Ext2
• Ext2
stands for second extended file system.
• It was
introduced in 1993. Developed by Rémy Card.
• This was
developed to overcome the limitation of the original ext file system.
• Ext2 does
not have journaling feature.
• On flash
drives, usb drives, ext2 is recommended, as it doesn’t need to do the over head
of
journaling.
• Maximum
individual file size can be from 16 GB to 2 TB
• Overall
ext2 file system size can be from 2 TB to 32 TB
How to create an ext2 filesystem
# mke2fs /dev/sda1
Ext3
• Ext3
stands for third extended file system.
• It was
introduced in 2001. Developed by Stephen Tweedie.
• Starting
from Linux Kernel 2.4.15 ext3 was available.
• The main
benefit of ext3 is that it allows journaling.
• Journaling
has a dedicated area in the file system, where all the changes are tracked.
When
the system crashes, the possibility of file system corruption is less
because of journaling.
• Maximum
individual file size can be from 16 GB to 2 TB
• Overall
ext3 file system size can be from 2 TB to 32 TB
• There are
three types of journaling available in ext3 file system.
o Journal –
Metadata and content are saved in the journal.
o Ordered –
Only metadata is saved in the journal. Metadata are journaled only after
writing
the content to disk. This is the default.
o Writeback
– Only metadata is saved in the journal. Metadata might be journaled either
before or after the content is written to the disk.
• You can
convert a ext2 file system to ext3 file system directly (without
backup/restore).
How to create ext3 file system :-
# mkfs.ext3 /dev/sda1
(or)
# mke2fs –j /dev/sda1
( -j for adding journaling capability )
How to convert ext2 to ext3 :-
# umount /dev/sda2
# tune2fs -j /dev/sda2
# mount /dev/sda2
/var
Ext4
• Ext4
stands for fourth extended file system.
• It was
introduced in 2008.
• Starting
from Linux Kernel 2.6.19 ext4 was available.
• Supports
huge individual file size and overall file system size.
• Maximum
individual file size can be from 16 GB to 16 TB
• Overall
maximum ext4 file system size is 1 EB (exabyte). 1 EB = 1024 PB (petabyte).
1
PB = 1024 TB (terabyte).
• Directory
can contain a maximum of 64,000 subdirectories (as opposed to 32,000 in ext3)
• You can
also mount an existing ext3 fs as ext4 fs (without having to upgrade it).
• Several
other new features are introduced in ext4: multiblock allocation, delayed
allocation,
journal checksum. fast fsck, etc. All you need to know is that
these new features have
improved the performance and reliability of the
filesystem when compared to ext3.
• In ext4,
you also have the option of turning the journaling feature “off”.
Creating ext4 file system :-
# mkfs.ext4 /dev/sda1
(or)
# mke2fs -t ext4 /dev/sda1
Converting ext3 to ext4
( Warning :- Never try this live or production servers )
# umount /dev/sda2
# tune2fs -O extents,uninit_bg,dir_index /dev/sda2
# e2fsck -pf /dev/sda2
# mount /dev/sda2 /var
Find your servers filesystem type
We can find the filesystem type used in our servers using
any one of the following commands
# mount
/dev/sda3 on / type ext3 (rw)
proc on /proc type proc (rw)
/dev/sda1 on /boot type ext3 (rw)
tmpfs on /dev/shm type tmpfs (rw)
# file -sL /dev/sda1
/dev/sda1: Linux rev 1.0 ext3 filesystem data (needs journal
recovery)
# df -T | awk ‘{print $1,$2,$7}’ | grep “^/dev”
/dev/sda3 ext3 /
/dev/sda1 ext3 /boot
XFS
XFS is a high-performance file system which was designed by
SGI for their IRIX platform.
Since XFS was ported to the Linux kernel in 2001,
XFS has remained a preferred choice for many enterprise systems especially with
massive amount of data.
XFS is a high performance filesystem,due to its high performance, architectural scalability
and robustness. For example, RHEL/CentOS 7 and Oracle Linux have adopted XFS as
their default file system, and SUSE/openSUSE have long been an avid supporter
of XFS.
XFS has a number of unique features that make it stand out
among the file system crowd, such as scalable/parallel I/O, journaling for
metadata operations, online de-fragmentation, suspend/resume I/O, delayed
allocation for performance, etc.
If you want to create and mount an XFS file system on your
Linux platform, here is how to do it.
XFS is packed full of cool features like
- guaranteed rate I/O
- online resizing
- built-in quota enforcement
- it can theoretically support filesystems up to 8 exabytes in size.
It’s been used on Linux since
about 2001, and is available as an install option on many popular Linux
distributions. With variable block sizes, you can tune your system like a
sliding scale to tweak for space efficiency or read performance. Best for
extremely large file systems, large files, and lots of files Journaled (an
asymmetric parallel cluster file system version is also available) POSIX
extended access controls The XFS file system is Open Source and included in
major Linux distributions. It originated from SGI (Irix) and was designed
specifically for large files and large volume scalability. Video and
multi-media files are best handled by this file system. Scaling to petabyte
volumes, it also handles great deals of data. It is one of the few filesystems
on Linux which supports Data Migration (SGI contributed the Hierarchical
Storage Management interfaces into the Linux Kernel a number of years ago). SGI
also offers a closed source cluster parallel version of XFS called cXFS which
like cVxFS is an asymmetrical model. It has the unique feature, however, that
it’s slave nodes can run on Unix, Linux and Windows, making it a cross platform
file system. Its master node must run on SGI hardware. Recommended Use: If you
really like to tweak your system to meet your needs, XFS is a great way to go.
The XFS file system is an extension of the extent file
system .XFS is a high performance 64 bit journaling file system .Support of XFS was merged into the linux kernel in around 2002 and In 2009
Red Hat Enterprise Linux version 5.4 usage of XFS file system .
Default file system in RHEL7 is XFS
XFS supports maximum file system size of 8 exbibytes for 64
bit file system .Some comparison of XFS file system is XFS file system cannot
be shrunk and poor performance with deletions of large numbers of files.
32-bit system 64-bit system
File size: 16 Terabytes 16 Exabytes
File system: 16 Terabytes 18 Exabytes
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