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Topic: Onboard RAID1 questions (Read 7145 times) previous topic - next topic
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Onboard RAID1 questions

I am considering the use of raid1 as a "backup" solution.
As I have never used such a system, I have a few questions related to onboard raid controllers.

I understand that those controllers are mainly software raid, so they are using the processor power. But is it possible to boot on such a raid1 array, or can this only be used as a non-system partition ?

Is it possible to remove one of the drives (for electrical safety reasons) and to only plug it weekly to synchronize data ?

Onboard RAID1 questions

Reply #1 –
According to the manual, my Intel board can boot from the onboard SATA RAID controller, but I have not tried it. My guess is that most onboard RAID controllers can boot the array, everything else would be crazy. Not bootable = three hard drives required for a RAID0 system. Would make more sense to use RAID5 and bootable controller.

If the drive type supports hot swap (SATA or SCSI), you can unplug one hard drive and the other will continue. This should trigger an alarm. Might just be a popup in Windows, but it should be a loud siren. This also breaks the array and you cannot just plug the drive back and sync the changes. The array needs to be rebuilt - all data transferred from working drive to the just inserted. The rebuild procedure might not be automatic - in fact I doubt it is. Adaptecs expensive AHA-3200S rebuilds RAID5 automatically, but not RAID1. When you initiate manual rebuild, you have a chance of selecting the wrong source drive and will thus overwrite your changes.

If the drive type does not support hot swap, you will need to shut down your computer. The RAID bios will complain about missing disk and you might need to press a key. A siren should also be heard. Whether or not the BIOS allows you to boot on a broken array probably varies from BIOS to BIOS. But you should have the option of converting the array to a single drive.

In either case, removing the drive is not a brilliant idea, as the rebuild process can take hours and you lose your data if the primary drive breaks down during the process. Assuming you do it once a week and it takes 3 hours - you have a 2% chance of losing all data should the primary drive fail. That is not a viable backup solution.

RAID1 alone is not a backup - it is a protection against drive failure.  If you want a good backup solution, plug the drive in as a secondary drive once a week and make an incremental backup or sync the drive with rsync - it is avalible for Windows. An external drive (USB, Firewire, 2nd PC) is preferable, as a major power surge in the PSU can kill everything in the computer. Might also kill USB/firewire drives, but not a 2nd networked PC.

Onboard RAID1 questions

Reply #2 –
Thank you for your comments.

Quote
This also breaks the array and you cannot just plug the drive back and sync the changes. The array needs to be rebuilt

Ok, if the array needs to be fully rebuilt each time, probably raid1 is not what I should use.

Quote
An external drive (USB, Firewire, 2nd PC) is preferable, as a major power surge in the PSU can kill everything in the computer

I plan to use a regular hard drive monted in an extractible rack. Should be faster than an USB connection (no firewire), less expensive.
It is however slighlty less convenient. I need to put my computer in hibernation mode before insterting the hard drive (paralled ATA). (I am using hibernation for this as it is faster than a plain reboot, and is way more convenient)


The question is now how to conveniently sync 2 drives (including system installation). Rsync needs 2 computers, so it's probably not the right solution.
A backup software is not the proper solution neither, as it does not duplicate the system.


(perhaps the topic title should now be "using hard drives as a backup solution")

Onboard RAID1 questions

Reply #3 –
rsync does not need two computers, but it is for files only and will backup system configuration.

WinXP has a built-in backup system (based on BackupExec IIRC). It can be found under Accesories -> System Tools -> Backup. You might want to use a floppy to save Automated System Recovery information. I have not tried it, but I believe you can do a restore with the WinXP CD, the floppy and the 2nd hard drive which contains the backup files.

Using incremental backups, you can restore files from a specific date. Only problem is, that it does not keep track of deleted files (at least so I think). So if you deleted a lot of files, they will be restored during a full+incremental restore.

Another option is to clone the disk with a clone tool. There are two ways of cloning: 1. Clone entire disk (slow if you have big drives with much free space). 2. Files only (very time consuming with big drives with many files and little free space).

Norton Ghost and a Win98 boot disk can clone either way. But Ghost is not free,

A linux boot disk can do method 1 with the command like  dd if=/dev/hda of=/dev/hdc  (but you should know what you are doing...)

