Linux Storage system: looking for advices Post: 302385670

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Special Forums Hardware Filesystems, Disks and Memory Linux Storage system: looking for advices Post 302385670 by Loic Domaigne on Saturday 9th of January 2010 03:07:36 AM

01-09-2010

Registered User

Quote:

Originally Posted by pludi

Which is, usually, something you do not want to happen. Personally, I'd rather have a system that's a bit slower if a disk goes bad, but keeps on working, than losing files and not being able to use the system until I've got a replacement disk. But that might just be me.

I agree that the requirements look a bit wired. The important data are backup on an external NAS, so it would (theoretically) "be acceptable to loose the data on the failed drive". But if one can afford to loose the data on the drive, why put it there in the first place?

Quote:

Originally Posted by Loic Domaigne

However, I failed to restore the file system if /dev/vda6 gets damaged. I used an alternate superblock for fsck (one located on vdb2 or vdb3), but no avail.[...]

Quote:

Originally Posted by pludi

That might be because of the striping done by LVM. The volume manager doesn't fill up the first disk, then the second, and so on, but first fills the first stripe (by default 4 MB) on the first disk, the first stripe on the second disk, and so on. With that scheme it might very well be that all superblocks end up on the same disk.

Actually, the restore operation has succeeded. What failed: I lost the filenames and directory contents, the files were restored in lost+found. The reason for this behavior is quite simple: directory contents are stored on data block, and if this block is gone (as it was the case in my scenario), then you loose this information forever. One more reason for RAID+LVM.

Thanks you everyone, and especially pludi

. I gathered enough information to make a sound proposal for the storage system!

Loic Domaigne

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LEARN ABOUT CENTOS

amzfs-sendrecv

AMZFS-SENDRECV(8)					  System Administration Commands					 AMZFS-SENDRECV(8)

NAME

       amzfs-sendrecv - Amanda script to create zfs sendrecv

DESCRIPTION

       amzfs-sendrecv is an Amanda application implementing the Application API. It should not be run by users directly. It create a zfs snapshot
       of the filesystem and backup the snapshot with 'zfs send'. Snapshot are kept after the backup is done, this increase the disk space use on
       the client but it is neccesary to be able do to incremental backup. If you want only full backup, you can disable this feature by setting
       the KEEP-SNAPSHOT property to 'NO'. Only the restoration of the complete backup is allowed, it is impossible to restore a single file.

       The application is run as the amanda user, it must have many zfs priviledge:

	   zfs allow -ldu AMANDA_USER mount,create,rename,snapshot,destroy,send,receive FILESYSTEM

       Some system doesn't have "zfs allow", but you can give the Amanda backup user the rights to manipulate ZFS filesystems by using the
       following command:

       usermod -P "ZFS File System Management,ZFS Storage Management" AMANDA_USER
       This will require that your run zfs under pfexec, set the PFEXEC property to YES.

       The format of the diskdevice in the disklist (DLE) must be one of:

       Desciption	       Example
       ----------	       -------
       Mountpoint	       /data
       ZFS pool name	       datapool
       ZFS filesystem	       datapool/database
       ZFS logical volume      datapool/dbvol

       The filesystem doesn't need to be mounted.

PROPERTIES

       This section lists the properties that control amzfs-sendrecv's functionality. See amanda-applications(7) for information on the
       Application API, application configuration.

       DF-PATH

	   Path to the 'df' binary, search in $PATH by default.

       KEEP-SNAPSHOT

	   If "YES" (the default), snapshot are kept after the backup, if set to "NO" then snapshot are no kept and incremental backup will fail.

       ZFS-PATH

	   Path to the 'zfs' binary, search in $PATH by default.

       PFEXEC-PATH

	   Path to the 'pfexec' binary, search in $PATH by default.

       PFEXEC

	   If "NO" (the default), pfexec is not used, if set to "YES" then pfexec is used.

EXAMPLE

       In this example, a dumptype is defined to use amzfs-sendrecv application to backup a zfs filesystem.
	define application-tool amzfs_sendrecv {
	  comment "amzfs-sendrecv"
	  plugin "amzfs-sendrecv"
	  #property "DF-PATH"  "/usr/sbin/df"
	  #property "KEEP-SNAPSHOT" "YES"
	  #property "ZFS-PATH" "/usr/sbin/zfs"
	  #property "PFEXEC-PATH" "/usr/sbin/pfexec"
	  #property "PFEXEC" "NO"
	}

	define dumptype user-zfs-sendrecv {
	  program "APPLICATION"
	  application "amzfs_sendrecv"
	}

SEE ALSO

       amanda(8), amanda.conf(5), amanda-client.conf(5), amanda-applications(7)

       The Amanda Wiki: : http://wiki.zmanda.com/

AUTHOR

       Jean-Louis Martineau <martineau@zmanda.com>
	   Zmanda, Inc. (http://www.zmanda.com)

Amanda 3.3.3							    01/10/2013							 AMZFS-SENDRECV(8)