offsite system backup for HP Proliant server

Hello Experts,

BACKGROUND
I have a HP Proliant ML150G5 server.  I've configured it as a file server using Suse Linux Enterprise Server version 10.

The server has two 146GB SAS Hotplug Hard Drive configured as RAID 1+0. Since there are only 2 harddrives, correct me if I'm wrong, in effect, this is just RAID 1 (mirroring).
The server is working well so far and we're happy with it.

QUESTION
Now the question.
I would like to have an offsite system backup, so that in case something goes wrong with the OS (say, I accidentally delete some system files), I could bring up the system without having to re-construct all the hardware and software settings.

Assumption: Apart from the system backup, I will keep a separate data back up in another disk or machine.

I see 3 possibilities here.

OPTION 1
Given
        2 plugged SAS harddrives labeled A & B (current setup)

Unplug drive B and keep it as an offsite system backup. (Since my RAID setting is mirroring, I suppose I can do this without shutting down the server.)

If something goes wrong with Drive A (hardware error) or something goes wrong with the OS, I can still rebuild the system by unplugging Drive A then plugging in Drive B (to the same bay from which I got it from).

Disadvantages of this scheme:
1. There will be an additional downtime for getting Drive B  into the office.
2. Update of data in Drive B (from the data backup )may take some time since it will be quite old.


OPTION 2
Buy another harddrive (of the same specs as the existing ones). Use this spare harddrive to swap with one of the two currently-installed harddrives every month.

Thus:

Given
        2 SAS harddrives labeled A & B
        1 extra SAS hardrive labeled C

Current Config
         Drive A is plugged in Bay 3
         Drive B is plugged in Bay 4
         Drive C is free, not plugged to server
After 1 month
          Hotswap Drives B and C  (Uplug Drive B & replace it with Drive C in Bay 4)
          keep Drive B as offsite backup
After another month
          Hotswap Drives C and B (Uplug Drive C & replace it with Drive B in Bay 4)
          Keep Drive C as offsite backup
After another month
          Hotswap Drives B and C  (Uplug Drive B & replace it with Drive C in Bay 4)
          keep Drive B as offsite backup
and so on...

In other words,
         Drive A stays in Bay 3 while Drives B & C alternate occupying Bay 4, the one which is not plugged is kept as an offsite system and data backup.

Advantages of this scheme:
1.  If one of the plugged harddrives fail, the system is still up (no downtime)
2.  If both currently plugged drives fail, the system can be rebuilt from the offsite backup
3. since the offsite backup will be at most 1 month old, the update of data (from the data backup) will be much faster than in Option 1.

OPTION 3
Get a 3rd harddrive, plug it in an empty bay, make it mirror the 2 existing drives, then unplug it to keep it as an offsite backup.
I'm not sure if this is possible with the RAID 1+0 setup (or for other RAID setups for that matter).   If it's possible, i would appreciate getting instructions on how to set it up, given that I already have 2 harddrives setup as RAID 1+0.

Advantages of this scheme:
Same as in Option 2 plus: Drives A & B remain in tact in the server

BOTTOM LINE
I wish to know which of the 3 options above would be best. Or perhaps you can suggest a better solution.  Just to repeat myself: What I basically want is an offsite system backup such that if, something goes wrong with the OS (or the haddrive) I can easily reconstruct the server.

In Windows desktop machines, I easily do this using a disk cloning/imaging.  I'm basically trying to look for its equivalent in a RAID-setup, linux-installed, server.

Would appreciate your help.

Thanks in advaced,
newind
newindAsked:
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sukamtoCommented:
Option 1 is bad choice, with only 2 hdd and you unplug 1 for offline spare, you have no fault tolerance on existing raid 1.

Option 2 is the good choice, rather than waiting for 1 month actualy you can exchange hdd B and hdd C every weekend, its better.

My option is, if you still enough budget or rather than buy expansive SAS Hotplug hdd, you can buy Acronis backup & recovery for linux server around $900 (http://www.acronis.com/backup-recovery/server-linux/) and a cheap external USB 1TB, then you can do online backup everyday to external hdd (full backup or additional/differential). Not just OS / hardware issue, in case of virus or unintentionaly deleted file/folder of users, you can recover it online from ext hdd.
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newindAuthor Commented:
Thanks for the reply sukamto.

Questions:
1. So you think Option 2 does not have any issues? I was given this feedback from another forum, any way to resolve it?

"Option2 is a good idea except with one caveat. It will work fine the first month but the second month the spare disk already contains raid information on it, so when you plug it in, the raid controller will read it as a raid disk and will not sync drive A to it. You have to find a way to erase the disk before puting in the server."

2. About your suggestion, does acronis support SAS harddrives?
3. I actually have 2 servers, one is a file server and the other a mail server. Do I need to get a license for both?
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sukamtoCommented:
1. That is true if you plug in the hdd while server is offline (server power off), so to prevent this issue, you MUST plug in the hdd while the server is still online / powered ON then HP Smart Array (Raid controller) will detect it as replacement disk and automaticly start the rebuild process. The only short coming is, every time you change the hdd, the process rebuilding will taking place and take from minutes to hours to finish depend on your hdd size, so while the rebuild time your server does not have fault tolerance on hdd until the rebuilding process completed on that just plugged in hdd.

2. yes, it support SAS, SCSI, IDE.

3. yes, acronis license is server based, each server installation of acronis will need a license.
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newindAuthor Commented:
Hello again sukamto,

Final questions before I reward the points:

1.  Would you mind giving feedback on the following comment (re Option 2) from the other forum?

"I can not confirm the offline/online cases. I would expect that the controller will read the inserted disk the same way whether it is inline or offline. It will see the previous raid configuration on it and would treat it as a raid disk and not as an unused disk to start the rebuild."

2. Do you think Ghost can do the imaging of the RAID disks to another external harddrive?

Thank you so much for your time.
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sukamtoCommented:
"I can not confirm the offline/online cases. I would expect that the controller will read the inserted disk the same way whether it is inline or offline. It will see the previous raid configuration on it and would treat it as a raid disk and not as an unused disk to start the rebuild."
=> i dont think so, when you pull out 1 hdd, raid will detect 1 hdd failed and remaining hdd will still functioning as usual, right? then if we plug-in 1 hdd ( new or old or previous same raid hdd ), as long as it is a good hdd, raid card will detect it as "previously failed hdd is replaced", it wont check for its content or raid conf inside because the system is just still up meaning current raid conf is still there - online, no need to check hdd for raid conf, it just purely detect as new hdd plug in and automatic begin the rebuilding process. it is different when you plug in offline (server shutdown), on boot up raid card will check hdd for raid conf, because there are 2 hdd with same raid conf but not synchronized, probably raid card will confused, which one should be the master / source to begin the rebuilding / sync process.


2. Do you think Ghost can do the imaging of the RAID disks to another external harddrive?
=> depend on your ghost version, as long as your ghost able to detect & provide your raid card, it will able to detect your sas raid array then you can image it as usual. simple way, try boot up with your ghost cd, if you able to detect the raid 1 disk (raid 1 array), then it is consider working.
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newindAuthor Commented:
Thank you very much sukamto for your time and effort.
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newindAuthor Commented:
Hello again,

I was given this excellent link which contains some really good information for splitting and combining mirrors.  

http://bizsupport1.austin.hp.com/bc/docs/support/SupportManual/c00378986/c00378986.pdf
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sukamtoCommented:
Great.
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