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[News] A Closer Look at Linux Filesystems

  • Subject: [News] A Closer Look at Linux Filesystems
  • From: Roy Schestowitz <newsgroups@xxxxxxxxxxxxxxx>
  • Date: Sun, 02 Sep 2007 05:09:54 +0100
  • Newsgroups: comp.os.linux.advocacy
  • Organization: Netscape / schestowitz.com
  • User-agent: KNode/0.10.4
Delve deep into drives

,----[ Quote ]
| Prabhakaran then goes on tracking bugs in all UNIX drivers, describing 
| inconsistencies and danger points, tracing the outline of a tougher file 
| system and then describing how to create an evolved file system that would 
| unite the advantages of most current file systems and overcome most of their 
| shortcomings. At the same time, he tries to describe how moving critical 
| logical pieces from the driver to the kernel (and therefore sharing this code 
| from one file system driver to the other) may make development easier and 
| faster while at the same time strengthening existing FS.       



ZFS, XFS, EXT4 Filesystems Compared

,----[ Quote ]
| EXT4 is fast for metadata operations, tar, untar, cpio, and postmark. EXT4 is 
| much faster than the others under FFSB. EXT4 with hardware RAID and external 
| journal device is ludicrously fast. EXT4 seems to have a bad interaction with 
| software RAID, probably because mkfs fails to query the RAID layout when 
| setting the filesystem parameters.    
| ZFS has excellent performance on metadata tests. ZFS has very bad sequential 
| transfer with hardware RAID and appalling sequential transfer with software 
| RAID. ZFS can copy the linux kernel source code in only 3 seconds! ZFS has 
| equal latency for read and write requests under mixed loads, which is good.   
| XFS has good sequential transfer under Bonnie++. Oddly XFS has better 
| sequential reads when using an external journal, which makes little sense. Is  
| noatime broken on XFS? XFS is very slow on all the metadata tests. XFS takes 
| the RAID layout into consideration and it performs well on randomio with 
| hardware or software RAID.    


OpenSolaris ZFS vs. Linux ext3 RAID5

,----[ Quote ]
| Few overarching conclusions can be drawn from the limited results of this
| study. Certainly, there are situations in which the Solaris/RAID-Z
| configuration appears to outperform the Ubuntu/RAID-5 configuration. Many
| questions remain regarding the large discrepancy in CPU usage for small-file
| operations. Likewise, the Ubuntu/RAID-5 configuration appears to perform
| slightly better in certain situations, though not overwhelmingly so. At best,
| under these default configurations, one can say that overall the Solaris
| configuration performs no worse, and indicates that it might perform better
| under live operating conditions. The latter, though, is largely speculation.


Why so many filesystems for Linux? What's the difference?

,----[ Quote ]
|     * EXT3       
|         * Most popular Linux file system, limited scalability in size and 
|         number of files       
|         * Journaled       
|         * POSIX extended access control
|     EXT3
|     file system is a journaled file system that has the greatest use in
|     Linux today. It is the "Linux" File system. It is quite robust and
|     quick, although it does not scale well to large volumes nor a great
|     number of files. Recently a scalability feature was added called
|     htrees, which significantly improved EXT3's scalability.
| [...]
|     * FAT32       
|         * Most limited file system, but most ubiquitous       
|         * Not Journaled       
|         * No access controls
|     FAT32
|     is the crudest of the file systems listed. Its popularity is with its
|     widespread use and popularity in the Windows desktop world and that it
|     has made its way into being the file system in flash RAM devices
|     (digital cameras, USB memory sticks, etc.). It has no built in security
|     access control, so is small and works well in these portable and
|     embedded applications. It scales the least of the file systems listed.
|     Most systems have FAT32 compatibility support due to its ubiquity.


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