On Thursday, 20 March 2003 at 13:13:18 +0100, Alexander Haderer wrote: > At 12:53 20.03.2003 +0100, Maarten de Vries wrote: >> This would be for backup. Data on about 50 webservers would be backed up >> to it on a nightly basis. So performance wouldn't be important. > > Sure? Consider this: > > a. > Filling 3TB with 1 Mbyte/s lasts more than 800 hours or 33 days.
I do a nightly backup to disk. It's compressed (gzip), which is the bottleneck. I get this sort of performance:
dump -2uf - /home | gzip > /dump/wantadilla/2/home.gz ... DUMP: DUMP: 1254971 tape blocks DUMP: finished in 217 seconds, throughput 5783 KBytes/sec DUMP: level 2 dump on Thu Mar 20 21:01:31 2003
You don't normally fill up a backup disk at once, so this would be perfectly adequate. I'd expect a system of the kind that Maarten's talking about to be able to transfer at least 40 MB/s sequential at the disk. That would mean he could backup over 1 TB in an 8 hour period.
Of course you are right. My note a. was meant as a more general hint to think about transfer rates when dealing with large files/filesystem. Maarten gave no details about how the webservers are connected with the backup server. I should have give more details of what I mean: When backing up 50 Webservers over network to one backup server the network may become a bottleneck. If you have to use encrypted connections (ssh) because the webservers are located elsewhere you need CPU power at server side for each connection.
> b. > Using ssh + dump/cpio/tar needs CPU power for encryption, especially when > multiple clients safe their data at the same time.
You can share the compression across multiple machines. That's what was happening in the example above.
It is a good idea to do compression at the client side.
As I understand your example /dump/wantadilla/2 is either a local dir or connected via NFS. The latter requires a local network if you don't want to do NFS mounts across the Internet. Is this right?
with best regards
Alexander
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Alexander Haderer Charite
Campus Virchow-Klinikum
Tel. +49 30 - 450 557 182 Strahlenklinik und Poliklinik
Fax. +49 30 - 450 557 117 Sekr. Prof. Felix
Email [EMAIL PROTECTED] Augustenburger Platz 1
www http://www.charite.de/rv/str/ 13353 Berlin - Germany
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