Performance Evaluation of the EXT4 File System

A Comparative Study Against EXT3, ReiserFS and JFS

Alireza Ghobadi1, Amir Hesam Yaribakht

1, Sanam Maham

2, Mohammad Hossein Ghods

2

1Faculty of Information Technology Multimedia University Cyberjaya 63000 Selangor, Malaysia

2SOHA Sdn. Bhd.,AB1 MSC Center, Cyberjaya, Selangor, Malaysia

Abstract— Base on several definition of File System, File

System is a system which is responsible to handle files and

managing data in any operating system [1]. According to

these definitions, choose a File System to managing data on

your system, is one of the consideration for anybody who use

a computer. Anybody can fill this problem when you have a

lot of files with a large portion. File System types can be

classified into disk File Systems, network File Systems and

special purpose File Systems[2][3][4.] The purpose of this

Paper is “comparison Performance evaluation among four

File Systems”. According to above goals, there are several

file systems on Linux operation system. These file system are

EXT2, EXT3, EXT4, ReiserFS, JFS, and etc. In this paper, we

are neither define several file systems on Linux nor compare

them and tested by IOzone and Postmark benchmark tools

[5][6]. The performance result has shown base on read, re-

read, write and re-write of file for IOzone benchmark tool

and create, read, append, delete for Postmark benchmark

tool. We have chosen IOzone bench mark for our experiments

as it is preferred for operating system evaluation [7].

Keywords- Performance Evaluation, File System, EXT4,

EXT3, ReiserFS

1 Introduction

Base on several definition of file system, File system is a

system which is responsible to handle files and managing data

in any operating system [1]. According to these definitions,

choose a good file system with the best performance is one of

the considerations [1].

File system types can be classified into disk, network

and special purpose. A disk file system designed for the file

storage on a data storage device. Normally disk drive, directly

or indirectly connected to the computer or any computer

device.

The principal aims of file system are to address

scalability, performance, reliability, capabilities and

robustness. On the other hand, the most popular Linux file

system due to its reliability, rich feature set, relatively good

performance, and strong compatibility between versions of

file system.

According to above goals, there is several file system on

Linux operating system. These file system are EXT2, EXT3,

EXT4, ReiserFS, JFS, and etc [7][8][9][10][11][12].

In this paper, we are neither define several operating

systems on Linux nor compare them and tested by IOzone

and Postmark benchmark tools. We will be showing

performance of them based on read, re-read, write and re-

write of file.

We have chosen IOzone and Postmark benchmark tools for

our experiments as it is preferred for operating system

evaluation [13][14].

1.1 Instructions for authors

This paper, compares and evaluates EXT4 against EXT3

and ReiserFS, JFS file systems on Linux. The paper studies on

these four file system in section 2, 3, 4. Related work in

section 5. Then, it focuses on performance evaluation tools in

section 6. Implementation of benchmark tools in section 7.

Results and discussion in section 8, and finally, conclusion

and future work in section 9.

2 Extent file systems

Extent file system was earlier file system that developed

on Linux by Rmy Card, Laboratoire. Until now Extended has

four generations and implement on several version of Linux

[10].

EXT2 designed by Wayne Davidson and Stephen

Tweedie and Theodore. They extended from EXT file system

which designed byRemy Card and implement on the standard

Linux file system [15][16].

EXT3 is one of the traditional Unix-derived file systems.

it used a indirect block mapping scheme to keep track of each

block. It the same data structures and supports journaling.

EXT3, which just added some features to EXT2 while

keeping the on-line format and approach of EXT2 [9].

EXT4 was developed by Theodore Ts’o, who was, at the

time In 2006. The uber Linux developer, which developed the

EXT3 maintainer, began work on EXT4., EXT4 changed a

deep code change and the data structures. These changes used

to make a better file system, faster, reliable, more features,

and better code. The most important and hard working on

EXT4, added new features such as, Extents, journaling check

summing, block allocation, delayed allocation, faster fsck, on-

line defragmentation, and larger directory sizes (up to 64,000

files) [12].

