Just a note:

NDMP is a backup control protocol. It does not define a data format. We run into a lot of confusion on that point. Since NDMP is a standard, you might think that an NDMP backup on one storage array could be restored via NDMP on a different array. That's not a valid conclusion. It's not impossible that you can do that, but it depends on the tape format.

When NDMP first came out, it used the "dump" format. It was similar to ufsdump, and you could even restore the data on a Solaris box pretty easily, although you'd lose all the permission data. That's probably still doable to some degree, but it's not supported.

The problem with dump is it's a logical backup. ONTAP has to walk the directory tree, and the more files you have, the longer it takes. That's why there's a second format option - NDMP with SMtape format. It's documented under "Understanding SMTape engine for FlexVol volumes" in the ONTAP documentation.

I've never met anyone using it personally, but it's been around for a while. I think TSM was the first to support it. It basically does a snapmirror operation to a tape drive, which means you preserve the efficiency. Since it's not walking the files, it was far faster than NDMP with the dump format.

I'm pretty sure that you still can't do a single file restore with SMtape format. You'd have to restore the whole thing. That may or may not be sufficient. If a customer just wants an offsite copy of everything as a quarterly archive or protection against disaster, that should be a good option.

I don't work with tape backups any longer, so I don't know anyone personally who's used SMtape, but if someone on Toasters has used it please let us know how it worked out.


-----Original Message-----
From: toasters-bounces@teaparty.net [mailto:toasters-bounces@teaparty.net] On Behalf Of John Stoffel
Sent: Tuesday, May 16, 2017 3:15 AM
To: Jeffrey Mohler <jmohler@yahoo-inc.com>
Cc: toasters@teaparty.net
Subject: Re: NDMP Performance...


Jeffrey> Does anyone that is using NDMP for file-dense restores also
Jeffrey> notice a HUGE gap in time between starting the restore, and
Jeffrey> data to begin moving...with no observable load/activity during
Jeffrey> that odd bizzare Phase-0 period?

I'm not too surprised actually... the NDMP is really just a wrapper around the dump/restore built into OnTap, though I admit that maybe this has changed with cDOT.

In older 7-mode, it was just a single file under /root/<vol>/ that held the index of file(s) dumped to tape at which level.  So I doubt it's been improved all that much since.

Jeffrey> We can see -hours- of 0% CPU, 0KB to disk (short of CP label
Jeffrey> updates to them), which challenges us in other ways because it
Jeffrey> brings average dataset recover speed/times to low double-digit
Jeffrey> MB/sec numbers no matter how fast tape is.

_______________________________________________
Toasters mailing list
Toasters@teaparty.net
http://www.teaparty.net/mailman/listinfo/toasters