2004.12_Window Writing-Ntfs for Linux.pdf

REVIEWS

Mounting NTFS

Window Writing

Writing to NTFS partitions with the

can check out the

results of all this effort

in the “Benefits for

Linux Magazine Read-

ers” box.

The install script also

moves the new kernel

module and a few other

bits and bobs into the

right places on your sys-

tem (more or less

smoothly, depending on

the distribution you

use). Finished! The

Linux kernel should

now load the module on

demand, typically when

you issue a command

like the following:

NTFS driver is actually quite danger-

ous. But help is at hand. Paragon has

an improved kernel module, and

there is always Captive, a GPL-

licensed program that uses a variety

of Windows drivers.

BY JAN KLEINERT

U p to now, the Linux kernel has

mount -t ufsd -o U

iocharset=utf8 U

device mountpoint

only supported read-only mount-

ing of NTFS partitions. Support

for write access is experimental, and

errors associated with the write process

could completely wipe out an NTFS par-

tition. Both Captive, a GPL licensed

program, and its commercial competitor

“NTFS for Linux 3” by Paragon [1] aim

to change that. Linux Magazine tested

the latter as one component in a larger

suite of tools in [2].

Captive, a GPL-licensed program, is

fairly new on the scene. Looking under

the hood of Captive reveals a fairly com-

plex structure comprised of a small

kernel module and a larger userspace

module. The userspace module’s claim

to fame is that it actually managed to

convince the native NTFS driver from

Windows XP to cooperate with Linux

(see Figure 1).

The iocharset parameter helps out with

character conversions in file and path

names, as shown in Figure 2. Of course,

you can’t expect the driver to decrypt

files that you have encrypted on NTFS,

but it will unpack compressed files.

Our first impression was that the mod-

ule is fairly quick; the long waits with

the previous version are definitely a

thing of the past. The last time we tested

the Paragon module, ls -l took about 44

seconds to complete for an NTFS direc-

tory with around 50 files; the current

version took about four seconds. Just to

compare: the read-only driver from the

Paragon Module for the

Linux Kernel

Some parts of the Paragon Linux driver

are open source, although the driver is

released under a proprietary license. In

addition to these components there are

two binary libraries, one for kernel 2.4,

and the other for 2.6. Users need not

worry about the complex infrastructure;

Admins just need to ensure that the right

distribution kernel header files are avail-

able and either run the install script or

build the tool using make .

If you have not already done so,

install.sh will create symlinks for the

kernel headers in /usr/include before

going on to compile and will link an

object file (the UFSD kernel module). We

originally had some trouble getting this

to work on our lab system, which runs

Suse 9.1. A quick check showed that the

kernel header had not been included

properly, and that a few linker errors

were occurring. Paragon had this sorted

out within a few days. By the way, you

NTFS for Linux 3

Manufacturer: Paragon Software Group

Internet:

http://www.ntfs-linux.com

Captive 1.1.5

License:

Proprietary, US$ / EUR

69.95. Discount available

for Linux Magazine readers,

see box “Benefits for Linux

Magazine Readers”, Educa-

tional licenses on request.

Author: Jan Kratochvil

Internet: http://www.jankratochvil.net/

project/captive

License: GPL, but requires a few Windows

files

December 2004

www.linux-magazine.com

Paragon NTFS for Linux 3 versus Captive 1.1.5

Mounting NTFS

REVIEWS

Linux kernel displayed the

shell prompt after about

three seconds.

should come as no sur-

prise.

Measuring Write

Performance

Both of these tools were

designed with writing to

NTFS partitions in mind.

And that makes measuring

the data throughput for

read operations really

interesting. The “Test Pro-

cedure” box goes into the

gory details of the read

tests. The Paragon soft-

ware demonstrated better

performance in this disci-

pline, bundling the test file

off to the Windows parti-

tion in a time of one

minute and 10.5 seconds –

this is equivalent to a

throughput of 3.75 MB/s.

