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Mirror - How do I reestablish a mirror with a new drive?

pistonpilot

Mirror - How do I reestablish a mirror with a new drive?
« on: May 03, 2006, 08:54:44 AM »
I had a system with two identical IBM 20gb drives.  hdb died.  I found another 20gb drive, replaced it, and it booted.  It was previously booting on the good drive once I pulled the data cable from the bad one.

on boot it gives the same error - saying it has no spare to use.  

Is this as easy as designating hdb as the spare?  And if so how do I do that?  /dev/hda is the origina drive.




/dev/hda:
 
 Model=IC35L020AVER07-0, FwRev=ER2OA44A, SerialNo=SVNSV0C3424
 Config={ HardSect NotMFM HdSw>15uSec Fixed DTR>10Mbs }
 RawCHS=16383/16/63, TrkSize=0, SectSize=0, ECCbytes=40
 BuffType=DualPortCache, BuffSize=1916kB, MaxMultSect=16, MultSect=16
 CurCHS=16383/16/63, CurSects=16514064, LBA=yes, LBAsects=40188960
 IORDY=on/off, tPIO={min:240,w/IORDY:120}, tDMA={min:120,rec:120}
 PIO modes: pio0 pio1 pio2 pio3 pio4
 DMA modes: mdma0 mdma1 mdma2 udma0 udma1 udma2 udma3 udma4 *udma5
 AdvancedPM=yes: disabled (255) WriteCache=enabled
 Drive Supports : ATA/ATAPI-5 T13 1321D revision 1 : ATA-2 ATA-3 ATA-4 ATA-5
 
[root@server root]# hdparm -i /dev/hdb
 
/dev/hdb:
 
 Model=MDT MD200EB-00CPF0, FwRev=06.04G06, SerialNo=MDT-MCAHE1130031
 Config={ HardSect NotMFM HdSw>15uSec SpinMotCtl Fixed DTR>5Mbs FmtGapReq }
 RawCHS=16383/16/63, TrkSize=57600, SectSize=600, ECCbytes=40
 BuffType=DualPortCache, BuffSize=2048kB, MaxMultSect=16, MultSect=16
 CurCHS=16383/16/63, CurSects=16514064, LBA=yes, LBAsects=39102336
 IORDY=on/off, tPIO={min:120,w/IORDY:120}, tDMA={min:120,rec:120}
 PIO modes: pio0 pio1 pio2 pio3 pio4
 DMA modes: mdma0 mdma1 mdma2 udma0 udma1 udma2 udma3 udma4 *udma5
 AdvancedPM=no WriteCache=enabled
 Drive Supports : Reserved : ATA-1 ATA-2 ATA-3 ATA-4 ATA-5

nick

Mirror - How do I reestablish a mirror with a new drive?
« Reply #1 on: May 03, 2006, 04:59:17 PM »
My favorite mode of doing it is this:

sfdisk -d /dev/hda > hda.out
sfdisk /dev/hdb < hda.out

then raidhotadd the partitions..

Before you do it though, have a look at the sfdisk manpages, and other stuff, don't just copy my example blindly.

pistonpilot

Mirror - How do I reestablish a mirror with a new drive?
« Reply #2 on: May 03, 2006, 10:30:57 PM »
Two questions:

1.  The command worked on the output, but the new 20gb drive must be slightly smaller than the first disk.  

Assuming this, can I shrink the size one of the partitions on hda (swap perhaps) so the partitions can fit on hdb?

And taking into account the sizes I originally posted, by how much?  

2.  Can this be done while it is mounted?  And if not, how do you unmount the swap partition so that it can be shrunk?  Maybe I could put the swap on hdb temporarily while I adjust the size on hda.



[root@server root]# sfdisk -d /dev/hda > hda.out
[root@server root]# less hda.out
[root@server root]# sfdisk /dev/hdb < hda.out
Checking that no-one is using this disk right now ...
OK

Disk /dev/hdb: 2434 cylinders, 255 heads, 63 sectors/track
Old situation:
Units = megabytes of 1048576 bytes, blocks of 1024 bytes, counting from 0

   Device Boot Start   End     MB   #blocks   Id  System
/dev/hdb1         0      -      0         0    0  Empty
/dev/hdb2         0      -      0         0    0  Empty
/dev/hdb3         0      -      0         0    0  Empty
/dev/hdb4         0      -      0         0    0  Empty
Warning: given size (39439575) exceeds max allowable size (38893365)

sfdisk: bad input
[root@server root]#

nick

Mirror - How do I reestablish a mirror with a new drive?
« Reply #3 on: May 04, 2006, 05:05:52 PM »
1. It looks to be about 546210 (blocks?) smaller, if my calculations are correct, that's about 53 meg, but I could be off by a decimal point somewhere (wouldn't surprise me, math was never amy strong suite)..

