[Dirvish] c't article - USB drives, mysql, translation help please?

Roel Schroeven rschroev_nospam_ml at fastmail.fm
Sat Jun 10 22:53:31 UTC 2006


Keith Lofstrom schreef:
> I have done a very crude translation of the c't article, and 
> there are two topics that I could not translate correctly that
> appear important.  Can any of our German colleagues help?

I don't speak German, but I speak Dutch and I have a subscription to the 
Dutch version of c't, which is mostly just a Dutch translation of the 
German version.

> The first is on page 214, column 4, discussing mysql .  I assume
> this is about preparing a mysql database for backup?  Could someone
> translate those paragraphs?

The page numbering is different of course; I don't even have that many 
pages.

What they're saying about mysql is just that you can't just copy the 
files on disk, since can't assume that there is a current or even 
consistent version of the data on the hard disk at the time of backup. 
Therefore you need a special tool to create a snapshot. They show a 
shell script that uses mysqldump to create the snapshot and uses find 
with rm to delete old snapshots.

You can run the mysql backup script from /etc/dirvish/dirvish-cronjob, 
directly via cron, or via post-server in default.conf:

post-server: ; /usr/local/bin/mysql-backup.sh $DIRVISH-DEST/../mysql

in a vault's default.conf will produce a copy of the database in each 
snapshot of the vault. In that case you need to comment the find command 
in the backup script.

To backup a databases on an external server, you can specify the 
hostname with -h.

> The second is on page 215, the bottom of column 1 and the top of
> column 2, discussing external USB hard drives, some problem with
> sleep mode?

According to the article: USB hard drives have one disadvantage: even 
though the ATA disks in those drives support sleep modes, in practice 
those modes can't be used since the ATA adapters only support a very 
limited command set, and the standby commands tend not to be part of it. 
Since you don't want to switch the hard drive on and off manually if 
it's part of an automated backup, that means that the hard drive is 
continually on and hence continually consumes power and makes noise. 
Also, because of the USB hotplug mechanism the device names or not 
always the same.

To prevent all that misery, you can add a second ATA disk into the 
system and attach it as master to the secondary ATA controller. etc. etc.

HTH

-- 
If I have been able to see further, it was only because I stood
on the shoulders of giants.  -- Isaac Newton

Roel Schroeven


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