hi,
i am testing ndmp backup solutions on my f760[part of a cluster] running 5.36r2, against a spectralogic treefrog. questions:
1. once backup started sysstat 1 showed cpu util at about 40% during mapping and initially 100% during dump for about 2-3 minutes and then much lower numbers since then. is the 100% util normal? nothing else is running, system is not prod yet.
2. can ait2 tapes be "bad" fresh out of the wrapper? the software would not handle 1 of the tapes, backup vendor said tape was probably bad. what is the ndmp response to a "bad" tape?
3. is the chip in the ait tapes used by ndmp backup?
thanks
neil lehrer wrote:
hi,
i am testing ndmp backup solutions on my f760[part of a cluster] running 5.36r2, against a spectralogic treefrog. questions:
- once backup started sysstat 1 showed cpu util at about 40% during mapping and
initially 100% during dump for about 2-3 minutes and then much lower numbers since then. is the 100% util normal? nothing else is running, system is not prod yet.
The first stage in an NDMP backup is a snapshot creation of the directory/tree/path that you are backing up. This is very CPU intensive and it is not uncommon for a single snapshot creation to consume all the available CPU resources. NetApp recommends that you have a maximum of four NDMP sessions running on a filer at one time (on a F760, only 2 on a 740 or 720). Even with all four NDMP sessions running at the same time, our users rarely notice, even though the CPU is pegged. This may be different in your environment as we are using purely NFS, no CIFS of HTTP, on our filers; these other protocols may be more CPU intensive and may respond differently to something else hogging the CPU.
- can ait2 tapes be "bad" fresh out of the wrapper? the software would not
handle 1 of the tapes, backup vendor said tape was probably bad. what is the ndmp response to a "bad" tape?
I do not have much experience with AIT-2 tapes, but I can imagine that it is possible for a tape to be bad straight out of the box. As far as how NDMP handles a bad tape, in my experience it reports an error code which is interpreted by the backup software.
- is the chip in the ait tapes used by ndmp backup?
Again, limited experience with AIT tapes, but I can't imagine that NDMP is elegant enough to make use the MIC. Of course, with the latest implementation of NDMP in ONTAP 6.x, NetApp has (re)introduced support for Direct Access Recovery (DAR), which serves a similar purpose as the MIC in the AIT tapes. DAR writes periodic updates about which file it is writing, and can from this information, move the tape directly to the approximate location of the file you are restoring. Unfortunately, DAR does have some limitations, chiefly that it is constained to restoring files (not directories), and it is limited to roughly 1000 files at a time. But for restoring single files, it can't be beaten.
Geoff Hardin Dallas Semiconductor MIS UNIX geoff.hardin@dalsemi.com
hi,
i am testing ndmp backup solutions on my f760[part of a cluster] running 5.36r2, against a spectralogic treefrog. questions:
- once backup started sysstat 1 showed cpu util at about 40% during mapping and
initially 100% during dump for about 2-3 minutes and then much lower numbers since then. is the 100% util normal? nothing else is running, system is not prod yet.
I can answer this question.
At the beginning of any BSD format dump, there are a couple of bitmaps. One bitmap has a bit for every active inode in the subtree, at the time of the snapshot you're dumping. The other bitmap has a bit set for every inode on the dump tape.
On a level 0 dump, these bitmaps are the same. On an incremental dump, they are probably different (if a file hasn't changed, it is still active, but it won't be on the level 1 dump tape).
Anyway, the mapping phase builds up these maps. Then, at the beginning of the dumping phase, we slam the maps onto the tape.
Since your system in inactive, the entirety of the maps are probably in buffer cache. So we're just reading from memory and writing to tape.
Once that is done, we start reading the directory data from the file system. That is not all in buffer cache, so CPU usage drops some, and disk activity should jump.
On an active system, the bitmaps will probably not all be in cache. Furthermore, dump effectively "nices" its CPU consumption. It won't hog the CPU if NFS/CIFS etc. operations are in the queue. You may still see CPU hit 100% for 2 minutes at that stage in the future, but that's just dump using whatever CPU that the rest of the system has left over (why waste it? :)
Good luck, Stephen Manley DAM and NDMP Steve Nash Hairstyle Fan
- can ait2 tapes be "bad" fresh out of the wrapper? the software would not
handle 1 of the tapes, backup vendor said tape was probably bad. what is the ndmp response to a "bad" tape?
- is the chip in the ait tapes used by ndmp backup?
thanks
-
Geoff Hardin -
neil lehrer -
Stephen Manley