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[News] Linux Kernel Space Tour: SCSI, Ext4

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Tour the Linux generic SCSI driver

,----[ Quote ]
| Computers control and transfer data to SCSI devices via SCSI commands. In 
| this article, the author introduces some of the SCSI commands and methods of 
| executing SCSI commands when using SCSI API in Linux®. He provides background 
| on the SCSI client/server model and the storage SCSI command. Next, he 
| explains the Linux generic SCSI driver API and offers an example of using a 
| system that focuses on executing the inquiry command using the generic 
| driver.      



,----[ Quote ]
| Ext4 is the evolution of the most used Linux filesystem, Ext3. In many ways, 
| Ext4 is a deeper improvement over Ext3 than Ext3 was over Ext2. Ext3 was 
| mostly about adding journaling to Ext2, but Ext4 modifies important data 
| structures of the filesystem such as the ones destined to store the file 
| data. The result is a filesystem with an improved design, better performance,  
| reliability and features.     


Fast ext4 fsck times, revisited 

,----[ Quote ]
| Last night I managed to finish up a rather satisfying improvement to ext4’s 
| inode and block allocators. The ext4’s original allocator was actually a bit 
| more simple-minded than ext3’s, in that it didn’t implement the Orlov 
| algorithm to spread out top-level directories for better filesystem aging. It 
| also was buggy in certain ways, where it would return ENOSPC even when there 
| were still plenty of inodes in the file system.     



Anatomy of ext4

,----[ Quote ]
| The fourth extended file system, or ext4, is the next generation of
| journaling file systems, retaining backward compatibility with the previous
| file system, ext3. Although ext4 is not currently the standard, it will be
| the next default file system for most Linux® distributions. Get to know ext4,
| and discover why it will be your new favorite file system.


ext4: The Fourth Extended Filesystem

,----[ Quote ]
| The ext4 file system is to be the successor to the ext3 journaled file system
| and will be available as an optional file system in the next release of
| Ubuntu, Ubuntu 9.04.
| The ext4 file system is now, as of December 25, 2008, released as stable and
| can be used as the dominant file system without fear of data lose…well, to be
| more clear I mean no more fear than any other “stable” file system.


Initial ext3 vs ext4 Results

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| We’ve started to do some internal benchmarking of ext3 vs ext4 at
| myYearbook.com to see if what we’ve seen and heard about ext4 was really
| true.  While the following benchmark is not in-depth, it does represent our
| initial findings, which match our anecdotal findings.  If all of these
| findings hold true, we expect them to have a large impact on our PostgreSQL
| OLTP workload where machines are IO bound.


Ext4 Filesystem Explained in Plain English

,----[ Quote ]
| If you need the advantages of Ext4, your existing Ext3 can be
| easily “upgraded” to Ext4 without the need to format. This means that all
| your data will stay intact once you upgrade (though I would highly recommend
| backing up).


Ext4 to be standard for Fedora 11, Btrfs also included

,----[ Quote ]
| According to current plans, version 11 of Fedora, which is expected to arrive
| in late May, will use Ext4 as its standard file system. That's what the
| Fedora Engineering Steering Committee (FESCo) recently decided, following a
| heated discussion in an IRC meeting. If however Ext3's successor encounters
| big problems with the pre-release versions of Fedora 11, the developers will
| dump that plan and revert to Ext3.


Ubuntu 9.04 Receives EXT4 Support

,----[ Qoute ]
| With the EXT4 file-system having been stabilized with the Linux 2.6.28
| kernel, the Ubuntu developers are preparing to adopt this evolutionary Linux
| file-system update. EXT4 will not replace EXT3 as the default file-system
| until at least Ubuntu 9.10, but as of yesterday, Ubuntu 9.04 now has
| install-time support for EXT4. In this article we are looking at the EXT4
| support within Ubuntu as well as providing a few Linux file-system benchmarks
| from a netbook-embedded solid-state drive. In this article we have published
| Ubuntu benchmarks of EXT4, EXT3, XFS, JFS, and ReiserFS file-systems.


Real World Benchmarks Of The EXT4 File-System

,----[ Quote ]
| In Nexuiz, World of Padman, and Unreal Tournament 2004 to represent gaming on
| the Linux operating system, the results were virtually identical. To the
| Linux gamer, switching to EXT4 or XFS will not really mean much in the way of
| improved frame-rates. If though you deal with compressing files often, of the
| four file-systems tested, the best appears to be EXT4 or XFS. When it came to
| multimedia encoding, we cannot call a decisive winner. In our GnuPG
| encryption test, EXT3 was the fastest followed by XFS. However, in the Bork
| encryption test, EXT4 was the fastest followed by EXT3. EXT3 does still
| appear to have some advantages.


Kernel: Ext 4 Filesystem Moves Beyond Developer Status

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| Theodore Ts'o has renamed the Ext4 filesystem, for which he has been
| responsible for source and documentation, from extdev to ext4. Linus Torvalds
| has also incorporated the change into his personal source tree for the
| upcoming Kernel 2.6.28.
| After the release of Kernel 2.6.27, a usual two-week merge window occurs when
| Torvalds merges the code for the next version into his personal kernel
| archive.


Ext4 is now the primary filesystem on my laptop

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| Over the weekend, I converted my laptop to use the ext4 filesystem.  So far
| so good!  So far I’ve found one bug as a result of my using ext4 in
| production (if delayed allocation is enabled, i_blocks doesn’t get updated
| until the block allocation takes place, so files can appear to have 0k
| blocksize right after they are created, which is confusing/unfortunate), but
| nothing super serious yet.  I will be doing backups a bit more frequently
| until I’m absolutely sure things are rock solid, though!


ext4 Implementation

,----[ Quote ]
| One major feature present in Fedora 9 will be the ext4 implementation. The
| new filesystem will not be the default for the distro, but will be available
| for users and systems administrators to enable. New functionality includes
| larger capacities and online defragmentation, for better performance and more
| reliability. To find out more, we talked with Eric Sandeen, Fedora project
| member and filesystem developer at Red Hat.



A better ext4 filesystem for Linux

,----[ Quote
| A new Linux filesystem gets rid of the 256-petabyte limit, and adds a
| checksum feature for the journal. But developers want you to know that it's
| not yet ready for production sytems.


ext4 2.6.25 Merge Plans

,----[ Quote ]
| "The following patches have been in the -mm tree for a while, and I plan to
| push them to Linus when the 2.6.25 merge window opens," began Theodore Ts'o,
| offering the patches for review before they are merged.


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.


First benchmarks of the ext4 file system

,----[ Quote ]
| The ext4 file system promises improved data integrity
| and performance, together with less limitations, and is
| definitely the step in the right way. Even if there are
| some regressions in our measurements, when compared to
| ext3, they're quite small and no doubt will be fixed
| before the development is finished. On the other hand,
| under some workloads ext4 is already showing much better
| results.

Version: GnuPG v1.4.9 (GNU/Linux)


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