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The term mirroring is often used synonymously with duplexing when, in fact, the two are different:
l Mirroring means that NetWare maintains the same data on two or more partitions connected to the same disk channel.
l Duplexing means that NetWare maintains the same data on two or more partitions connected to different disk channels.
Mirroring protects data against failure of the drive itself, but not against failures in other disk channel components such as host bus adapters (HBAs), disk controllers, cables, and power supplies. Duplexing (or channel mirroring, as it is sometimes called) protects data against failure in any component along the disk channel. Therefore, duplexing provides a higher level of data protection.
The process for mirroring and duplexing partitions is the same from within NetWare's INSTALL utility. When INSTALL goes through the process of recognizing partitions, it also determines which devices are connected to which disk channel. Duplexing happens automatically whenever you mirror two or more partitions that are connected to different controllers or HBAs.
When a NetWare v4.x , v3.x server boots, the OS will automatically synchronize two mirrored partitions if it discovers that one is out of sync (provided it can recognize both devices). This could occur after one or more drives have been replaced or added to the system and are listed in the mirror table. As part of the boot-up process, the OS examines several tables, including the mirror tables. If the device sync bits do not match, re-synchronization will begin 10 seconds after the console colon prompt is displayed.
Here you'll find two procedures that will remirror your partitions in 80% of all cases, however whenever a message appears that your not familiar with, please check the explanatory section.
In case of drive failure :
1. Detect and replace faulty hard drive (with DOS Format and DOS partition if applicable)
2. Copy data from c:\ from the previous drive to the new drive if applicable
3. Boot Hardware
4 Type "Server -NA" (Volumes will not mount because it will not see any NetWare info.)
5. Enter file server name and internal IPX number.
6, Load install (Install must be on c: or on diskette)
7. Enter on Available Disk Options
8. Enter on Mirror\Unmirror disk partitions
9. Disk partition will show Not Mirrored press <F3> to bring into sync.
10. Answer YES to salvage data.
11. In Install Enter on Available Disk Options
12. Enter on Modify disk Partitions and Hot Fix
13. Enter on Device where NetWare Portion is to be created
14. Create the NetWare partition the same size as the original partition
15. In Install enter on Disk options
16. Enter on Mirror/Unmirror disk partitions and mirror drives by selecting the device that holds the
data (check ID) and press Ins, by doing this will make this partition to be the 'master', select other device to be synced in.
In case one volume is in 'Out of Sync' and the other in 'Not Mirrored' status:
1. Make sure both drives are in good working order (replace faulty hard drive if any)
2. Boot Hardware
3 Type "Server -NA" (Volumes will not mount because it will not see any NetWare info.)
4. Enter file server name and internal IPX number.
5, Load install (Install must be on c: or on diskette)
6. Enter on Available Disk Options
8. Enter on Mirror\Unmirror disk partitions
9. Press <F3> on the partition that will show ?Out of Sync', write down ID.
11. Answer YES to Rename Volume Segment (i.e. SYS1)
12. Answer YES to Salvage Data.
13. Enter on Mirror/Unmirror disk partitions
14. Select former ?Out of Sync' device (check ID) and press Ins, by doing this will make this partition to be the ?master', select other device to be synced in.
15. Now it shows both devices ?In Sync', if you press ESC you'll see it is currently mirroring the drives.
16. When finished go to Volume Options, select Volume, rename Volume + Enter
17. Press ESC twice, say Yes to Save Volume Changes
16. Select Mount all Volumes.
Explanatory Section:
Upon drive failure you want to take out the faulty drive (and controller) and bring the system up again, so that users can continue working while you get the replacement drive.
What was once the second device is now the only device in the system. The problem is that this device is still Out Of Sync because you haven't modified it to indicate that it's now alone. Without realizing this, you type the MOUNT SYS command at the console. Immediately, the console displays the following message:
:mount sys
There are no accessible disk drives with NetWare partitions Check to see that the needed disk drivers have been loaded and that your disk drives are properly connected and powered on.
For most people, the first reaction to this message is to think, "Wait a minute--all I did was unmirror the devices. There's still one good disk in there with a NetWare partition on it." The next impulse might be to go into INSTALL and check under "Volume Options" to see if volume SYS is still there. When you do, you see the message
'There are no accessible drives with NetWare partitions. <Press ESCAPE To Continue> '
When you press <Esc>, you see the "Volumes" window--but no volumes are listed.
Now go back to INSTALL's "Mirroring" option and check for a device listed as "Out Of Sync" in the "Partition Mirroring Status" window. In most cases, that's the source of your problem .
The message about there being no accessible disk drives is only a warning message--but, unfortunately, it doesn't indicate what's really happening. Remember that when a drive's status is "Out Of Sync," the OS can no longer recognize volume information on that disk. What the OS is trying to say is that it checked for a device that might have a copy of volume SYS on it to mount, but couldn't find one.
Once you've found the device that is out of sync, you need to modify it so that it knows it's not in a mirrored pair anymore. The help text at the bottom of the INSTALL screen says to press <F3> to restore an "Out Of Sync" partition. So, with the "Out Of Sync" device highlighted, press <F3>. Again, you'll see the message saying that "There are no accessible disk drives with NetWare partitions." As indicated in the message, press <Esc> to continue.
The next box that pops up in the middle of the screen will look something like this:
' Salvage Volume SYS Segment 0? Yes/No '
This is where you need to pay particular attention to how you answer the prompt. There is nothing documented, nor is there any on-line help or warning message that comes up via the OS or the INSTALL utility, that tells you that you might be about to do something destructive. The software simply waits for your decision and then proceeds to do what you have told it to do.
