Ext3文件系統和reiserfs文件系統現在linux系統上是非常流行的兩種。下面我們來比較一下這兩種文件系統本身對硬盤空間的占用情況。因為我的硬盤分區已經基本定好，不容易更改了，所以就使用文件的方式創建文件來進行比較──畢竟我們這裡比較的不是速度，而是空間──然而這樣做不知是否和實際設備上有區別。
（一）首先，我們需要一個有足夠空閒空間的分區來做這個實驗。我的空閒的空間還不到5GB，所以只好把實驗的每個最大分區做到2GB.我的實驗中先是做100MB的“分區”的比較，然後是1GB分區的比較，最後是2GB分區的比較。我們所需要的工具也十分簡單：dd工具，用於較快地取得一個大文件；創建文件的工具mkfs.ext3和mkfs.reiserfs；df工具，用來查看分區占用情況。
這裡提前說明我的系統的簡單情況：內核為2.6.23.1，自己編譯的。命令替換有alias ll='ls -l'.reiserfs版本是3.6的。
（二）現在就開工：
1.創建100M的文件：
dd if=/dev/zero of=d-ext3fs bs=1M count=100
dd if=/dev/zero of=d-reiserfs bs=1M count=100
2.創建文件系統：
2.1創建ext3文件系統：
togry@xiaowp:~/disks$ sudo mkfs.ext3 d-ext3fs
mke2fs 1.40.4 (31-Dec-2007)
d-ext3fs is not a block special device.
Proceed anyway? (y,n) y
Filesystem label=
OS type: Linux
Block size=1024 (log=0)
Fragment size=1024 (log=0)
25688 inodes, 102400 blocks
5120 blocks (5.00%) reserved for the super user
First data block=1
Maximum filesystem blocks=67371008
13 block groups
8192 blocks per group, 8192 fragments per group
1976 inodes per group
Superblock backups stored on blocks:
8193, 24577, 40961, 57345, 73729
Writing inode tables: done
Creating journal (4096 blocks): done
Writing superblocks and filesystem accounting information: done
This filesystem will be automatically checked every 31 mounts or
180 days, whichever comes first. Use tune2fs -c or -i to override.
2.2創建reiserfs文件系統：
togry@xiaowp:~/disks$ sudo mkfs.reiserfs d-reiserfs
mkfs.reiserfs 3.6.19 (2003 www.namesys.com)
A pair of credits:
Lycos Europe (www.lycos-europe.com) had a support contract with us that
consistently came in just when we would otherwise have missed payroll, and that
they kept doubling every year. Much thanks to them.
Jeremy Fitzhardinge wrote the teahash.c code for V3. Colin Plumb also
contributed to that.
d-reiserfs is not a block special device
Use -f to force over
///////////////呵呵，不讓我默認在文件上創建文件系統。
togry@xiaowp:~/disks$ sudo mkfs.reiserfs d-reiserfs -f
mkfs.reiserfs 3.6.19 (2003 www.namesys.com)
A pair of credits:
The Defense Advanced Research Projects Agency (DARPA, www.darpa.mil) is
the
primary sponsor of Reiser4. DARPA does not endorse this project; it mer
ely
sponsors it.
Jeremy Fitzhardinge wrote the teahash.c code for V3. Colin Plumb a
lso
contributed to that.
d-reiserfs is not a block special device
Continue (y/n):y
Guessing about desired format.. Kernel 2.6.23.1.build51 is running.
Format 3.6 with standard journal
Count of blocks on the device: 25600
Number of blocks consumed by mkreiserfs formatting process: 8212
Blocksize: 4096
Hash function used to sort names: "r5"
Journal Size 8193 blocks (first block 18)
Journal Max transaction length 1024
inode generation number: 0
UUID: 3bb7a2da-b78a-462f-9ea0-a004171c8667
Initializing journal - 0%....20%....40%....60%....80%....100%
Syncing..ok
Tell your friends to use a kernel based on 2.4.18 or later, and especially n
ot a
kernel based on 2.4.9, when you use reiserFS. Have fun.