3 ReiserFS

ReiserFS was developed as a part of the standard Linux

kernel by Hans Reiser. [2] It is available on the most version

of Linux operating system. ReiserFS supports metadata

journaling. The ReiserFS has excellent performance for small-

files. ReiserFS Developed based on B* Balanced Trees to

organize directories, files, and data. B* provides fast directory

lookups and fast deletes operations. Other performance

features include support for sparse files and dynamic disk

inode allocation [2].

4 Journalin File Systems (JFS)

JFS introduced by IBM as UNIX file system with the initial

release of AIX Version 3.1. It has now introduced a second

file system that is to run on AIX systems called Enhanced

Journal File System (JFS2). JFS2 is available in AIX Version

5.0. The JFS Open Source code on originated [17].

JFS is modified primarily for the high throughput and

reliability requirements of servers. JFS uses extent-based

addressing structures, along with clustered block allocation

policies. It is make compact, efficient, and scalable structures

for mapping logical offsets within files to physical addresses

on disk. An extent is a sequence of contiguous blocks

allocated to a file as a unit. The addressing structure is a

B+Tree populated with extent descriptors, rooted in I-node

and keyed by logical offset within the file [17].

JFS supports block sizes of 512, 1024, 2048, and 4096

bytes on a per-file system basis. Smaller block sizes reduce the

amount of internal fragmentation. However, small blocks can

increase path length since block allocation activities may

occur more often than if a large block size was used. The

default block size is 4096 bytes [18].

JFS supports both sparse (which allow data to be written to

random locations within a file without instantiating others

unwritten file blocks.) and dense files, on a per-file system

basis. [18]

5 Related Work

Some researcher studied on Extents file

systems.[12][13][14] Avantika Mathur have worked on EXT3.

The purpose of their research was to provide branch of EXT4

from EXT3.[4] They compared EXT3, EXT4; XFS file

systems with three tools as FFSB, IOzone and Postmark. With

FFSB tool they test these file systems base on throughput

(MB/Sec) and CPU percent usage. [13] [14]

This test has shown that XFS has higher throughput

(MB/Sec) than EXT3 and EXT4, but it has lower CPU percent

usage than EXT3 and EXT4. EXT4 has higher throughput

(MB/Sec) performance than EXT3, but it has lower CPU

percent usage than EXT3 [9]. By IOzone tool they test these

file systems base of six operations as write, re-write, read, re-

read, random write and random read [11]. In this test shows

that in Write, re-write, random write and random read, EXT4

has higher throughput (KB/Sec) performance than XFS and in

general EXT4 has higher throughput (KB/Sec) performance in

all six operations than EXT3[9].

The test also shows that in read and re-read operations XFS

has higher throughput (KB/Sec) performance than EXT3 and

EXT4. Also observe that in re-write, random write, random

read, XFS has higher throughput (KB/Sec) performance than

EXT3. In write operation EXT3 has higher throughput

(KB/Sec) performance than XFS. With Postmark tool they test

these file systems based on two operations as read and write.

The test result not only shows that EXT4 has higher

throughput (MB/Sec) performance than EXT3 and XFS, but

also EXT3 has higher throughput (MB/Sec) performance than

XFS. In their comparison they find that EXT4 has a good

improvement of EXT3 and has become an enterprise-ready

solution, with a good balance of scalability, reliability,

performance and stability. [2]

Other researcher named, Ricardo Galli works on journal file

systems available for Linux as EXT3, ReiserFS, XFS and JFS

and they introduce to the basic concepts of file systems,

buffer-cache, and page-cache carried out in the Linux kernel.

[17]Their performance result shows that XFS, ReiserFS and

EXT3 have demonstrated that they are excellent and reliable

file systems. In this research, they achieved (i) EXT3 is going

to be the standard file system for Linux operating system,

specially Red Hat, (ii) JFS is a valid alternative for migrating

AIX and OS/2 installation to Linux.

(iii) In all journal file systems, ReiserFS is the only file

system which has standard Linux tree since 2.4.1 which SuSE

supports it. (iv) XFS is being used in large servers (especially

in the Hollywood industry). It is due mainly to the influence of

SGI market. (v) JFS has gotten the worst results (when tested

by any benchmarks) not only on performance, but also for

stability issue in the Linux port.

