2
votes
4answers
284 views

Why is writing so slow on raw device, and so fast on filesystem (USB key)?

I have a USB key that I am trying to benchmark quick'n'dirty on Linux. I'm testing write bandwith. dd on raw partition I created a partition starting at sector 2048, then did a 4 GB sequential ...
4
votes
2answers
764 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 ...
6
votes
1answer
417 views

Determining LVM Extent numbers for given file

I'm currently engaged in a non-work related homework exercise. I have an ext4 filesystem sitting on a logical volume. I'm testing different performance tuning strategies and this idea occurred to me. ...
4
votes
2answers
590 views

Is there any performance penalty to having multiple segments for one volume in LVM?

We have a big drive that we've split up using LVM. We allocated one segment to the root filesystem and several other segments to other filesystems. Then we wanted to add more space to the root ...
4
votes
2answers
874 views

Does the filesystem influence flash drive speed?

I'm currently filling up an empty 16GB flash drive which gives me a lot of time for imponderables. It's formatted as fat32 or whatever it came with (and I'll probably leave it that way for ease of ...
1
vote
0answers
215 views

Connected external HDD slows down system

I need to connect large external hard disks (with many many files) to a system running Ubuntu. I have no idea how the Linux kernel is treating the inodes for the external drives, but attaching huge ...
42
votes
5answers
21k views

Can I configure my Linux system for more aggressive file system caching?

I am neither concerned about RAM usage (as I've got enough) nor about losing data in case of an accidental shut-down (as my power is backed, the system is reliable and the data are not critical). But ...
16
votes
3answers
13k views

What is the most high-performance Linux filesystem for storing a lot of small files (HDD, not SSD)?

I have a directory tree that contains many small files, and a small number of larger files. The average size of a file is about 1 kilobyte. There are 210158 files and directories in the tree (this ...
24
votes
1answer
2k views

Why does “ls *” take so much longer than “ls”?

I have a couple of files in a directory: $ ls | wc -l 9376 Can anybody explain why there is such a huge time difference in using ls * and ls? $ time ls > /dev/null real 0m0.118s user ...
4
votes
1answer
1k views

How can we customize linux file systems like ext2/3?

Actually IOzone is a filesystem benchmark tool. The benchmark generates and measures a variety of file operations like sequential reading/writing, random reading/writing. So I want to customize my own ...
6
votes
2answers
755 views

I/O-overhead of dm-encrypted device?

What would be the Read-/Write-overhead when using dm-crypt (LUKS) as full disk-encryption (including root partition) on a Linux-Desktop (Ubuntu)? I plan to stack it like so: LUKS > LVM > ext4 The CPU ...