ReiserFS is successfully created on d-reiserfs.
3.這樣創建好文件系統之後，開始掛載它們，查看他們的可用空間吧。
togry@xiaowp：~/disks$ sudo mount d-ext3fs ext/ -t ext3 -o loop
togry@xiaowp：~/disks$ sudo mount d-reiserfs rei/ -t reiserfs -o loop
togry@xiaowp：~/disks$ df
文件系統 1K-塊 已用 可用 已用% 掛載點
……（此處將不相干的東西略去）
/home/togry/disks/d-ext3fs
99150 5664 88366 7% /home/togry/disks/ext
/home/togry/disks/d-reiserfs
102392 32840 69552 33% /home/togry/disks/rei
喲！reiserfs文件系統竟然占用了這麼大的地方，三分之一都沒有了。
4.創建兩個1GB的文件進行比較。相比前面，這裡要簡略一些。
drwxr-xr-x 2 togry togry 48 2008-01-11 17：07 ext
-rw-r——r—— 1 togry togry 1073741824 2008-01-22 20：53 ext3
drwxr-xr-x 2 togry togry 48 2008-01-11 17：07 rei
-rw-r——r—— 1 togry togry 1073741824 2008-01-22 20：50 reiserfs
其中etc3和reiserfs兩個文件就是“設備”。
5.創建文件系統
togry@xiaowp:~/disks$ sudo mkfs.reiserfs reiserfs -f
mkfs.reiserfs 3.6.19 (2003 www.namesys.com)
A pair of credits:
Edward Shushkin wrote the encryption and compression file plugins, and the V3
journal relocation code.
Lycos Europe (www.lycos-europe.com) had a support contract with us that
consistently came in just when we would otherwise have missed payroll, and that
they kept doubling every year. Much thanks to them.
reiserfs is not a block special device
Continue (y/n):y
Guessing about desired format.. Kernel 2.6.23.1.build51 is running.
Format 3.6 with standard journal
Count of blocks on the device: 262144
Number of blocks consumed by mkreiserfs formatting process: 8219
Blocksize: 4096
Hash function used to sort names: "r5"
Journal Size 8193 blocks (first block 18)
Journal Max transaction length 1024
inode generation number: 0
UUID: 2b05d990-54b3-49c7-a197-79807a173c5b
Initializing journal - 0%....20%....40%....60%....80%....100%
Syncing..ok
Tell your friends to use a kernel based on 2.4.18 or later, and especially not a
kernel based on 2.4.9, when you use reiserFS. Have fun.
ReiserFS is successfully created on reiserfs.
togry@xiaowp:~/disks$ sudo mkfs.ext
mkfs.ext2 mkfs.ext3
togry@xiaowp:~/disks$ sudo mkfs.ext3 ext
ext/ ext3
togry@xiaowp:~/disks$ sudo mkfs.ext3 ext3
mke2fs 1.40.4 (31-Dec-2007)
ext3 is not a block special device.
Proceed anyway? (y,n) y
Filesystem label=
OS type: Linux
Block size=4096 (log=2)
Fragment size=4096 (log=2)
131072 inodes, 262144 blocks
13107 blocks (5.00%) reserved for the super user
First data block=0
Maximum filesystem blocks=268435456
8 block groups
32768 blocks per group, 32768 fragments per group
16384 inodes per group
Superblock backups stored on blocks:
32768, 98304, 163840, 229376
Writing inode tables: done
Creating journal (8192 blocks): done
Writing superblocks and filesystem accounting information: done
This filesystem will be automatically checked every 28 mounts or
180 days, whichever comes first. Use tune2fs -c or -i to override.