Dr. Oliver Diedrich has a well done study on EXT3 and

EXT4 file systems. He compares the structure of EXT3 and

EXT4 file systems base on large volumes, huge files and

extent trees. He evaluates a performance of these two file

systems based on creation (based on time and write speed) and

deletion (based on time) of eight 1 GB files and 10000

random read and write operations in 8 GB. He did not mention

what tools he used in his test, the performance with large files

between EXT3 and EXT4. The tests shows that in creation of

eight 1 GB files, time in EXT4 improved 6.9% and write

speed also improved 7.0% than EXT3. In deletion of eight 1

GB files, time improved 97.2% than EXT3. And among

10000 random read and write operations in 8 GB, EXT4

improved 10.9% than EXT3[11].

6 Performance Evaluation Tools

Benchmark is a tool for performance evaluation. There are

several benchmarks for file system available [13]

IOzone is one of the famous benchmark tools on file

system to generate and measures a selection of file operations.

It has been runs for test many operating systems. The IOzone

tests file I/O performance. I/O performance tests based on

Read, re-read, read backwards, read strided, write, re-write,

fread, fwrite, random read/write, pread/pwrite variants,

aio_read, aio_write, mmap.It is useful for file system analysis

of a vendor’s computer platform. [13]

Another famous benchmark is The Postmark. It is

responsible to creating a massive bulk of alternatively

modifying files and calculating the transaction rates for a

workload approximating a large Internet electronic mail server

[14]. Postmark operation, produces random text files. The text

files size categorizes from low bound to high bound. The size

is configurable between low and high bound The text file pool

is of configurable size and can be located on any accessible

file system.[14] Once the bulk has been created consists of a

pair of smaller transactions (i) Create file or Delete file and

(ii) Read file or Append file operation.

According to comparison of these benchmark tools, the

achievement the IOzone performance shows that, this tool is

more suitable for experimental result due to the performance

of IOzone is higher than Postmark tool.

7 Implementation

File system benchmarking requires careful setup. An issue

one must often contend with is how to defeat the effects of the

file system buffer cache. Without careful experimental design,

all of the file system requests could be satisfied in the cache

and no disk activity would occur. A usual way to avoid this

problem is to use a total file size that exceeds the amount of

main memory available on the system.

Another approach is to use a file-access mode that bypasses

the file system buffer cache, such as O_DIRECT. We chose to

not use O_DIRECT for this paper

The second issue that one must address is estimating the

accuracy of the results of the test. In our experience, file

system benchmarks are notorious for being non repeatable,

bimodal, and full of hysteresis effects, making it a challenge to

get consistent results.

In this paper we have IOzone and Postmark benchmarks

using below system:

The small system that is Intel(R) processor Core(TM)

Duo 2.20 GHz with 4GB of memory and a 320 GB SATA

disk. For the experiments of this paper, this machine was

booted with 4 GB of RAM.

Nowadays, mentioned machine provides a sampling used

to run Linux.

For using IOzone and Postmark benchmarks firstly we

should install them in the system.

Now searching is in process and gives the latest model of

the searched benchmark.

8 Results and Discussion

This section is a description of test result. Each graph defines

system’s structure.

8.1 IOzone result

Read graph shows that EXT4 has not good performance in

those file size less that 100 MB. EXT4 is Extent base

allocation. It is block allocation and it use contiguous

allocation to allocate the file in blocks of disk. Because of this

type of allocation, EXT4 has overhead and performance is not

good on small file. In other hand, small file size because it is

contiguous when file finish there are some space in the

contiguous file that still empty. The other reason is the

overhead for read the file system should refer to directory that

has file name. Address of file and length of the file and if the

file be small, this cause overhead happened. [13]

Allocation features use for large file size. Figure 4 shows

that the performance of EXT4 is higher than other file

systems. For the large file, EXT4’s performance is higher than

other file systems because of block allocation that fill the

contiguous block in disk.

