Pro/Forums - View Single Post - Help with 4100 Cracked Raid

Phoenix32 · 10-22-2006, 01:11 PM

My mistake, I was not very clear in my intentions in that last post, let me try again here (I was trying not to write a book).

Let's look back a moment. His problem is a bad drive within a RAID 5 arrary and he wants to recover his data. The replacement hard drives he is trying to use are x number of sectors too small for it to rebuild. The key here is he does not want to lose his data. With me so far?

Now, in typical RAID 5 arrarys, the size is based on the first drive in the array, drive 0. Usualy, no matter the size of the drives after drive 0, only the size of drive 0 will be used on the other drives. As an example, if you have a RAID 5 array with 3 x 60 GB and 1 x 80 GB drives (the 80 not being drive 0), you will end up with a RAID 5 array that is 4 x 60 GB, with only 60 Gb of the 80 being used and the remainder not being used and is unavailable. This is where I got my, "as long as it is not drive 0" point. Meaning, as long as his bad drive is not the drive 0, there may be an option here as I will explain.

The solution I am offering here is not perfect by any means. It is a pain in the arse and a small chance it won't even work, but it should recover his data for him, and get his system back up and running in the end. It is the best I can offer short of what a few others have said about aquiring a drive to match the old drives which could be a difficult and expensive adventure.

Step 1 - As long as the bad drive is NOT drive 0 (explained above), replace it with a larger drive you may have laying around (more than 60 GB in this case). Let the system format the drive.

Step 2 - Attempt to add the new larger drive to the RAID 5 array. If it adds it in, great, let it finish rebuilding the arrary. If not, then this solution is not going to work, but I suspect it will let you add it in.

Step 3 - When the array has finished rebuilding (this may take some time), your data should now be available. Back up the now available data to another location. Several copies if possible for safety of the data.

Step 4 - Pull the larger drive out of the SNAP, it is no longer required.

Step 5 - Place one of the newer smaller 60 GB drives in the drive 0 position (so the smaller size is used for the array). If the 2 new drives (he said he bought 2) are different in size, use the smallest of the 2. Smaller and smallest here are defined as fewest sector count. The reason for this is so that if he has this problem again in the future, he will not have to go through this again (since the size is based on drive 0). Since the other drives in the array are most likely the same age and up/use time as the now failed/bad drive, it is assumed the other drives may not be too far behind for failure.

Step 6 - Optional - replace one of the still good, but older drives in the array with the second new drive. Might as well while you're in there working.

Step 7 - Format all 4 drives in the SNAP (2 new and 2 older, with one of the newer drives in the drive 0 position).

Step 8 - Build a new RAID 5 array with the now freshly formatted drives. This new RAID 5 array should be size based on one of the newer/smaller drives now, and thus if another of the drives fails, a replacement should be a simple swap out replacement.

Step 9 - Put your backed up data back onto the SNAP with the new freshly build RAID 5 array. This should have you back where you wanted to be.

Again, it is a pain in the arse, but it should work. The data should now be saved, the SNAP back up and running, and as a bonus, easier to repair should another drive fail. It's not perfect, it has a small chance it wont work, but it is the best I can offer if an exact replacement drive cannot be aquired. Just another idea for the pool of ideas.

I hope I cleared up what I was trying to say now.

10-22-2006, 01:11 PM	#8
Phoenix32 Thermophile Join Date: May 2006 Location: Yakima, WA Posts: 1,282	Re: Help with 4100 Cracked Raid - Trying to replace 1 Drive My mistake, I was not very clear in my intentions in that last post, let me try again here (I was trying not to write a book). Let's look back a moment. His problem is a bad drive within a RAID 5 arrary and he wants to recover his data. The replacement hard drives he is trying to use are x number of sectors too small for it to rebuild. The key here is he does not want to lose his data. With me so far? Now, in typical RAID 5 arrarys, the size is based on the first drive in the array, drive 0. Usualy, no matter the size of the drives after drive 0, only the size of drive 0 will be used on the other drives. As an example, if you have a RAID 5 array with 3 x 60 GB and 1 x 80 GB drives (the 80 not being drive 0), you will end up with a RAID 5 array that is 4 x 60 GB, with only 60 Gb of the 80 being used and the remainder not being used and is unavailable. This is where I got my, "as long as it is not drive 0" point. Meaning, as long as his bad drive is not the drive 0, there may be an option here as I will explain. The solution I am offering here is not perfect by any means. It is a pain in the arse and a small chance it won't even work, but it should recover his data for him, and get his system back up and running in the end. It is the best I can offer short of what a few others have said about aquiring a drive to match the old drives which could be a difficult and expensive adventure. Step 1 - As long as the bad drive is NOT drive 0 (explained above), replace it with a larger drive you may have laying around (more than 60 GB in this case). Let the system format the drive. Step 2 - Attempt to add the new larger drive to the RAID 5 array. If it adds it in, great, let it finish rebuilding the arrary. If not, then this solution is not going to work, but I suspect it will let you add it in. Step 3 - When the array has finished rebuilding (this may take some time), your data should now be available. Back up the now available data to another location. Several copies if possible for safety of the data. Step 4 - Pull the larger drive out of the SNAP, it is no longer required. Step 5 - Place one of the newer smaller 60 GB drives in the drive 0 position (so the smaller size is used for the array). If the 2 new drives (he said he bought 2) are different in size, use the smallest of the 2. Smaller and smallest here are defined as fewest sector count. The reason for this is so that if he has this problem again in the future, he will not have to go through this again (since the size is based on drive 0). Since the other drives in the array are most likely the same age and up/use time as the now failed/bad drive, it is assumed the other drives may not be too far behind for failure. Step 6 - Optional - replace one of the still good, but older drives in the array with the second new drive. Might as well while you're in there working. Step 7 - Format all 4 drives in the SNAP (2 new and 2 older, with one of the newer drives in the drive 0 position). Step 8 - Build a new RAID 5 array with the now freshly formatted drives. This new RAID 5 array should be size based on one of the newer/smaller drives now, and thus if another of the drives fails, a replacement should be a simple swap out replacement. Step 9 - Put your backed up data back onto the SNAP with the new freshly build RAID 5 array. This should have you back where you wanted to be. Again, it is a pain in the arse, but it should work. The data should now be saved, the SNAP back up and running, and as a bonus, easier to repair should another drive fail. It's not perfect, it has a small chance it wont work, but it is the best I can offer if an exact replacement drive cannot be aquired. Just another idea for the pool of ideas. I hope I cleared up what I was trying to say now.