dd command on live system ?

maas187 · 02-23-2009, 03:49 PM

Hi to all, i have a windows 2003 server that has an external HD as RAID.

that Extenal HD is mounted on a linux system as well.

If i use a DD command to backup my RAID. to another external HD as an Image. would that destroy my RAID ? and if it did not give any errors would this Image be bootable ?

thank you.

Regards,
MaaS

acid_kewpie · 02-23-2009, 04:40 PM

it wouldn't affect it, no. It wouldn't be logically able to, as your /dev/md0 or whatever block device is the product of the raid, not the raid itself, so sits "above" it.

choogendyk · 02-23-2009, 07:56 PM

dd on a live system probably has the same shortcomings as dump on a live system. You indicate that it is an external drive for the 2003 system and mounted from the linux system as well. So, you're booting off the external drive? That's not clear, but you indicate you want to know if it will be bootable.

My gut reaction is that whether it would be bootable is a crap game, with the odds being worse if it is booted as 2003 when you dd it and you want the image to boot as 2003. Any inconsistencies would be related to how actively it is being modified as the dd read goes through the drive.

Typically, sysadmins get away with using dump in the middle of the night. But vendors always warn against doing it in active multi-user mode. You can increase your odds of success by using snapshots, but that doesn't really apply to dd.

maas187 · 02-24-2009, 01:45 PM

Quote:

Originally Posted by choogendyk

dd on a live system probably has the same shortcomings as dump on a live system. You indicate that it is an external drive for the 2003 system and mounted from the linux system as well. So, you're booting off the external drive? That's not clear, but you indicate you want to know if it will be bootable.

My gut reaction is that whether it would be bootable is a crap game, with the odds being worse if it is booted as 2003 when you dd it and you want the image to boot as 2003. Any inconsistencies would be related to how actively it is being modified as the dd read goes through the drive.

Typically, sysadmins get away with using dump in the middle of the night. But vendors always warn against doing it in active multi-user mode. You can increase your odds of success by using snapshots, but that doesn't really apply to dd.

yea what you said makes sence. usually its done at night. but the Server 2003 server if never off. the only reason why i back my 2003 RAID using linux is to keep a full backup of my server 2003 and its done everynight. Now if my 2003 crapped out. can i just use my backup to restore my 2003, and would i encounter any error's at boot, or even kernel errors ?

thank you for the reply everyone .