4
votes
2answers
682 views

Why is dd using direct slower writing to disk than to a file

I am trying to compare aggregate write rates when writing to a file in a GPFS file system, as compared to writing directly to a disk on a system with Red Hat Enterprise Linux Server release 6.4 ...
2
votes
1answer
171 views

What is the most accurate way to measure disk read/write speed for an OpenVZ VPS host from within the host itself?

CentOS 6.x | OpenVZ I have an openvz VPS host and would like to measure disk read/write speed. Historically, on other physical systems, I've ran hdparm to collect this information. I haven't been ...
1
vote
2answers
70 views

Varing speed when reading sequentially from a HDD

I have just got a new HDD and I wanted to test the sequential read speed (the whole disk). I used: pv /dev/sda > /dev/null The disk is 500GB WD VelociRaptor (WD5000HHTZ). At the beginning the ...
3
votes
6answers
814 views

How can I defragment my SSD on linux?

This page demonstrates that defragmentation is beneficial for SSDs. I suppose this type of defragmentation has to be trim-aware, so as to preserve the life time of the disk. How can I do that on ...
3
votes
1answer
577 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
279 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
156 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 ...
13
votes
1answer
1k 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 ...
4
votes
1answer
2k 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
1k 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
2k 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 ...
7
votes
6answers
3k 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 ...