linux - Understanding metadata usage behavior in a newly converted btrfs filesystem

I have a 5 TB hard drive with 3.3 TiB (as reported by du) of media files in 119k files and directories; the average file size was about 28 MiB. I converted the ext4 partition into btrfs with btrfs-convert. The process took 10.4 hours and was CPU-bound. Right after the conversion:

# btrfs fi df /mnt/btrfs/
Data, single: total=3.03TiB, used=2.21TiB
System, single: total=32.00MiB, used=236.00KiB
Metadata, single: total=1.52TiB, used=1.10TiB

btrfs allocated all space on the hard drive (3.03 + 1.52 TiB ≈ 5 TB), and it apparently put ~1 TiB of file content into metadata chunks (1.10 TiB used). This is unexpected because very few of my files would fit into the leaf nodes.

The standard solution to the huge metadata allocation is to re-balance the metadata. btrfs balance start -m took 8.0 hours and was I/O-bound. Afterwards, it appears that btrfs not only released unused metadata chunks, but also moved file content from metadata chunks into data chunks.

# btrfs fi df /mnt/btrfs/
Data, single: total=3.32TiB, used=3.31TiB
System, single: total=32.00MiB, used=104.00KiB
Metadata, single: total=3.00GiB, used=2.18GiB

Could someone explain what is happening? Why would "metadata" consume 1.10 TiB initially, and why would balancing reduce it to 2.18 GiB? Does btrfs balance move file content from metadata chunks to data chunks?

I used Linux kernel 3.13.0-46. My files have no hard links, xattrs, SELinux contexts, nor ACLs. I have not turned on compression, and have not deleted the ext4 roll back image.

Comments

Use Google instead of Bing with Windows 10 search

I want to use Google Chrome and Google search instead of Bing when I search in Windows 10. Google Chrome is launched when I click on web, but it's Bing search. (My default search engine on Google and Edge is http://www.google.com ) I haven't found how to configure that. Someone can help me ? Answer There is no way to change the default in Cortana itself but you can redirect it in Chrome. You said that it opens the results in the Chrome browser but it used Bing search right? There's a Chrome extension now that will redirect Bing to Google, DuckDuckGo, or Yahoo , whichever you prefer. More information on that in the second link.

linux - Using an index to make grep faster?

I find myself grepping the same codebase over and over. While it works great, each command takes about 10 seconds, so I am thinking about ways to make it faster. So can grep use some sort of index? I understand an index probably won't help for complicated regexps, but I use mostly very simple patters. Does an indexer exist for this case? EDIT: I know about ctags and the like, but I would like to do full-text search. Answer what about cscope , does this match your shoes? Allows searching code for: all references to a symbol global definitions functions called by a function functions calling a function text string regular expression pattern a file files including a file

How do I transmit a single hexadecimal value serial data in PuTTY using an Alt code?

I am trying to sent a specific hexadecimal value across a serial COM port using PuTTY. Specifically, I want to send the hex codes 9C, B6, FC, and 8B. I have looked up the Alt codes for these and they are 156, 182, 252, and 139 respectively. However, whenever I input the Alt codes, a preceding hex value of C2 is sent before 9C, B6, and 8B so the values that are sent are C2 9C, C2 B6, and C2 8B. The value for FC is changed to C3 FC. Why are these values being placed before the hex value and why is FC being changed altogether? To me, it seems like there is a problem internally converting the Alt code to hex. Is there a way to directly input hex values without using Alt codes in PuTTY? Answer What you're seeing is just ordinary text character set conversion. As far as PuTTY is concerned, you are typing (and reading) text , not raw binary data, therefore it has to convert the text to bytes in whatever configured character set before sending it over the wire. In other words, when y...

linux - CentOs 7.1 - Install Tomcat 8

I am using this tutorial as a setup reference to getting a Tomcat 8 running on CentOs 7.1 , but after typing: [root@localhost tomcat]# sudo systemctl start tomcat I get the error: Job for tomcat.service failed. See 'systemctl status tomcat.service' and 'journalctl -xn' for details. systemctl status tomcat.service prints the following: [root@localhost tomcat]# systemctl status tomcat.service tomcat.service - Apache Tomcat Web Application Container Loaded: loaded (/etc/systemd/system/tomcat.service; disabled) Active: failed (Result: exit-code) since Wed 2015-11-25 16:54:33 CET; 1min 19s ago Process: 45873 ExecStart=/opt/tomcat/bin/startup.sh (code=exited, status=203/EXEC) Nov 25 16:54:33 localhost.localdomain systemd[1]: Starting Apache Tomcat Web Application Container... Nov 25 16:54:33 localhost.localdomain systemd[1]: tomcat.service: control process exited, code=exited status=203 Nov 25 16:54:33 localhost.localdomain systemd[1]: Failed to start Apache Tomcat Web App...

Notes

Search This Blog