Should i use ext4 or ext3

You have mentioned it as 64, but its actually 6,40, 6 lakhs 40 thousands. I just tested by increasing the condition value in my script to , and it did created all the sub-directories. All your documentation on linux are so helpful. I was wondering, if you could provide some documentation on linux servers hardening centos latest version. EXT4 already has 48 bit block addressing. Whoever took their time to compile this, deserves a pat on the back. Well Done. I have been looking out for a reliable home-NAS.

Much of my folder structure is nested in folders which makes sense from a filing perspective , but not in a backup system. I have been looking at the Synology set of NAS systems. Really a Very Nice documents Specially when a beginner like me want to know difference between all the file systems in Linux. Thank you. PS if any one use android x86 i suggest use ext2 or 3 format because ntfs and fat32 suck at android compitablity. If I have a kernel version older than 2.

Do I need to patch my kernel or a complete kernel upgrade is needed. So use. Save my name, email, and website in this browser for the next time I comment. Notify me of followup comments via e-mail. All rights reserved Terms of Service. This article explains the following: High level difference between these filesystems. How to create these filesystems. How to convert from one filesystem type to another.

However, ext4 uses delayed allocation, which allows it to coalesce writes and make better decisions about how to allocate blocks for the writes it has not yet committed.

When pre-allocating disk space for a file, most file systems must write zeroes to the blocks for that file on creation. Ext4 allows the use of fallocate instead, which guarantees the availability of the space and attempts to find contiguous space for it without first needing to write to it.

This significantly increases performance in both writes and future reads of the written data for streaming and database applications. This is a chewy—and contentious—feature. Delayed allocation allows ext4 to wait to allocate the actual blocks it will write data to until it's ready to commit that data to disk. By contrast, ext3 would allocate blocks immediately, even while the data was still flowing into a write cache.

Delaying allocation of blocks as data accumulates in cache allows the filesystem to make saner choices about how to allocate those blocks, reducing fragmentation write and, later, read and increasing performance significantly.

Unfortunately, it increases the potential for data loss in programs that have not been specifically written to call fsync when the programmer wants to ensure data has been flushed entirely to disk. With legacy filesystems, close fd ; is sufficient to guarantee that the contents of file will be flushed to disk.

Even though the write is not, strictly speaking, transactional, there's very little risk of losing the data if a crash occurs after the file is closed. If the write does not succeed due to errors in the program, errors on the disk, power loss, etc. If other processes access the file as it is being written, they will see a corrupted version. And if other processes have the file open and do not expect its contents to change—e.

Instead, they might write to a new file, close it, then rename it over the old one:. Under filesystems without delayed allocation, this is sufficient to avoid the potential corruption and crash problems outlined above: Since rename is an atomic operation, it won't be interrupted by a crash; and running programs will continue to reference the old, now unlinked version of file for as long as they have an open filehandle to it.

But because ext4's delayed allocation can cause writes to be delayed and re-ordered, the rename "newfile","file" may be carried out before the contents of newfile are actually written to disk, which opens the problem of parallel processes getting bad versions of file all over again.

To mitigate this, the Linux kernel since version 2. This reduces, but does not prevent, the potential for data loss—and it doesn't help at all with new files. If you're a developer, please take note: The only way to guarantee data is written to disk immediately is to call fsync appropriately.

Ext3 was limited to a total of 32, subdirectories; ext4 allows an unlimited number. Beginning with kernel 2. Ext3 did not checksum its journals, which presented problems for disk or controller devices with caches of their own, outside the kernel's direct control. If a controller or a disk with its own cache did writes out of order, it could break ext3's journaling transaction order, potentially corrupting files being written to during or for some time preceding a crash.

In practice, it's been discovered that storage devices and controllers frequently do not honor write barriers—improving performance and benchmarks, where they're compared to their competitors but opening up the possibility of data corruption that should have been prevented.

Checksumming the journal allows the filesystem to realize that some of its entries are invalid or out-of-order on the first mount after a crash. This thereby avoids the mistake of rolling back partial or out-of-order journal entries and further damaging the filesystem—even if the storage devices lie and don't honor barriers. Under ext3, the entire filesystem—including deleted and empty files—required checking when fsck is invoked.

By contrast, ext4 marks unallocated blocks and sections of the inode table as such, allowing fsck to skip them entirely. This greatly reduces the time to run fsck on most filesystems and has been implemented since kernel 2. Ext3 offered timestamps granular to one second. While sufficient for most uses, mission-critical applications are frequently looking for much, much tighter time control.

Ext4 makes itself available to those enterprise, scientific, and mission-critical applications by offering timestamps in the nanoseconds. Ext3 filesystems also did not provide sufficient bits to store dates beyond January 18, Ext4 adds an additional two bits here, extending the Unix epoch another years.

If you're reading this in AD, you have hopefully already moved onto a better filesystem—but it'll make me posthumously very, very happy if you're still measuring the time since UTC , January 1, Neither ext2 nor ext3 directly supported online defragmentation—that is, defragging the filesystem while mounted. Ext2 had an included utility, e2defrag , that did what the name implies—but it needed to be run offline while the filesystem was not mounted.

This is, obviously, especially problematic for a root filesystem. The situation was even worse in ext3—although ext3 was much less likely to suffer from severe fragmentation than ext2 was, running e2defrag against an ext3 filesystem could result in catastrophic corruption and data loss.

Although ext3 was originally deemed "unaffected by fragmentation," processes that employ massively parallel write processes to the same file e. Several userspace hacks and workarounds, such as Shake , addressed this in one way or another—but they were slower and in various ways less satisfactory than a true, filesystem-aware, kernel-level defrag process.

Ext4 addresses this problem head on with e4defrag , an online, kernel-mode, filesystem-aware, block-and-extent-level defragmentation utility. Ext4 is, as the Monty Python plague victim once said, "not quite dead yet!

There are still a few key features being developed into future versions of ext4, including metadata checksumming, first-class quota support, and large allocation blocks. Since ext4 has redundant superblocks, checksumming the metadata within them offers the filesystem a way to figure out for itself whether the primary superblock is corrupt and needs to use an alternate.

It is possible to recover from a corrupt superblock without checksumming—but the user would first need to realize that it was corrupt, and then try manually mounting the filesystem using an alternate. Since mounting a filesystem read-write with a corrupt primary superblock can, in some cases, cause further damage, this isn't a sufficient solution, even with a sufficiently experienced user!

See also Best answer: What are Unix components? Related posts: Your question: What is the most common Linux file system? What file system does Linux use? Frequent question: Which file system is best for Kali Linux? What is default file system in Linux? What is ext3 file system in Linux? See also What are groups in Ubuntu?

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