I currently have two CentOS servers. I need to know how and what the quickest way would be to "tar" up the images directory and SCP it over?
Is that the quickest way that I just suggested, because tarring is taking forever... I ran the command:
tar cvf imagesbackup.tar images
And I was going to just scp it over.
Let me know if there is a quicker way. I have remote/SSH access to both machines.
Instead of using tar to write to your local disk, you can write directly to the remote server over the network using ssh.
Any string that follows your "ssh" command will be run on the remote server instead of the interactive logon. You can pipe input/output to and from those remote commands through SSH as if they were local. Putting the command in quotes avoids any confusion, especially when using redirection.
Or, you can extract the tar file on the other server directly:
Note the seldom-used
-Coption. It means "change to this directory first before doing anything."Or, perhaps you want to "pull" from the destination server:
Note that the
<(cmd)construct is new to bash and doesn't work on older systems. It runs a program and sends the output to a pipe, and substitutes that pipe into the command as if it was a file.I could just have easily have written the above as follows:
Or as follows:
Or, you can save yourself some grief and just use rsync:
Finally, remember that compressing the data before transfer will reduce your bandwidth, but on a very fast connection, it may actually make the operation take more time. This is because your computer may not be able to compress fast enough to keep up: if compressing 100MB takes longer than it would take to send 100MB, then it's faster to send it uncompressed.
Alternately, you may want to consider piping to gzip yourself (rather than using the -z option) so that you can specify a compression level. It's been my experience that on fast network connections with compressible data, using gzip at level 2 or 3 (the default is 6) gives the best overall throughput in most cases. Like so:
I'd be tempted to rsync it over myself - it does compression and handles link loss well.
If you just tar them up and nothing else this will waste tons of time with only minimal speed gain.
So simply taring up the files with the cvf switches will effectively cost the time it takes to read all the 55GB images and write them back to disk. (Effectively it will be even more time wasted since there will be an considerable overhead).
There is only one advantage you gain here, the overhead for uploading many files is being reduced. You might get faster transfer times if you compress the images (but since I believe they are already in a compressed format this won't be much help). Just more waste of computing time.
The biggest disadvantage from transfering a huge tar archiv over wire is that if something goes wrong it could mean you have to start over.
I would use that way:
On the new server
And then just
diff. And since scp supports compression on the fly there is no need for separate archives.Edit
I'll keep the MD5 information since it was useful to the OP. But one comment hit me with new insight. So a bit of searching provided this useful piece of information. Please note that the subject here is SFTP not directly SCP.
On top of Pacey's md5sum suggestion, I'd use the following:
On the destination:
nc -w5 -l -p 4567 | tar -xvf -Then on the source:
tar -cvf - /path/to/source/ | nc -w5 destinationserver 4567It's still a tar/untar, and there's no encryption, but it's direct to the other server. Start them both in tandem (
-w5gives you 5 seconds' grace.) and watch it go. If bandwidth is tight, add -z to the tar on both ends.One point - not all hosts have rsync and may hosts may well have different versions of tar. For this reason, one could recommend as a first port of call using the oft-neglected cpio.
You can cpio over ssh to do ad-hoc replication of file/directory structures between hosts. This way you have finer control over what gets sent over seeing as you need to "feed" cpio, nom-nom. It's also more argument-portable, cpio doesn't change much - this is an important point if you are looking after multiple hosts in a heterogeneous environment.
Example copying /export/home and subdirs to remote host:
The above would copy the contents of /export/home and any subdirs to /export/home on the remote host.
Hope this helps.
I you have ssh access, you have rsync access.
or
If you receive an error like "rsync error: some files could not be transferred (code 23) at main.c(977) [sender=2.6.9]", check your user and groups between the servers; you might have a mismatch.
Use the rsync "-z" option if you want rsync to compress the transfer. This option will use more CPU but less bandwidth, so be aware of that.
There is a "--progress" option which will give you a percent transferred, which is kind of nice if you like that sort of thing.
Are they on a shared network instead of needing the internet to transfer files? NFS or FTP might be a lot faster than the overhead of SCP, although you would lose the encryption during the transfer.
Or you can always use tar pipes :
'j' = bzip2, you can use 'z' for gzip or --lzma if your tar supports it.