Hi,
Thanks to the quick reply. I've read your blog on the Networker
multiplexing before posting the questions.
As far as I know, the adv_file backups are not multiplexed, although I
can't really say whether there is one-to-one mapping between a saveset and
an adv_file file on the host file system (probably not).
In this case I prefer the steady streaming from disk to tape than the
faster restore from a clone tape (cause the restore in this case would be
faster than the one from cloned multiplexed tape)
I believe EMC should give the customers the option to choose whether to
multiplex or not savesets when cloning/staging from adv_file device to
tape...or at least document what is possible and what is not. Hopefully
they have someone who is reading this list.
> BUT, now that I think about it, your issue is that NetWorker backups sent
> to a adv disk target aren't actually multiplexed. They look like they
> are, but each backup is actually stored in a separate file. Therefore,
> even if you follow the suggestions in my blog entry, you probably won't be
> multiplexing clones.
>
> In my testing of other devices and other backup products, I have been able
> to stream LTO-4 tape drives with a single stream of data from disk to tape
> during clone/copy operations. It's kind of the point, which I think is
> what you're saying. Since we went to disk to be able to make it easier to
> stream our tape drives, we didn't accomplish much if we're not streaming
> the tape when we're copying from disk to tape.
>
>
> Curtis Preston | VP Data Protection
> GlassHouse Technologies, Inc.
>
> T: +1 760 710 2004 | C: +1 760 419 5838 | F: F: +1 760 710 2009
> cpreston AT glasshouse DOT com | www.glasshouse.com
> Infrastructure :: Optimized
>
> -----Original Message-----
> From: EMC NetWorker discussion [mailto:NETWORKER AT LISTSERV.TEMPLE DOT EDU]
> On
> Behalf Of Mitko Stoyanov
> Sent: Wednesday, August 06, 2008 10:11 PM
> To: NETWORKER AT LISTSERV.TEMPLE DOT EDU
> Subject: [Networker] Networker D2D2T backups and D2T cloning speed
>
> Hi,
>
> I'm in a process of evaluating a D2D2T backup architecture which uses
> LTO4 as tape technology, and adv_file devices for the D2D part. The
> outcomes are to get faster recovery (via the D2D part), and speed up the
> backup of many slow smaller clients via backing first to disk, then
> cloning to tape (the current network infrastructure can't drive LTO4
> drives fast enough).
>
> Everything is going up to the expectations so far, except the
> cloning....from my research so far it looks like the D2T cloning is done
> as single-threaded job, with one saveset cloning at a time.
>
> That would be OK with large savesets (some are > 100GB) , but an
> incremental backup of a small Unix OS file system may produce a saveset
> only a few Kbytes. Such small savesets can't produce the steady data
> stream required for the LTO4 devices (shining their shoes...).
>
> Hopefully somebody here could answer some of these questions:
>
> * When Networker clones from adv_file device to tape, is the adv_file
> saveset copied as it is without looking inside what is saved, or is
> "restored" internally and then backed up as a saveset to the clone tape?
>
>
> * Is there any workaround for the single-threaded saveset cloning? Any
> plans to multiplex the adv_file savesets when cloning to tape? That
> looks to me as a major showstopper when using faster tape technologies
> to clone D2D backups, as eventually these backups have to go offsite,
> and the vast majority of clients use tapes for that..
>
> Regards,
>
> --ms
>
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>
>
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