When choosing a file system for Linux, two of the most popular options are ext4 and XFS. Both file systems have their own sets of advantages and use cases where they excel. In general, ext4 tends to be better for most everyday desktop and general purpose server workloads, while XFS shines in high performance environments.
Brief History of ext4 and XFS
Ext4 is a successor to the ext3 file system and was introduced in 2008. It aimed to improve upon ext3 by adding new features like extents, preallocation, delayed allocation, etc. Ext4 is the default file system on many Linux distributions today.
XFS on the other hand was developed by SGI in the 1990s for their IRIX operating system. It was designed for high performance environments and includes features like B+ tree indexing, extents, delayed allocation, etc. XFS has found usage in Linux for high throughput workloads like video editing, scientific computing, etc.
Major Differences
Here are some of the major differences between the two file systems:
Journaling
– Ext4 uses journaling to prevent data corruption in case of system crashes. It supports multiple journaling modes like writeback, ordered, and journal.
– XFS relies on metadata consistency to prevent corruption instead of journaling. This can improve performance but also risks higher corruption in event of crashes.
Extent-based Allocation
– Both XFS and ext4 use extents for allocation which improves contiguous storage allocation performance over traditional block mapping.
– Ext4 supports extent trees while XFS utilizes B+ trees for faster extent lookups.
Delayed Allocation
– Both file systems support delayed allocation which defers actual writing of data blocks until the time of sync or fsync. This optimization helps improve write speeds.
– XFS supports even more sophisticated delayed allocation techniques to optimize performance.
Compression
– Ext4 has support for transparent file compression using the LZ4 algorithm. This can help reduce storage space used.
– XFS does not support transparent filesystem compression currently.
Checksumming
– Ext4 supports checksumming of journal records to improve reliability and catch errors.
– XFS does not have similar checksumming capabilities.
Performance Comparison
Here is how ext4 and XFS compare in terms of performance for different workloads:
Throughput
– For sequential throughput with large files, XFS generally performs better than ext4 thanks to its advanced allocation algorithms.
– Ext4 shows comparative or better performance for random mixed workloads like databases, mail servers, file servers etc.
| Filesystem | Sequential Throughput | Random Mixed Throughput |
|---|---|---|
| XFS | Higher | Lower |
| ext4 | Lower | Higher |
Multithreaded Workload
– XFS parallelizes operations better and scales well under highly multithreaded workloads.
– Ext4 does not handle multithreaded writes as efficiently leading to loss of throughput.
Metadata Operations
– Operations like creating small files, lookups, deletions are faster on XFS thanks to faster metadata handling.
– Ext4 metadata performance is slower in comparison due to journal overhead.
Latency
– For workloads prone to fragmentation, XFS shows lower latency thanks to its extent-based allocation.
– Ext4 is prone to higher file fragmentation over time leading to higher latency.
Reliability
File system reliability is also an important criteria when comparing the two. Here is a summary:
Journaling
– The journaling implementation in ext4 provides better protection against corruption in event of crashes.
– XFS has higher risks of filesystem corruption since it does not employ journaling.
Checksumming
– Checksumming of journal records allow ext4 to catch errors better and improve reliability.
– XFS does not have checksumming capabilities currently.
Defragmentation
– Ext4 requires periodic defragmentation to maintain performance and prevent fragmentation.
– XFS is relatively resilient to fragmentation, so does not require defragmentation.
Recovery Time
– Ext4 generally has faster recovery time after crashes since the journal can replay recent transactions.
– XFS has to run full filesystem consistency checks on crash which takes longer.
Scalability
Both file systems are designed to scale well across modern storage systems:
Filesystem Size Limits
– Ext4 has a maximum filesystem size limit of 1 exbibyte.
– XFS has a higher limit of 8 exbibytes for filesystem size.
File Size Limits
– The maximum file size supported by ext4 is 16 tebibytes.
– XFS supports much higher maximum file sizes up to 8 exbibytes.
Number of Inodes
– Ext4 supports up to 4 billion inodes per filesystem.
– XFS supports a higher limit of over 9 quintillion inodes per filesystem.
So in summary, XFS generally scales better for extremely large storage deployments and large files. Ext4 scales sufficiently for most everyday use cases.
Use Cases
Given the differences in their designs, ext4 and XFS are each suited for these typical use cases:
Ext4 Use Cases
– General purpose filesystem for desktops, laptops
– Database servers like MySQL, PostgreSQL
– Mail servers like Exchange, Postfix
– Shared storage and file servers
– Boot partitions
XFS Use Cases
– File servers with high capacity and throughput needs
– Big data analytics, data warehousing servers
– High performance computing clusters
– Video editing and production storage
– Servers for virtualization like Xen, KVM
Conclusion
In conclusion, while XFS offers higher performance and scalability for I/O intensive workloads, ext4 provides a better overall balance for everyday desktop and server workloads.
The journaling and checksumming capabilities of ext4 also make it a more reliable choice for most general purpose use cases. It reduces risk of data corruption and speeds up crash recovery.
Ext4 is generally recommended as the default filesystem on Linux distributions due to its robustness. For high throughput media storage servers, scientific computing clusters, or big data analytics, XFS can deliver better performance.
So choose ext4 where reliability and resistance to fragmentation is preferred, and XFS where maximum speed and scalability is needed. Evaluate your use case and workload profiles before deciding between these two excellent Linux filesystem options.