EXT3 allocates blocks for a file one at a time (typically

using 4KB blocks). For very large files, the associated

function that doses the allocation will have to be called

thousands of times. EXT4 uses ―multi-block allocation‖. It

allows multiple blocks (hence the name) to be allocated during

one function call. This can greatly improve the performance of

EXT4 relative to EXT3, particularly for large files. [12]

JFS dynamically allocate space for disk I-nodes as

required, freeing the space when it is no longer needed. Two

different directory organizations are provided. (i) The first

organization is used for small directories and stores the

directory contents within the directory’s I-node. This

eliminates need for separate directory block I/O as well as

need to allocate separate storage. [18] By using directory’s I-

node can eliminate separate directory block I/O and allocate

separate storage. (ii) Organization is used for larger directories

and represents each directory as a B+Tree keyed on name. It

provides faster directory lookup, insertion, and deletion

capabilities.

Because of these reasons JFS in small file has better

performance than EXT4 but for file size from 100MB and

above JFS has lower performance than EXT4. [12]

ReiserFS uses B* Balanced Trees to organize directories,

files, and data. This provides fast directory lookups. [2] So it

has better performance on read operation in small file size

generally less and equal than 20MB file size.

First graph shows result base on read feature. Figure1

shows that experience by IOzone benchmark.

Figure 1: IOzone test for Read feature

According to above explanation, Figure1 shows that EXT4

has weakness in small file. Also this graph shows that

ReiserFS and EXT3 have a good performance with small file.

But with increasing file size, EXT4 performance increase as

well. Also this graph shows that JFS more stable than other

file system.

Figure 2: IOzone test for Re-Read feature

Figure2 shows that EXT3, ReiserFS, and JFS has a good

performance when file size is small. But with increasing file

size, JFS and EXT3 performance decrease slowly and EXT4

performance increase. Figure2 Shows with large file size JFS

has higher performance.

Figure3: IOzone test for Write feature

Figure3 shows write performance in these four file

system. Figure3 shows that EXT4 and JFS has a good

performance with small file size. ReiserFS has the lowest

performance. But with increasing file size the EXT4

performance is not change too much, but JFS performance

decreasing too much. In large file size JSF has the worst

performance.

Figure 4: IOzone test for Re-Write feature

Figure4 shows Re-write feature that tested by four file

system. For this feature, JFS has the best performance base on

small file size and large file size. This graph shows that EXT4

performance slowly increase and JFS performance deeply

decrease.

Figure5: All feature performance for small file size (1MB).

Figure6: All feature performance for large file size (100MB).

Figure 5 and Figure 6 shows other perspective of

performance of these four file system. With comparison four

feature performance in small file size; JFS has a good

performance in Re-Write, and Re-Read. Also the worth

performance in small file size belong to EXT4. Comparison

between EXT3 and EXT4 which are using extent, EXT3 is

much better than EXT4.

Also according to large file size, EXT4 mostly has a better

performance than others. Specially, on their write file. JFS

also has a good performance on read file.

Postmark result

According to postmark description, run postmark on four

file systems. (EXT4, JFS, EXT3, and ReiserFS) Postmark

used maximum create, read, append, and delete files base on

Table 1.

Table1: Four file systems comparison table with postmark.

Figure7 shows result of postmark testing. This graph shows

that EXT4 is the fastest file system in all of the execution part.

Also ReiserFS are in the second level.

Figure7: Postmark test result base on creation, append,

deletion, and read.

1. CONCLUSION AND FUTURE WORK

Choose a file system to managing data on your system, is

one of the consideration for anybody who use a computer.

Anybody can fill this problem when you have a lot of files

with a large portion [20].

This project define base on famous file system comparison

on Linux. Project starts which a research on file system on

Linux and then find some research on these file systems.

There is some evaluator tools look like FFSB, IOzone, and

Postmark. Benchmark which using IOZONE and

POSTMORK which is more famous. These tools are choosing

to check which one is more reliable for evaluation for my

project. Some of the Research objectives in this project are

carrying out as follow (i) Assess different type of FS on Linux

Assess different type of file system performance evaluator

tools (ii) Categorizes file system base in performance.

The result shows that EXT4 which is using extend have a

performance on large file size but it is not suitable for small

file size. In other word, with increase file size, the EXT4

performance increase. Other file systems (which is JFS and

using journaling) also has a good performance (especially in

write and Re-write file). But JFS is not update any more

during 2 years. EXT3 also has a reliable performance on small

file size.

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