The good thing about a cloned disk, is that you can just plug it in and boot it.

Onboard RAID1 questions

Reply #4 –
Have a look at the cards by 3Ware, if you want a good IDE hardware card. Redhat has built in support too.
flac > schiit modi > schiit magni > hd650

Onboard RAID1 questions

Reply #5 –
I do not want prevention against file deletion, but against hardware failure.
This means that in this case, a backup on the second drive is useless: if the first drive is dead, I would need to buy a new one to be able to restore backup data stored on the second drive.

I would prefer a cloning solution. When I initially thought about raid1, it was mainly to achieve a transparent cloning.
A solution would be to use something such as Ghost to clone partitions, but it seems to me that such tools can not be run under windows ( NT5 in my case), so it would mean that if the drive is big, the computer will be innaccessible during a (relatively) long time. (I consider it to be innacessible while it is in dos mode)

Onboard RAID1 questions

Reply #7 –
Quote
I do not want prevention against file deletion, but against hardware failure.

In that case you should go with RAID1 without removing the disk every week. The chance of a power surge is next to zero compared to the chance of accidental file deletion, system curruption, virus, etc.

Cloning with Ghost can take hours, but maybe you sleep once a week :)

Seriously the incremental backup is quite good and will run in the background. If a disk dies, you will need to buy a new one anyway, and they are really not that expensive -- and maybe you are lucky and they live for years.

I am paraniod about backup myself.

Onboard RAID1 questions

Reply #8 –
Quote
a backup on the second drive is useless: if the first drive is dead, I would need to buy a new one to be able to restore backup data stored on the second drive.

Not with mirrored drives. Either one of the drives can be completely dead, and the machine is still up, still running, and the good drive is still accessable.
flac > schiit modi > schiit magni > hd650

Onboard RAID1 questions

Reply #9 –
Quote
Not with mirrored drives. Either one of the drives can be completely dead, and the machine is still up, still running, and the good drive is still accessable.

Could you possible read the thread and not repeat what has already been stated.

Thanks.

Onboard RAID1 questions

Reply #10 –
Buy a surge protector and go RAID 1 -> RAID 5 requires more disks (mimimum of 3 in use) , more expensive controllers, and array rebuild time is longer.

  The Tech-Report
had an article that compared 4 channel IDE RAID cards - the cheapest model (Highpoint RocketRAID133) did extremely well in comparison to the competition (3Ware, Adaptec,  Promise).
  I have had good experiences with on-board Highpoint RAID (HPT370/372) controllers myself, and the add-in cards from both them and Promise are reasonably priced.

  If you're super paranoid, you can buy three drives and make a RAID 1 array, then pull one of the drives and rebuild with the third, keeping the pulled drive in an anti-static bag in a climate-controlled safety deposit box in a high-elevation bank of your choice. Even if your house burns down, assuming you still live, you will have your data intact  B)
  It will also be both more straightforward and more redundant than software solutions.
Quote
But is it possible to boot on such a raid1 array

Every onboard RAID controller that I have used allows you to boot to the array - I have not used the new in-southbridge Intel and Via soft-'controllers', but I see no reason why they would be any different.

Onboard RAID1 questions

Reply #11 –
Quote
Quote
I do not want prevention against file deletion, but against hardware failure.

In that case you should go with RAID1 without removing the disk every week. The chance of a power surge is next to zero compared to the chance of accidental file deletion, system curruption, virus, etc.

I've had two failed drives, one virus attack, and three corrupted filesystems in the last five years. No power surges yet, thankfully. My point is that RAID1 would not have helped me in 2/3rds of my data loss situations, if I'm correct in thinking that both drives would have been corrupted had I been running RAID when my filesystem went kaput. Judging from my experience, RAID1 is good for getting maximum system uptime, but it isn't a very effective backup solution. For backups, you would probably be better off with one of sshd's previous suggestions (offline disk image or incremental backup).

By the way, I think most drive image programs are smart enough to skip over blank space on a disk. Powerquest Drive Image is, at least, and I'm pretty sure you can image a 40GB hard drive with Ghost using an image stored on a single CD. Cloning a 20GB partition with 2GB of data should take no more time than cloning a full 2GB partition.

