我正在尝试使用mdadm创建一个软件raid5数组：
$linux # mdadm --create --verbose /dev/md0 --level=5 --raid-devices=4 --spare-devices=0 /dev/sda1 /dev/sdb1 /dev/sdc1 /dev/sdd1 mdadm: layout defaults to left-symmetric mdadm: chunk size defaults to 64K mdadm: array /dev/md0 started.
但是在检查/ proc / mdstat时
Personalities : [raid6] [raid5] [raid4]
md0 : active raid5 sdd1[4] sdc1[2] sdb1[1] sda1[0]
2930279808 blocks level 5,64k chunk,algorithm 2 [4/3] [UUU_]
[>....................] recovery = 0.3% (2970496/976759936) finish=186.1min speed=87172K/sec
unused devices: <none>
似乎一个驱动器不活动,所以我检查数组的详细信息：
/dev/md0:
Version : 00.90.03
Creation Time : Tue Jul 21 16:29:53 2009
Raid Level : raid5
Array Size : 2930279808 (2794.53 GiB 3000.61 GB)
Used Dev Size : 976759936 (931.51 GiB 1000.20 GB)
Raid Devices : 4
Total Devices : 4
Preferred Minor : 0
Persistence : Superblock is persistent
Update Time : Tue Jul 21 16:29:53 2009
State : clean,degraded,recovering
Active Devices : 3
Working Devices : 4
Failed Devices : 0
Spare Devices : 1
Layout : left-symmetric
Chunk Size : 64K
Rebuild Status : 0% complete
UUID : ce8b2f40:821d003c:0027688e:a70977ec
Events : 0.1
Number Major Minor RaidDevice State
0 8 1 0 active sync /dev/sda1
1 8 17 1 active sync /dev/sdb1
2 8 33 2 active sync /dev/sdc1
4 8 49 3 spare rebuilding /dev/sdd1
而且似乎只有3个有源设备,只有一个备用设备.
这只是我,还是错在这里？
解决方法
This tutorial涵盖了使用mdadm构建raid5数组.您不能在少于三台设备的情况下使用raid5.
你是什么意思？ Raid5旨在提供冗余以应对一台设备的故障.如果不这样做那么它就不再是raid5了.
问题编辑后编辑：
When creating a RAID5 array,mdadm will automatically create a degraded array with an extra spare drive. This is because building the spare into a degraded array is in general faster than resyncing the parity on a non-degraded,but not clean,array. This feature can be overridden with the --force option.
这似乎就是这样,mdadm将新阵列设置为使用备用降级,然后将备用数据放入以构建阵列.