In contrast to this, Cap-

tive kept us waiting for 48

minutes and 19 seconds.

Our pocket calculator gave

us a speed of 93 KByte/s

for Captive – that’s around

about DSL speed. It hardly

seems practical to work

with files of this size

in real life scenarios,

although the tool might be

fine for the occasional text

document or image file.

Captive but Cheeky

The GPL licensed con-

tender, Captive, is

available as a binary RPM

or tar.gz archive from the

developer’s project page,

or you can build Captive

from the source code. After

completing the install, you

need to have access to a

few Windows XP files. The

neat captive-install-acquire

tool will help you to find

the right files. It not only

searches the directories

where you suspect the files

might reside, but can even

download a Windows XP

service pack from the

Microsoft download server

if asked to do so.

The fairly sparse docu-

mentation correctly

informs users that they do

need to own a valid XP

license to use Captive. The

remaining procedure is

automated: when you

mount an NTFS partition,

the drivers automagically

compile and mount the

partition in next to no

time. The mount entry is

awesome:

Figure 1: Captive is a free software tool, a complex structure comprised of a kernel

module and a main userspace module. The latter tricks the Windows NTFS driver

into running on Linux.

Read Performance

If you use one of our two

test candidates to mount your NTFS par-

tition, you will not be able to use the

kernel NTFS drivers. Because of this

restriction, we required both drivers

to prove that they would not be affec-

ting our machine’s read performance.

Paragon’s kernel driver achieved speeds

of around 2.1 MByte/s, reading 265

MBytes in two minutes and six seconds.

As a comparison, the original NTFS ker-

nel module copied the same file in just

35.7. The original kernel module is thus

far quicker than the Paragon module.

We had already enjoyed a fairly

/dev/hda4 on /mnt/captive- U

windows2000 type captive-ntfs U

(user=root,fs=captivefs, U

mntent.mnt_fsname= U

/dev/hda4,mntent.mnt_type U

=captive-ntfs,dir_cache_entries U

=0,image=/dev/hda4,noauto, U

captive_options=--disk; U

--rw;--load-module= U

/var/lib/captive/ntoskrnl.exe; U

--filesystem=/var/lib/captive U

/ntfs.sys;--sandbox-server= U

/usr/sbin/captive-sandbox U

-server;--bug-pathname=/var U

/lib/captive/bug-%FT%T. U

captivebug.xml.gz; U

--syslog;--rw,server_socket U

=/tmp/lufsd2057093082, U

server_pid=6209)

If you look closely, you will see that the

list includes the Windows files. From a

functionality point of view, the software

was really convincing: it automagically

detects the right character set – UTF-8 in

our test – and unpacks NTFS-com-

pressed files. Again, the tool can not

decrypted NTFS-encrypted files, but that

REVIEWS

Mounting NTFS

Figure 2: Paragon’s NTFS module converts special characters in file names – in this case German umlauts

– correctly, assuming you specify the character set in the mount command.

amounts of data.

Captive users can also expect heavy

loads. The fact that the driver lives in

userspace rather than kernel space will

make very little difference in a produc-

tion environment. But we very much

doubt that users will be happy with the

abysmal read and write performance that

this NTFS emulator provides.

Captive is acceptable for occasionally

exchanging small files. Moving an MPEG

movie would probably exceed your hard

disk’s life expectancy. In contrast to this,

the commercial NTFS for Linux handles

the required tasks at acceptable speeds.

This said, NTFS for Linux is not suitable

for partitions on hard-working produc-

tion machines, as the disaster that struck

when we tried to run a synthetic bench-

mark (Boniee++) just goes to show.

lengthy coffee break thanks to the Cap-

tive program, but we could have taken a

trip downtown while the read test was

running. After about three hours of

hectic flashing, the hard disk LED finally

stopped. The computer was more or less

unusable the whole time. To make things

worse, the test actually failed: it appears

that a critical Captive component had

collapsed under the load, taking the

kernel driver, the mount point, the cp

process, the shell, and finally the

window manager down with it. X11 was

still running. The computer freed up its

resources after the act, but that was only

a small consolation to us.

performance with large files.