If you want the device to remain volume SYS and retain its data, answer "Yes" to this prompt.
The OS will then modify the drive's tables to indicate that this is a standalone drive, it is no longer part of a mirrored pair, and it contains volume SYS data. The device will then be listed in the "Partition Mirroring Status" window as a "Not Mirrored" device.
If you answer "No" to this prompt, the OS will then proceed to delete the entire volume definition table, and you'll be left with a "raw" NetWare partition containing no volume and no data.
The Volume SYS has been made accessible to the OS again.
After a while you received a replacement for your broken harddisk and you'll down your server and reinstall the harddisk (and controller).
Now, without realizing it, you've introduced two separate devices that both contain the same volume name but have different table information.
If you go into INSTALL and select Mirroring, you'll see two Not Mirrored devices. Everything seems fine there, so you go to the system console, and type the MOUNT SYS command to get the server back up in a hurry. The console now displays a series of warning messages:
:mount sys
WARNING: Volume SYS has multiple definitions for segment 0
WARNING: Volume SYS segment 0 ends at block 625247
and segment 0 starts at block 0
WARNING: Definition for sync 0 of volume SYS removed
WARNING: Definition for volume SYS is invalid
Volume SYS could NOT be mounted
some or all volume segments can not be located
:
The numbers in the second message could be different depending on the size of your volume. The third message is a warning message; even though it says the definition has been removed, it hasn't yet.
All these messages are basically saying is that there are two devices that have the same volume name, and the OS can't determine which one contains the valid volume segment.
Go back into INSTALL and check the volume options, because SYS was there before you downed the server a few minutes ago. At that point, these same messages will start displaying one by one in the middle of the screen. This time, you have to press <Esc> after each one.
Volume SYS has multiple definitions for segment 0. <Press ESCAPE To Continue>
Volume SYS segment 0 ends at block 6247, and segment 0 starts at block 0. <Press ESCAPE To Continue
Definition for sync 0 of volume SYS removed. <Press ESCAPE To Continue>
Definition for volume SYS is invalid. <Press ESCAPE To Continue>
After you've gone through this string of error messages, a box will appear that says:
WARNING: There are currently some invalid volume segment entries in the
volume definition tables. Any new updates made to the volume definition
tables will cause these invalid volume segments to be deleted.
<Press ESCAPE To Continue>
When you press <Esc>, the following prompt appears:
Delete The Invalid Volume Segments? Yes/No
Answer No to this prompt.
Everything up to this point is nothing more than a series of warning messages. When you answer "No," nothing is deleted. You can then determine which device has the most current data on it. If necessary, switch to the colon prompt, unload both disk drivers, and load them one at a time to try to decipher which of the devices contains the most recent volume SYS data. Then unload the driver for the device that you know is more current, load the other driver, delete the volume, and reload the driver. You can then start the remirror process as described above.
Some might be tempted to answer "Yes" to this prompt. If you answer "Yes," the OS does indeed delete the invalid volume segments. But since it couldn't determine which of the devices had the correct (valid) volume segment, it deletes all of the volume definition tables on every device associated with the error. You'll then have to start all over from scratch and redo the volume the way you thought it should have been.
In case you have two devices, one listed as Not Mirrored and the other listed as Out Of Sync.
At this point, you have not unloaded any device drivers--both drivers and associated hardware are present.
Suppose you are familiar with the fact that to get an out of sync device back in sync with itself, you can highlight it in the Partition Mirroring Status window and press <F3> (as explained earlier). When there are multiple devices and you indicate that you want to modify the tables, NetWare is smart enough to not allow you to modify the tables on devices that contain the same volume. So when you press <F3> on the out of sync device, a message similar to the following is displayed:
Warning!! The selected partition contains "volume
SYS segment 0" and that volume is already defined.
<Press ESCAPE To Continue>
When you press <Esc>, a prompt appears that says:
Rename The Volume Segment? Yes/No
Most people will answer "No" because they want the volume's name to remain the same. Another prompt will then appear:
Salvage Volume SYS Segment 0? Yes/No
At this point, most people would answer "Yes" because they do want to salvage the volume.
However, this is a serious mistake--and again, there's no warning prompt or help message to prevent you from doing it. What that does is modify the tables so that one of the devices contains information that is different from the information on the other device. Unfortunately, both devices are still named volume SYS. You're only recourse to recover from this predicament is to do a complete restore of volume SYS from the most recent backup.
If you want to keep the data intact, the safest approach is to answer "Yes" to both prompts.
When you answer "Yes" to the first prompt, you will be asked to enter a new volume name. After you type the name and answer "Yes" to the next prompt about salvaging volume SYS segment 0, you will have two separate devices with the same data, but with different volume names. You can then determine which volume is the most current, delete the other volume, and remirror the devices.
Alternatively, you can answer "No" to both prompts. Before doing so, however, make sure that one of the devices is still in sync and contains the data you want.
When you answer "No" to the prompt about renaming the volume, and also answer "No" to the prompt about salvaging volume SYS segment 0, INSTALL will update the "Partition Mirroring Status" window so that the device is displayed as "Not Mirrored." The OS has deleted the volume definition table because you said, in essence, that you don't want to rename the volume and you don't want to keep the data. So it simply makes this another available partition with no volume and no data. You can then remirror the partitions.
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