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02-21-2012 03:35 AM
02-21-2012 03:35 AM
Hello Forum,
Is that possible to backup a raw file system on HPUX 11iv1? maybe by copying the data to another disk.
For the vxfs file system we can use the command copy, shall I use the command dd for the raw file system ?
Did anyone try it before?
Thanks.
Solved! Go to Solution.
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02-21-2012 06:39 AM
02-21-2012 06:39 AM
SolutionWhat kind of data does the "raw file system" contain?
If it's e.g. an Oracle database, it would be better to use the appropriate database backup/restore tools for that database.(RMAN? Full export? You should ask your DBA to suggest a good solution.)
When you have a dd-type backup, your only option is to completely restore the whole raw disk/LV; with a proper database backup, it is easy to restore only selected parts if a full restore is not needed (for example, if you only need to restore one accidentally-deleted table whose name is known).
If you want to backup a database with dd, the database should be shutdown (or set in backup mode) while dd runs. Otherwise there is a risk that something might be written to the database while dd is running; if one part of the write operation changes already-backed-up data and another part changes something that dd has yet to copy, your backup will be corrupted, as it will contain a random mixture of data from "before" and "after" the write operation.
A "dd" backup will always be the full size of the raw file system, and it must be restored to a disk/LV that is at least the same size: any less and there is a risk that some important data will be truncated. If you restore a "dd" backup to a disk/LV that is larger than the original, the extra capacity is likely to be wasted, unless there is some application-specific method to tell the application to start using the extra space.
If you have no other suitable tools and you can shutdown the database/application for backup, it is possible to use dd. But I strongly suggest using some other tool that is more appropriate to whatever is inside your raw filesystem.
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02-21-2012 02:40 PM
02-21-2012 02:40 PM
Re: Backing up a raw file system
I largely agree with Matti, but best I know you _can_ pipe DD output from a raw into a compress too (like zip/bzip2/gzip -c) and visa versa.
That way the file can be a lot smaller than then raw device, notably if the raw device was intiallized with all zeros before use (dd if=/dev/zero of=...).
Also, be sure to use a large blocksize on the dd. For example bs=1m
hth,
Hein
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02-22-2012 03:13 AM - edited 02-22-2012 03:15 AM
02-22-2012 03:13 AM - edited 02-22-2012 03:15 AM
Re: Backing up a raw file system
Hi:
Sample copy with "ssh"
dd if=/dev/vgoracle/rlvol1 bs=64K| ssh node2 "dd of=/dev/vgoracle/rlvol1 bs=64k"
rgs,