This is a bit of a newbie question and hope this is appropriate for this
list, so apologies in advance.
We are hoping (if funding is approved) to get a new server to replace an
old server currently in use. The server is primarily an NIS/NFS server
supporting a software development computing center. The current server has
kind of a hodge-podge of IDE and SCSI disks (no RAID) and a SCSI
multi-tape backup device, using amanda as the backup application. A
previous sys admin set up the user disk partitions on this server to be
around 20 GB to match a 20 GB holding partition for amanda.
The new server is planned to have a RAID 5 array with 4 disks plus 1
spare. The software base for this would be Linux (Debian woody) using a
recent 2.4.x kernel. We plan to use the software RAID facilities in
Linux, not a hardware RAID controller. My understanding of RAID is that
this would result in a single, large device -- /dev/md0. This is great and
I plan put all the user accounts on a filesystem on /dev/md0 and NFS serve
those to all the client machines (mostly Linux, some Sun) we have.
The thing I am confused about is how this will affect our amanda backup
strategy. The array size will be a little over 700 GB. To follow our
current amanda setup it seems that the RAID device should be split into
multiple partitions with one dedicated as a holding partition for amanda.
But I'm not sure this is possible or desireable with a RAID array.
Any ideas, comments?
Thanks...
On Wed, 3 Mar 2004, Steve Witt wrote:
We are hoping (if funding is approved) to get a new server to replace an
old server currently in use. The server is primarily an NIS/NFS server
supporting a software development computing center. The current server has
kind of a hodge-podge of IDE and SCSI disks (no RAID) and a SCSI
multi-tape backup device, using amanda as the backup application. A
previous sys admin set up the user disk partitions on this server to be
around 20 GB to match a 20 GB holding partition for amanda.
If you only have one server, and one tape drive, you don't really need the
holding partition..
The new server is planned to have a RAID 5 array with 4 disks plus 1
spare. The software base for this would be Linux (Debian woody) using a
recent 2.4.x kernel. We plan to use the software RAID facilities in
Linux, not a hardware RAID controller. My understanding of RAID is that
this would result in a single, large device -- /dev/md0. This is great and
I plan put all the user accounts on a filesystem on /dev/md0 and NFS serve
those to all the client machines (mostly Linux, some Sun) we have.
You can split the disks and have smaller partitions - I've done this
myself in the past with good results. Eg. on the 5 disks, give each of
them an identical partition table of (eg)
512MB /
1024MB swap
1024MB /usr
Rest of disk /var
then make the raid5 arrays out of the same slices on each disk. (Although
/ can only be on RAID1, so you "waste" 3 partitions).
I have several servers similar to this and run amanda on them.
The thing I am confused about is how this will affect our amanda backup
strategy. The array size will be a little over 700 GB. To follow our
current amanda setup it seems that the RAID device should be split into
multiple partitions with one dedicated as a holding partition for amanda.
But I'm not sure this is possible or desireable with a RAID array.
Amanda doesn't work very well when the disk partition is larger than your
tape size. If you don't have remote servers to backup, you don't need a
holding partition at all. (Although you need to specify one to keep it
happy, but then you can mark each data partition as "holding disk" to stop
them being copied to the holding partition which is just a waste of time
on the server).
You might need to split the partitions into ones just about the size of
your tapes. Get the biggest tape you can afford, and then work out how
much you realistically expect your data to compress. Do not belive the
tape makers claims of x2 compresion, in the real world, it just doesn't
work that way.
Gordon
On Wed, 3 Mar 2004 at 9:35am, Steve Witt wrote
The thing I am confused about is how this will affect our amanda backup
strategy. The array size will be a little over 700 GB. To follow our
current amanda setup it seems that the RAID device should be split into
multiple partitions with one dedicated as a holding partition for amanda.
But I'm not sure this is possible or desireable with a RAID array.
You don't have to do that. Lines in amanda's disklist need not be
partitions as long as you use tar as the backup tool. You can play all
sorts of tricks with includes and excludes as well. Search the amanda
mailing list archives for all details on this, or look in the sample
disklist included in the amanda tarball for examples. I currently backup
5.5TB worth of formatted space (4 partitions) to 2 AIT3 drives with
amanda.
--
Joshua Baker-LePain
Department of Biomedical Engineering
Duke University