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Hello.
I have here a situation. I have found some errors on the surface of a IDE hard-drive. I was thinking doing a disk clone byte-by-byte. Will this clone, somehow put bad sectors on the new hard-drive, or clone the same disk errors??
Will clone work on RAID5 with 4 drives? If i have a failure, will it be able to put back and running on a raid5 ?
Thanks.
Best Regards.
No, the correct method is to replace the defective drive and let the RAID management system rebuild the array.Quote:
Will clone work on RAID5 with 4 drives? If i have a failure, will it be able to put back and running on a raid5 ?
That would depend on the software you use. I would imagine that many drive cloning applications would just fail when they detected that the original was corrupt/damaged. You are supposed to use them before the problem ;)Quote:
I was thinking doing a disk clone byte-by-byte. Will this clone, somehow put bad sectors on the new hard-drive, or clone the same disk errors??
Forensics software (as in criminal investigations) should produce an absolutely identical copy. I know that this is questionable in reality, but for the purposes of your question the answer would be "yes", you will get the defects as well.
The third sort are the data recovery applications. They will attempt to recover as much data as possible from damaged and corrupted disks, but they don't "clone" in the true sense.
I know that if you disk fails in RAID5 i just need to replace, and let the controler do all the work.
What i was saying, if by any change, the 4 disk fail, of course i can't rebuild, if i have a full disk image, if i put the new 4 disk RAID5, will it work ?
But if the error on the drive is hardware, it should be ok to do a Clone Disk.
yuris,
If you lose all your drives you need a new computer.Quote:
What i was saying, if by any change, the 4 disk fail, of course i can't rebuild, if i have a full disk image, if i put the new 4 disk RAID5, will it work ?
Just reinstall from your backups.
As for whether a clone of the entire array would work...............in theory it should, but who is going to clone their entire RAID array twice a day or whatever your backup cycle happens to be?
You would then face the potential issue of the new controller not recognising it?
There is software to perform RAID specific backups.............I would suggest that you look at that. Also consider RAID6 if you want extra redundancy.
You would need to do it before there was an error and for the whole array, not just one disk. Even then, I don't know how reliable it would be. Please remember that although RAID consists of multiple drives, the system considers them to be a whole, single array.Quote:
But if the error on the drive is hardware, it should be ok to do a Clone Disk.
What advantage do you think you might have in cloning an array as opposed to backing it up in the traditional manner? You have got me very intrigued now :D
I'm sorry i wasn't clear.
This are 2 different scenario.
1º My raid5 has backups, it runs in a cycle of 4 hours, no problem there. What i was asking, is, in case of failure of the 4 or 3 drives, i would had to reinstall everthing, configure and the put the recent backups.
My question is, if i have a disk image of my raid5, would it work, putting the S.O, all the configuration including the Database, and configuration files.
If it works, i only would have to put the recent backups, and wouldn't have to worry about installing and configuring everything again.
2º The disk on the drive (1 drive) is in a workstation, and it doesn't have raid, it's just a workstation.
But i was asking if a disk clone would clone erros on the surface of the drive.
If this are hardware flaws, would it corrupt the information when im cloning.
OK, I think I understand. :)
#2. With a single drive your cloning, ghosting or mirroring software will only copy readable files. If it finds damaged or corrupted ones it will either copy them as is, or throw an error. It will not copy stuff in sectors that are marked as bad.
#1. I don't think that it will work due to the nature of RAID arrays. They look on all drives as one, so cloning only works when you are moving from one platform to another or deploying multiple installations. That is, the array is not changing, as it is not being used.
As soon as you start to use a RAID array, you change the contents of the individual drives, so a clone does not work.
Sure, you could use it to restore back to the original installation on a clean set of drives, but why would you want to do that when you have already invested in RAID?
What you are seeming to suggest is already handled by RAID 1............... straight mirroring or "cloning" of the drives.
Otherwise you need one of the more exotic RAID deployments that handles mirroring of some data/drives and striping of others. I have already suggested that you look at RAID6, as that gives you one extra recovery channel.
Otherwise I would suggest a parallel processing environment with duplicate hardware sets in different locations. The issue is obviously that whatever RAID you use, all your drives are in the one location?
As for cloning or mirroring or copying, the rules are the same as for #2 above. It will only copy readable stuff.
That's a solution I employ. Clone a offline image onto a spare drive as a master backup. If I think the raid1 array has a bad image, I rebuild using the spare. Rather backup an entire drive in less than 7 minutes compared to some 1hour+ backup software solution. If I need to do surgery on some particular set of data, I can mount the spare as a regular harddrive and proceed with the modifications.Quote:
Originally Posted by nihil
I also would like to have raid1 on the workstations, but there are limit budgets.
To me the ideal would be, every workstations had raid1 and all the hardware are would be the same, but unfortunately it's not like that, and in this global crises i must try to save money. So my solution would pass using a software to clone the drives.
For your workstations the solution should be quite simple. You just create images/mirrors/ghosts of your standard installations. If anything goes wrong that image can be installed in a matter of minutes
For a server with a RAID5 array, you can afford to lose one drive; with RAID6 this is two drives. Both systems "stripe" data across all the drives in the array, so once it has been in use you cannot selectively replace individual drives as you have no idea where the data physically are.
If you lose more than the allowed number of drives you will have to rebuild the entire array from scratch.
An alternative would be to use a RAID1+5 or similar setup. Here you mirror the operating system, applications, and static data and use striping for the transaction data. This allows for business continuity, although the data would have to be subsequently input to the system once it was restored.
If you lose a pair of mirrored drives then once again you have to rebuild from scratch. The operating system and applications should be easily applied from your latest mirror/ghost image, and the standing data (price lists, customer files, metadata etc.) from your backups.
My main concern regarding cloning an active RAID array is that it sets a restore point. You will have processed data since that point so would need an incremental backup or journalling system to bring your system back up to date.
A lot of cruder backup mechanisms will backup all the data, so you cannot apply it to a cloned system without getting a mass of duplicates etc.