2. You can "kill" swap by doing a swapoff, as long as the system isn't swapping, it shouldn't be a big deal, then resize the swap partition (fsdisk can do it) , and swapon, changing the size of hdb to match..

3. Please, read a little before doing this, I'm not an expert, all I can offer is what I know :)

Offline warren

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Mirror - How do I reestablish a mirror with a new drive?
« Reply #4 on: May 04, 2006, 10:59:15 PM »
A good run down on recovering from a failed RAID1 :
Shamelessly and with gratitude  :pint: , copied from Darrell May ( this saved my but once  :hammer:  )

Quote

RAID1 Recovery HowTo
 Suitable for: e-smith 4.1.2/Mitel SME5
Author:  Darrell May
Contributor:  
Problem:  You want to easily recover from a RAID1 failure.

Solution:  Implement the steps outlined in the RAID1 Monitor HowTo.  Next follow these steps:
 

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STEP 1:  Backup your computer!
I can not stress this point strongly enough.  Your first priority on a failed RAID1 system should be to perform an immediate backup.

So, DO IT NOW!

[root@myezserver /root]# /sbin/e-smith/backup
 

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STEP 2: Power down, replace the failed drive, power up.
First, before we continue, I just want to show you that for testing purposes only, to completely erase a drive, do the following:

[root@myezserver /root]# dd if=/dev/zero of=/dev/hdb

This will write zeroes across the entire /dev/hdb drive.  Remember for all command-line entries in this HowTO to substitute your correct /dev/hdX where:
/dev/hda = primary master
/dev/hdb = primary slave
/dev/hdc = secondary master
/dev/hdd = secondary slave
 

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Step 3: Recover the partition information and use this information to quickly prepare the replacement drive.
[root@myezserver /root]# cat /root/raidmonitor/sfdisk.out
# partition table of /dev/hda
unit: sectors

/dev/hda1 : start=       63, size=  530082, Id=fd, bootable
/dev/hda2 : start=   530145, size=39487770, Id= 5
/dev/hda3 : start=        0, size=       0, Id= 0
/dev/hda4 : start=        0, size=       0, Id= 0
/dev/hda5 : start=   530208, size=   32067, Id=fd
/dev/hda6 : start=   562338, size=39455577, Id=fd
# partition table of /dev/hdb
unit: sectors

/dev/hdb1 : start=       63, size=  530082, Id=fd, bootable
/dev/hdb2 : start=   530145, size=39487770, Id= 5
/dev/hdb3 : start=        0, size=       0, Id= 0
/dev/hdb4 : start=        0, size=       0, Id= 0
/dev/hdb5 : start=   530208, size=   32067, Id=fd
/dev/hdb6 : start=   562338, size=39455577, Id=fd
Cut and paste your correct # partition table of /dev/hdX.  In my case I am replacing /dev/hdb so this is the information I need to transfer into a file for quick import:

[root@myezserver /root]# pico hdb.out

Which now contains the following entries, right?:

# partition table of /dev/hdb
unit: sectors

/dev/hdb1 : start=       63, size=  530082, Id=fd, bootable
/dev/hdb2 : start=   530145, size=39487770, Id= 5
/dev/hdb3 : start=        0, size=       0, Id= 0
/dev/hdb4 : start=        0, size=       0, Id= 0
/dev/hdb5 : start=   530208, size=   32067, Id=fd
/dev/hdb6 : start=   562338, size=39455577, Id=fd

Next perform the partition table import using the sfdisk command as shown below:

[root@myezserver /root]# sfdisk /dev/hdb < hdb.out
Checking that no-one is using this disk right now ...
OK

Disk /dev/hdb: 2491 cylinders, 255 heads, 63 sectors/track
Old situation:
Empty

New situation:
Units = sectors of 512 bytes, counting from 0

   Device Boot    Start       End  #sectors  Id  System
/dev/hdb1   *        63    530144    530082  fd  Linux raid autodetect
/dev/hdb2        530145  40017914  39487770   5  Extended
/dev/hdb3             0         -         0   0  Empty
/dev/hdb4             0         -         0   0  Empty
/dev/hdb5        530208    562274     32067  fd  Linux raid autodetect
/dev/hdb6        562338  40017914  39455577  fd  Linux raid autodetect
Successfully wrote the new partition table

Re-reading the partition table ...

