A?

I was wondering if IO through a symbolic link affects IO on the host drive even if it points to a seperate drive? My setup is, /dev/sdb2 1.8T 443G 1.3T 26% /home1 /dev/sda3 1.8T 1.7T ...
11
votes
1answer
954 views

Is disabling barriers for ext4 safe on a laptop with battery?

The manual page says about the barrier option for ext4: Write barriers enforce proper on-disk ordering of journal commits, making volatile disk write caches safe to use, at some performance ...
3
votes
1answer
1k views

What's faster, dd 1.5TB or rsync 500GB?

I need to save data from a failing hard drive. Sounds like ddrescue or myrescue (or maybe clonezilla?) will be my best friends here, but I'm just wondering what will likely be faster: using ...
2
votes
2answers
422 views

vmstat IO stats: why the high bo during a download?

On my RHEL 4 machine, I was downloading a huge file (2.5GB)..I was checking the output of vmstat and was especially curious about seeing the disk IO using bi and bo. I know iostat is a better tool ...
4
votes
2answers
1k views

Hight iowait while the wMB/s is low

I was indexing a MySQL table. It makes a high load on that computer. It seems due to a high iowait. But it also shows that the wMB/s is only 2.87. Isn't even a common SATA HDD able to handle more ...
6
votes
5answers
2k views

Sync writes very slow. Ubuntu 10.10, 32 bits, ext4

I am running ActiveMQ on my Macbook Pro that runs Ubuntu 10.10, 32 bits with an ext4 partition. Linux iker-laptop 2.6.35-23-generic-pae #40-Ubuntu SMP Wed Nov 17 22:32:51 UTC 2010 i686 GNU/Linux If ...