RAID处于降级模式时如何重新添加驱动器？

我正在运行一个非托pipe的Ubuntu服务器，并且由于最近的性能问题，并向提供商发送请求只收到以下响应：

“亲爱的客户，

根据要求我们检查了您的驱动器。 两个驱动器通过testing没有任何错误，并没有显示任何临界值。 我们注意到RAID处于降级状态，所以您需要在这里重新添加驱动器到arrays：

-----------------%<----------------- Personalities : [raid1] md3 : active raid1 sda4[0] 1839089920 blocks super 1.2 [2/1] [U_] md2 : active raid1 sda3[0] 1073610560 blocks super 1.2 [2/1] [U_] md1 : active raid1 sda2[0] 523968 blocks super 1.2 [2/1] [U_] md0 : active raid1 sda1[0] 16768896 blocks super 1.2 [2/1] [U_] unused devices: <none> -----------------%<-----------------" 

谷歌表示，U_表示驱动器出现故障，这似乎与支持所说的相矛盾。 我怎么从这里开始？

• RAID 5用于SSD驱动器。
• 5400转与7200转2.5英寸硬盘在RAID – 任何真正的区别？
• 我可以预测每分钟最大写入磁盘/ RAIDarrays吗？
• Adaptec 2420SA RAID 1在1周后重build66％
• 分离EBS卷（在LVM中）需要很长时间

就像是

 mdadm /dev/mdX -r /dev/sdaY mdadm /dev/mdX -a /dev/sdaY 

如果是这样，我的情况是什么X和Y？ 如果需要更多关于我的configuration的信息，请告诉我。

编辑，更多信息如下：

 root@Ubuntu-1204-precise-64-minimal /home # df -h Filesystem Size Used Avail Use% Mounted on /dev/md2 1008G 26G 931G 3% / none 4.0K 0 4.0K 0% /sys/fs/cgroup udev 16G 4.0K 16G 1% /dev tmpfs 3.2G 504K 3.2G 1% /run none 5.0M 0 5.0M 0% /run/lock none 16G 0 16G 0% /run/shm none 100M 0 100M 0% /run/user /dev/md1 488M 66M 397M 15% /boot /dev/md3 1.7T 31G 1.6T 2% /home root@Ubuntu-1204-precise-64-minimal /home # mdadm -D /dev/md0 /dev/md0: Version : 1.2 Creation Time : Wed Nov 6 08:02:41 2013 Raid Level : raid1 Array Size : 16768896 (15.99 GiB 17.17 GB) Used Dev Size : 16768896 (15.99 GiB 17.17 GB) Raid Devices : 2 Total Devices : 1 Persistence : Superblock is persistent Update Time : Wed Dec 21 03:50:13 2016 State : clean, degraded Active Devices : 1 Working Devices : 1 Failed Devices : 0 Spare Devices : 0 Name : rescue:0 UUID : 872ad258:c42ccb36:e9e19c96:98b55ee9 Events : 816844 Number Major Minor RaidDevice State 0 8 1 0 active sync /dev/sda1 1 0 0 1 removed root@Ubuntu-1204-precise-64-minimal /home # mdadm -D /dev/md1 /dev/md1: Version : 1.2 Creation Time : Wed Nov 6 08:02:41 2013 Raid Level : raid1 Array Size : 523968 (511.77 MiB 536.54 MB) Used Dev Size : 523968 (511.77 MiB 536.54 MB) Raid Devices : 2 Total Devices : 1 Persistence : Superblock is persistent Update Time : Wed Dec 21 07:30:55 2016 State : clean, degraded Active Devices : 1 Working Devices : 1 Failed Devices : 0 Spare Devices : 0 Name : rescue:1 UUID : 18cb39fc:9eaea61c:0074a6c2:661b5862 Events : 387 Number Major Minor RaidDevice State 0 8 2 0 active sync /dev/sda2 1 0 0 1 removed root@Ubuntu-1204-precise-64-minimal /home # mdadm -D /dev/md2 /dev/md2: Version : 1.2 Creation Time : Wed Nov 6 08:02:42 2013 Raid Level : raid1 Array Size : 1073610560 (1023.87 GiB 1099.38 GB) Used Dev Size : 1073610560 (1023.87 GiB 1099.38 GB) Raid Devices : 2 Total Devices : 1 Persistence : Superblock is persistent Update Time : Wed Dec 21 07:58:52 2016 State : active, degraded Active Devices : 1 Working Devices : 1 Failed Devices : 0 Spare Devices : 0 Name : rescue:2 UUID : eb9be750:7ff778b4:31fd7ce9:9d86d191 Events : 38799724 Number Major Minor RaidDevice State 0 8 3 0 active sync /dev/sda3 1 0 0 1 removed root@Ubuntu-1204-precise-64-minimal /home # mdadm -D /dev/md3 /dev/md3: Version : 1.2 Creation Time : Wed Nov 6 08:02:42 2013 Raid Level : raid1 Array Size : 1839089920 (1753.89 GiB 1883.23 GB) Used Dev Size : 1839089920 (1753.89 GiB 1883.23 GB) Raid Devices : 2 Total Devices : 1 Persistence : Superblock is persistent Update Time : Wed Dec 21 07:57:41 2016 State : clean, degraded Active Devices : 1 Working Devices : 1 Failed Devices : 0 Spare Devices : 0 Name : rescue:3 UUID : c9b748ef:332d3bf9:5fa8fef1:5b433b0a Events : 7429895 Number Major Minor RaidDevice State 0 8 4 0 active sync /dev/sda4 1 0 0 1 removed 

 mdadm <RAID Device> -a <Device to add into the array> 

 $ mdadm /dev/md0 -a /dev/sdc1 mdadm: re-added /dev/sdc1 

 Number Major Minor RaidDevice State 0 8 17 0 active sync /dev/sdb1 2 8 33 1 spare rebuilding /dev/sdc1 

 $ cat /proc/mdstat Personalities : [linear] [multipath] [raid0] [raid1] [raid6] [raid5] [raid4] [raid10] md0 : active raid1 sdc1[2] sdb1[0] 976759936 blocks [2/1] [U_] [>....................] recovery = 1.2% (12409024/976759936) finish=195.2min speed=82312K/sec unused devices: <none> 

 $ ls /mnt/raid1 Music lost+found Images Films Misc 

 sgdisk -R /dev/sdb /dev/sda sgdisk -G /dev/sdb mdadm /dev/md0 -a /dev/sdb1 mdadm /dev/md1 -a /dev/sdb2 mdadm /dev/md2 -a /dev/sdb3 mdadm /dev/md3 -a /dev/sdb4 

 cat /proc/mdstat 

 Personalities : [linear] [multipath] [raid0] [raid1] [raid6] [raid5] [raid4] [raid10] md3 : active raid1 sdb4[2] sda4[0] 1839089920 blocks super 1.2 [2/2] [UU] md1 : active raid1 sdb2[2] sda2[0] 523968 blocks super 1.2 [2/2] [UU] md2 : active raid1 sdb3[2] sda3[0] 1073610560 blocks super 1.2 [2/2] [UU] md0 : active raid1 sdb1[2] sda1[0] 16768896 blocks super 1.2 [2/2] [UU]