我有一个 MDADM 阵列，其中有四个 1TB 磁盘，采用 RAID5 配置。以下是相关部分mdadm --detail /dev/md1：
Version : 00.90
Raid Level : raid5
Array Size : 2929537920 (2793.83 GiB 2999.85 GB)
Used Dev Size : 976512640 (931.28 GiB 999.95 GB)
Raid Devices : 4
Total Devices : 4
Preferred Minor : 1
Persistence : Superblock is persistent
它显示该阵列为 2.8TB。如下fdisk -l /dev/md1：
Disk /dev/md1: 2999.8 GB, 2999846830080 bytes
2 heads, 4 sectors/track, 732384480 cylinders
Units = cylinders of 8 * 512 = 4096 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 65536 bytes / 196608 bytes
Disk identifier: 0xffffffff
Disk /dev/md1 doesn't contain a valid partition table
fdisk 也显示为 3TB。但是，df -Th不同意：
Filesystem Type Size Used Avail Use% Mounted on
/dev/md1 ext3 1.8T 1.8T 0 100% /
为什么全部显示/dev/md13TB但空间却限制为2TB？
其他详细信息：Ubuntu 10.10
更新：
$ tune2fs -l /dev/md1：
tune2fs 1.41.12 (17-May-2010)
Filesystem volume name: <none>
Last mounted on: <not available>
Filesystem UUID: 1b4e9420-61ee-4ffd-817a-28831f2aeaf2
Filesystem magic number: 0xEF53
Filesystem revision #: 1 (dynamic)
Filesystem features: has_journal ext_attr resize_inode dir_index filetype needs_recovery sparse_super large_file
Filesystem flags: signed_directory_hash
Default mount options: (none)
Filesystem state: clean
Errors behavior: Continue
Filesystem OS type: Linux
Inode count: 122068992
Block count: 488255968
Reserved block count: 24412798
Free blocks: 69746292
Free inodes: 121882953
First block: 0
Block size: 4096
Fragment size: 4096
Reserved GDT blocks: 907
Blocks per group: 32768
Fragments per group: 32768
Inodes per group: 8192
Inode blocks per group: 512
RAID stride: 16
RAID stripe width: 32
Filesystem created: Sun Oct 17 01:14:23 2010
Last mount time: Mon Dec 6 01:24:31 2010
Last write time: Mon Dec 6 00:45:41 2010
Mount count: 12
Maximum mount count: 23
Last checked: Sun Dec 5 20:37:35 2010
Check interval: 15552000 (6 months)
Next check after: Fri Jun 3 21:37:35 2011
Reserved blocks uid: 0 (user root)
Reserved blocks gid: 0 (group root)
First inode: 11
Inode size: 256
Required extra isize: 28
Desired extra isize: 28
Journal inode: 8
First orphan inode: 55550208
Default directory hash: half_md4
Directory Hash Seed: 2a386fcb-b24f-4f40-bf4c-7c03489b086c
Journal backup: inode blocks
答案1
创建文件系统后是否添加了第 4 个驱动器？这可能会导致 FS 小于底层设备。
或者，也许你的 ext3 有 1k 个块，因为这会导致 2TB 的文件系统大小限制（ext3 大小限制）。
请发布“sudo tune2fs -l /dev/md1”的输出，并仔细查看块大小行。