If you created or changed a DOS partition, /dev/foo7, say, then use dd(1)
to zero the first 512 bytes:  dd if=/dev/zero of=/dev/foo7 bs=512 count=1
(See fdisk(8).)
 

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STEP 4:  Review your last known good RAID configuration:
[root@myezserver /root]# /usr/local/bin/raidmonitor -v

ALARM! RAID configuration problem

Current configuration is:

Personalities : [raid1]
read_ahead 1024 sectors
md2 : active raid1 hda1[0] 264960 blocks [2/1] [U_]
md0 : active raid1 hda5[0] 15936 blocks [2/1] [U_]
md1 : active raid1 hda6[0] 19727680 blocks [2/1] [U_]
unused devices: <none>

Last known good configuration was:

Personalities : [raid1]
read_ahead 1024 sectors
md2 : active raid1 hdb1[1] hda1[0] 264960 blocks [2/2] [UU]
md0 : active raid1 hdb5[1] hda5[0] 15936 blocks [2/2] [UU]
md1 : active raid1 hdb6[1] hda6[0] 19727680 blocks [2/2] [UU]
unused devices: <none>
 

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STEP 5:  Add your newly prepared and correctly partitioned hard drive into the RAID1 array.  You use the information above as your guide:
[root@myezserver /root]# /sbin/raidhotadd /dev/md2 /dev/hdb1
[root@myezserver /root]# /sbin/raidhotadd /dev/md0 /dev/hdb5
[root@myezserver /root]# /sbin/raidhotadd /dev/md1 /dev/hdb6
 

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STEP 6:  Use raidmonitor to watch the recovery process.  Note this information will also be e-mailed to root every 15 min. until the recovery is completed.
[root@myezserver /root]# /usr/local/bin/raidmonitor -v

ALARM! RAID configuration problem

Current configuration is:

Personalities : [raid1]
read_ahead 1024 sectors
md2 : active raid1 hdb1[1] hda1[0] 264960 blocks [2/2] [UU]
md0 : active raid1 hdb5[1] hda5[0] 15936 blocks [2/2] [UU]
md1 : active raid1 hdb6[2] hda6[0] 19727680 blocks [2/1] [U_] recovery=5% finish=10.0min
unused devices: <none>

Last known good configuration was:

Personalities : [raid1]
read_ahead 1024 sectors
md2 : active raid1 hdb1[1] hda1[0] 264960 blocks [2/2] [UU]
md0 : active raid1 hdb5[1] hda5[0] 15936 blocks [2/2] [UU]
md1 : active raid1 hdb6[1] hda6[0] 19727680 blocks [2/2] [UU]
unused devices: <none>
 

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STEP 7:  Recover and restore the last known good master boot record (MBR) onto the drive you just replaced:
[root@myezserver /root]# /sbin/lilo -C /root/raidmonitor/lilo.conf -b /dev/hdb
 

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STEP 8:  Shutdown the server, reboot and test the RAID functions
If you have the time, you should test the RAID functionality to make sure the server will boot under simulated hdd failures.

start by booting with both drives attached
power down, disconnect one of the drives, power up, check boot
power down, reconnect the drive, power up and rebuild the array as above repeating steps 5 and 6 only
power down, disconnect the other drive, power up, check boot
power down, reconnect the drive, power up and rebuild the array as above repeating steps 5 and 6 only
OK, now you can confidently say your ready for anything.  Remember if anything goes wrong here, you simply reconnect all the hardware, perform a fresh RAID install and then restore from your backup tape.  You did perform STEP 1 correct?
 

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STEP 9:  When all looks well, re-initialze raidmonitor:
[root@myezserver /root]# /usr/local/bin/raidmonitor -iv
 

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STEP 10: Go have drink.  Job well done ;->  


Warren