NTFS for Linux 3.0 read from and

wrote to NTFS fairly quickly. The system

load kernel side was quite heavy, but in

some situations you may be able to live

with that if you are handling small

■

Test Procedure

Both solutions are designed to support

dual boot desktops. In this light, we decided

to test both products on a normal desktop

PC rather than on a high-performance

server machine. In our case this was a

Pentium 4 Celeron with a 2GHz CPU, 256MB

RAM and an 80GB ATAPI hard disk. The

machine’s main operating system was Suse

Linux 9.1 Professional with the original Suse

kernel 2.6.3. We formatted the Linux parti-

tion with Ext 3. The NTFS partition came

courtesy of Windows 2000 Professional with

current service packs.

We originally wanted to use Bonnie++ for

the performance tests. Bonnie++ feels per-

fectly at home on Ext 3 partitions. But our

first attempt to run Bonnie++ with Paragon’s

fast software ended in a disaster. We told

Bonnie++ to work with 512 Mbytes and

50x1024 files – just for comparison’s sake,

this takes just a few minutes on the Ext 3

partition. Alas, the Paragon driver, and the

whole system froze for about the next six

hours. The mouse and keyboard showed no

response at all, there was no discernible hard

disk activity, and of course there were no

results.

We quit Bonnie++ by pressing [Ctrl]+[C],

but this was not the end of the story as

Bonnie++ wanted to delete all 50000 files.

To put our lab machine out of its misery, we

decided to kill the process after about a

quarter of an hour, and we manually cleaned

up the wreckage on the Windows 2000

partition. This left us with a 265MByte file

copy as a “benchmark.”We measured the

read performance by writing to device null

and the write performance by copying

between the partitions. The procedure took

up to an hour in some cases.

Conclusion

Both contenders provide stable writing

facilities and support critical NTFS

attributes. We did not experience any

NTFS filesystem corruption during our

lab sessions. And this puts them miles

ahead of the kernel-based NTFS driver.

Both drivers deserve our recommenda-

tion in this respect, but we had to take

Captive’s medal away because of its read

Benefits for Linux Magazine Readers

INFO

Linux Magazine readers who install the

Suse Linux 9.1 Pro distribution from the

DVD with this issue can download the

current NTFS for Linux 3.0 file system driver

from the website at [3] free of charge.

The driver is fully functional and not time

bombed. If you have purchased Suse Linux

9.1 – no matter whether you have the

Personal or Professional version – you

should get along fine with the software

download. The installation script is not

supplied, however, all you need to do is bind

the right object file into your kernel using the

insmod filename command. The mount com-

mand should now work as described in this

article.

Note that for compatibility reasons insmod

may refuse to work with the UFSD driver

after this update. This is hardly surprising as

the kernel module is linked against a specific

kernel version, and this is a feature that you

normally only get with the US$ / EUR 69.95

commercial version of the program. On the

brighter side, Paragon is offering Linux Mag-

azine readers a fairly substantial discount. If

you order via [4], and enter the right coupon

code the license will cost you US$ / EUR

34.97.

[1] Paragon Software Group:

http://www.paragon.ag/

[2] Jan Kleinert; Paragon Mount Everything

3.0 Professional test. Linux Magazine,

Issue 38 / January 2004, p33

[3] NTFS for Linux 3 driver for Suse Linux 9.1

free of charge for readers of Linux

Magazine: http://www.ntfs-linux.com/

linux-magazine.htm

[4] Reader discount on NTFS for Linux 3:

https://secure.element5.com/esales/cart.h

tml?PRODUCT[516868]=1&COUPON1=NTF

SCT&currencies=USD ,

Coupon Code: NTFSCT

December 2004

www.linux-magazine.com

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