Onboard RAID1 questions

Reply #12 –
Quote
My point is that RAID1 would not have helped me in 2/3rds of my data loss situations, if I'm correct in thinking that both drives would have been corrupted had I been running RAID when my filesystem went kaput

You are indeed correct - RAID 1 would have merely given you two redundant corrupted file systems.
Here it appears that Gabriel is concerned about loss via hardware failure, something that mirroring could indeed prevent, as could Ghosting, etc.
However, the cost of Norton Ghost in retail is probably pretty close to the cost of a new 40GB hard drive one could keep in the closet in a bag. I suppose the viability of any given method is dependant on Gabriel's budget...

Onboard RAID1 questions

Reply #13 –
Quote
Is it possible to remove one of the drives (for electrical safety reasons) and to only plug it weekly to synchronize data ?

Why not try one of these...

CMS Backup Solutions

All you do is plug in via USB or FireWire and it automatically starts a duplication.  If your main HD fails you can break open the enclosure, pull out the HD, and put it in your PC.  They even have models that come with FireWire or USB 2.0 PCI cards.

Since it instantaneously and automatically writes data to both drives, mirroring, or RAID 1, will (as said elsewhere) duplicate bad files, viruses, etc.

Onboard RAID1 questions

Reply #14 –
Quote
Cloning a 20GB partition with 2GB of data should take no more time than cloning a full 2GB partition.

I had the pleasure of partition-cloning a 80 Gb drive with 5 Gb data from Exchange. There were one huge 4 Gb file and MANY small ones. It took 9 hours...

The alternative was to clone all 80 Gb raw data. Unfortunately I did not have another 80 Gb drive, but I had plenty of networked space. It took 20 minutes to generate a 2 Gb file and then Ghost asked for next volume (pressing enter was required). That was not a viable solution.

Onboard RAID1 questions

Reply #15 –
Let me redifine my needs:

I would like to have a backup of my data, and also preserve it in case of power disaster. The constraints are ease of use and price. Ease of use means (in my case) that the process should mostly automated. Preferably the solution would be usable while the OS is loaded. In this case it could be scheduled to be runned while the computer is on (it is switched off during night and while no one is there)

The proposed solutions:

*raid-1
Does not cost that much compared to some other solutions if done in software. Thought that I could only occasionnaly plug the second disk in order to reconstruct the mirror. Problem is that it appear that reconstruction should be done at boot, paralising the computer during a significant time.

*backup to cdrw
Cost much than 2 hard drives, as I need the space to store backup, and the additional drive to restore data in case of original drive failure. Not easy to use as it requires a huge number of cdrw.

*backup to second hard drive.
Problem is that in case of failure, I would need a third hard drive to restore the data stored on the backup drive.

*CMS Backup Solutions
Seems to be able to mirror drive to external drive. Problem is that it is coslty. Advantage is that computer is still usable during mirroring process.

*cloning of partition:
Cheap, only 1 extra drive needed that will be re-used in case of failure of the first drive. Problem is that dd or ghost need to immobilize the computer while cloning.


In my ideal solution, I would occasionnaly plug the second drive, and mirror partitions while the OS is loaded.

Onboard RAID1 questions

Reply #16 –
Quote
The constraints are ease of use and price. Ease of use means (in my case) that the process should mostly automated. Preferably the solution would be usable while the OS is loaded. In this case it could be scheduled to be runned while the computer is on (it is switched off during night and while no one is there)

The methods can be combined to fulfill your needs, if you are willing to sacrifice 2-4 Gb storage.

Cloning + WinXP backup:

* Partition your hard drive into a system partition (around 2-3 Gb) and a data partition (the rest). Only Windows and a few essential apps are to be installed on the system partition.

* Do a one time clone of the master drive to the backup drive. You can now boot Windows on the backup drive.

* Once a week: Perform a full backup of the system partition and Windows settings with the built-in WinXP backup. It runs in the background. Save the backup file on the data partition on the master drive (not the backup drive).

* Insert the backup drive and sync the data partition from master drive to backup drive. rsync is excellent for this purpose, but xcopy can probably get the job done. This can also be done in the background - there should be no exclusive file locks on the data drive.  Remove the backup drive.


