New subject: Non-streaming tape performance

15 Feb 2000


      A few mails condensed here:
On Tue 15 Feb, 2000, Jay Orr orrjl@stl.nexen.com wrote:
...
My understanding of Budtool and Quick Restore was that you could pull tar
files off of the tape directly. Generally, the desire for this ability is:

if the machine with the backup software goes down, you can still do

recoveries, and
2) you can restore to differing systems.
That was what used to be my line on tape formats too. Then I investigated
how Legato could be used in the case of the backup server itself dying.
The key is to know (have writtenfor yourself) a procedure for rebuilding
a backup server efficiently. I used to think Legato was a pain at this,
but it turns out that if you set up a server reasonably you can follow
their Disaster Recovery Guide and be back in business pretty quickly. In
about as much time as it would take you to find the right tapes somehow
and trawl them by hand using tar or dump/restore.  I'm assured ADSM and
Veritas and presumably everyone else as well has their own Way.
...
I will grant that the Veritas solution of interleaving streams does sound
well thought out and probably more efficient, but from an admin's
perspective, you have to figure some day the worst will happen.
AFAIK The interleaving thing was born of expediency, for all the backup
product vendors: for backing up from slow individual clients to tapes
that only work efficiently when streaming. Tape lifetimes are also
reduced sharply when tapes are constantly stopped, rewound-a-bit and set
to streaming again. The fact that most admins like to get their backups
done in the same windows, and using the same policies, relying on the
backup software to work at least some of it out for them, means many
backups get scheduled for the same time anyway. On a more banal note, is
it not tempting to set client-paralellism up a notch, it sounds sexy
and you never know, it *might* help.
...
Reminds me of Microsoft's argument against solaris : "Sun is trying to
resurrect the 1960s-era mainframe paradigm and return computing to
old-style timesharing." (www.dot-truth.com) Amazing how marketing appeals
to feelings, not empirical data.
Always the way. Often works too - like when vendors sell to managers
who don't then employ their technical staff in product evaluation and
selection cycles. Or worse, they do but it's all a shame exercise, which
means that the time was wasted on top of the bogus decision.. I'm not
bitter, really. 8)
...
Until the system with the backup-product fails....
Ah, well I refer to my point about having a good procedure for dealing
with that.
IMHO it's more important for business continuity to have the whole backup
service back than it is to get the first restore done - because Murphy
will most likely have the most restores you ever saw be requested in
that window, just after you decided that doing that one restore *then*
getting the backup system going again would be the best policy.
Been there. Got bitten.
...
But that all said, your comments are appreciated and gives me food for
thought. I guess it weighs in as one of the older Unix paradoxes - ease
vs. utility (can't think of a better way to phrase that). Sure, who
wouldn't want the easiest to use backup software? But from an admin
perspective, we have to be able to pick up the pieces if it all explodes
and put it back together ASAP.
Yup it's a balancing act - the two aren't necessarily mutually exclusive
goals though.
...
-- End of excerpt from Jay Orr
On Tue 15 Feb, 2000, Steve Kappel steve.kappel@raistlin.min.ov.com wrote:
...
Interleaving (multiplexing is the term in NetBackup) is optional in
NetBackup.  You can turn it off for any class.
This is good to know - though I guess you have to be confident of the ability
of a given client to supply data to keep the tapes fed.
...
NetBackup NDMP does NOT use multiplexing.  Also note that for NDMP
the tape format is determined by the NDMP server vendor.
NDMP uses dump format as well doesn't it? So all the propositions above
get a little messed around here anyhoo.
...
-- End of excerpt from Steve Kappel
On Tue 15 Feb, 2000, "Eyal Traitel" eyal.traitel@motorola.com wrote:
...
Are there any plans / ideas from Veritas on improving backup/restore times of
filers ?
Here's hoping.
...
It seems that the tape/backup s/w is not keeping up well with the filers' huge
sizes ?
Oh the number of times I've bewailed this too.
...
What is the best configuration that can give us best performance ?
Anyone fancy a quick poll on how fast they can backup how much?
...
-- End of excerpt from "Eyal Traitel"
-- 
-Mark                     ... an Englishman in London ...

Re: Backing up a filer