6.掛載文件系統之後查看空間的剩余情況
togry@xiaowp：~/disks$ df
文件系統 1K-塊 已用 可用 已用% 掛載點
……
/home/togry/disks/ext3
1032088 34092 945568 4% /home/togry/disks/ext
/home/togry/disks/reiserfs
1048540 32840 1015700 4% /home/togry/disks/rei
togry@xiaowp：~/disks$ df -h
文件系統 容量 已用 可用 已用% 掛載點
……
/home/togry/disks/ext3
1008M 34M 924M 4% /home/togry/disks/ext
/home/togry/disks/reiserfs
1.0G 33M 992M 4% /home/togry/disks/rei
似乎文件空間的占用情況相當了。讓我們再看看2GB文件系統裡的情況：
7.創建文件：
dd if=/dev/zero of=ext3 bs=1G count=2
dd if=/dev/zero of=reiserfs bs=1G count=2
看一下結果：
drwxr-xr-x 2 togry togry 48 2008-01-11 17：07 ext
-rw-r——r—— 1 togry togry 2147483648 2008-01-22 21：30 ext3
drwxr-xr-x 2 togry togry 48 2008-01-11 17：07 rei
-rw-r——r—— 1 togry togry 2147483648 2008-01-22 21：35 reiserfs
8.創建文件系統：
togry@xiaowp:~/disks$ sudo mkfs.ext3 ext3
mke2fs 1.40.4 (31-Dec-2007)
ext3 is not a block special device.
Proceed anyway? (y,n) y
Filesystem label=
OS type: Linux
Block size=4096 (log=2)
Fragment size=4096 (log=2)
262144 inodes, 524288 blocks
26214 blocks (5.00%) reserved for the super user
First data block=0
Maximum filesystem blocks=536870912
16 block groups
32768 blocks per group, 32768 fragments per group
16384 inodes per group
Superblock backups stored on blocks:
32768, 98304, 163840, 229376, 294912
Writing inode tables: done
Creating journal (16384 blocks): done
Writing superblocks and filesystem accounting information: done
This filesystem will be automatically checked every 25 mounts or
180 days, whichever comes first. Use tune2fs -c or -i to override.
togry@xiaowp:~/disks$ sudo mkfs.reiserfs reiserfs -f
mkfs.reiserfs 3.6.19 (2003 www.namesys.com)
A pair of credits:
BigStorage (www.bigstorage.com) contributes to our general fund every month,
and has done so for quite a long time.
Lycos Europe (www.lycos-europe.com) had a support contract with us that
consistently came in just when we would otherwise have missed payroll, and that
they kept doubling every year. Much thanks to them.
reiserfs is not a block special device
Continue (y/n):y
Guessing about desired format.. Kernel 2.6.23.1.build51 is running.
Format 3.6 with standard journal
Count of blocks on the device: 524288
Number of blocks consumed by mkreiserfs formatting process: 8227
Blocksize: 4096
Hash function used to sort names: "r5"
Journal Size 8193 blocks (first block 18)
Journal Max transaction length 1024
inode generation number: 0
UUID: 0d3e668d-77e5-4b5d-a157-a3e937cbc7f4
Initializing journal - 0%....20%....40%....60%....80%....100%
Syncing..ok
Tell your friends to use a kernel based on 2.4.18 or later, and especially not a
kernel based on 2.4.9, when you use reiserFS. Have fun.
ReiserFS is successfully created on reiserfs.
這回創建文件系統的時間都比以前長了。
9.掛載文件系統，看結果：
togry@xiaowp：~/disks$ sudo mount ext3 ext -t ext3 -o loop && sudo mount reiserfs rei -t reiserfs -o loop
togry@xiaowp：~/disks$ df
文件系統 1K-塊 已用 可用 已用% 掛載點
……
/home/togry/disks/ext3
2064208 68680 1890672 4% /home/togry/disks/ext
/home/togry/disks/reiserfs
2097084 32840 2064244 2% /home/togry/disks/rei
togry@xiaowp：~/disks$ d
f -h