In case of a drive failure you can restore your system without a third disk (you are screwed if the backup drive fails though):

* Replace broken drive with backup drive and boot Windows. This will be a very old version of Windows - from the day you created the one time clone.

* Run built-in WinXP backup and restore the system partition from the backup file stored on the data partition. Reboot and you are up and running again with no more than a week's data loss.

Onboard RAID1 questions

Reply #17 –
Btw, if someone needs to clone a partition while running windows, it seems that DrvClonerXP could do the job.

Onboard RAID1 questions

Reply #18 –
What about an incremental backup system?
At least that usually can handle virus..

Onboard RAID1 questions

Reply #19 –
Incremental backup needs the storage space to back up and the storage space to restore, so overall you need 3 times your actual storage space.

The process proposed by sshd could be suitable for me. Until now, it seems to most interesting (according to my needs).
The only drawback is the potential power surge destruction while the 2 drives are simultaneoulsy in the computer.

Onboard RAID1 questions

Reply #20 –
Quote
Quote
Not with mirrored drives. Either one of the drives can be completely dead, and the machine is still up, still running, and the good drive is still accessable.

Could you possible read the thread and not repeat what has already been stated.

Thanks.

With 4 posts, I don't think you qualify as a moderator here.
flac > schiit modi > schiit magni > hd650

Onboard RAID1 questions

Reply #21 –
may not apply, cuz of windows, but I recall reading this some time back and thought it was a pretty good trick. I'm too lazy ot re-read it all again right now and figure out if it could be made windows-friendly too though, hehe. http://www.mikerubel.org/computers/rsync_snapshots/

Onboard RAID1 questions

Reply #22 –
Quote
With 4 posts, I don't think you qualify as a moderator here.

Let's hold off on the newbie bashing, Indybrett.

Gabriel, is the backup system for a mission-critical computer? Unless you can't afford even a few hours of downtime, I think you may be putting too much emphasis on the speed of getting your system up and running again after a drive crash. Let's say you use two drives and are running either incremental backups or disk images, and your main hard drive bites the dust. Some hard drive manufacturers will do an advanced replacement RMA, where they ship you a new drive as soon as you report a broken one, so you'll have your drive back in a couple days. Meanwhile, you can load the individual files you need from your backup drive onto another computer and continue your work. Drive Image's disk images can be browsed in Windows like an Explorer tree, and I think Microsoft's backup utility can do the same thing with its backups, so it's not like your data is inaccessible until you have an empty drive available to re-image. Assuming you can find another computer to use temporarily, which shouldn't be too hard this day and age, your downtime will only be a couple of hours.

Don't get too fixated on the problem of "triple storage" for non-RAID solutions. Most likely (and most fortunately), you'll never even need a third drive, because your system will always be up and running!

Onboard RAID1 questions

Reply #23 –
Quote
I had the pleasure of partition-cloning a 80 Gb drive with 5 Gb data from Exchange. There were one huge 4 Gb file and MANY small ones. It took 9 hours...

What program/version were you using? Using Drive Image 5.0, my 58,000-file, 44GB partition averaged over 300MB/min when I grabbed its image in DOS, about the same speed as my other partitions. Are we talking about millions of files? I wouldn't expect decent disk imaging programs to be so darn slow and useless.

Onboard RAID1 questions

Reply #24 –
Quote
Gabriel, is the backup system for a mission-critical computer? Unless you can't afford even a few hours of downtime, I think you may be putting too much emphasis on the speed of getting your system up and running again after a drive crash. Let's say you use two drives and are running either incremental backups or disk images, and your main hard drive bites the dust. Some hard drive manufacturers will do an advanced replacement RMA,


No, it is not for a mission critical system (otherwise I would use some kind of triple storage).
The problem is the cost. It is likely that the main drive will fail after the warranty period. In this case, I will not have any replacement drive from the manufacturer. So it would mean buying a new drive.

In any way I will have to buy a new one in case of failure, but I would prefer having the system up quickly. It would take several days to have the system running again. In the meantime, a lot less music, no more internet access (would need to set it up on the laptop), no more tv,....

As the storage space for backup and cloning is about the same, why not duplicating the system?
I see no real advantage on backup.