[rescue] Re: Tape backup and amanda questions

[Robert Novak]

On Sat, 9 Nov 2002, Tim H. wrote:

> I have just rescued a DEC TZ86 6G DLT drive

Woowoo. Good rescue.

> First of all, is amanda a good choice for backup?  I do want the
> capability to do remote backups, but I am a little concerned that it
> can't span disks with a single backup set. What other options should I
> look at (the server is an AlphaServer 400 4/166 running NetBSD)

I think you mean it can't span tapes? 

For multiplatform zero-dollars-expended-on-licensing backups, AMANDA is
probably the best prebuilt product. 

Yes, I'm being hedgy here. Some people will swear by scripting with native
utils or tar/cpio. If you were using a Linux server you could use the free
Arkeia Light version (supports OpenBSD and NetBSD clients now, 1 server
and 2 linux/bsd/windows clients for free).

> If I go with amanda how big a temporary disk do I need?  I am currently
> serving out of 2 9G drives.  

Bare minimum, you should have a disk that is as large as the compressed
size of your largest filesystem. Easiest way is to have a staging space
the size of your largest filesystem, and most optimal would be a staging
space that is the same size as all of your filesystems combined.

AMANDA will write the backup to disk, and then compress it directly to
tape. This optimizes compression and tape performance, which is
particularly important on DLT (as I recall). Streaming a network stream to
tape can cause rewinds and repositions which will wear the tape down and
reduce your capacity/performance. By feeding directly from a
hopefully-faster-than-tape disk, you can keep the tape going non-stop.

Also, you can run your backups without a tape in, and then amflush to tape
when you put a tape in. This is where the "optimal" option above comes in
handy. I used to do my backups of a small setup to a 36gb disk, and then
once a week I'd flush the weeklies to tape. 

As a data point, I first used AMANDA in a corporate setting with an Ultra
2 fileserver and a Mammoth tape drive. I got 50GB on a 20GB native tape
with gzip on the U2 host. Unfortunately, I had to give up on single-tape
architecture when my daily backups started taking 27 hours. :)

> And last, I have plenty of tapes but I will need to acquire a cleaning
> tape at some point.  How often do these drives need cleaning, where is
> the most affordable place to get a cleaning tape, and how many cycles
> is a cleaning tape good for?

I'd find the appropriate part number, or just guess at the name "dlt
cleaning tape" and search pricegrabber.com for starters. They probably
show up on ebay as well. I think Eric already gave 12 cleanings as a good
guideline.

Enjoy your new tape system.  I should get one of mine going soon, since
I'm kinda using a fileserver now. :)

Rob 

Robert Novak, Indyramp Consulting * rnovak at indyramp.com * indyramp.com/~rnovak
	"I don't want to doubt you, Know everything about you
      I don't want to sit Across the table from you Wishing I could run."