Quote: "My NDMP tape backups from the R200 are pretty slow. I average about 2 MBytes per sec. Note that backups of other volumes on the R200 work really well, so there is no problem on the R200 or the network."
Your 2MB/sec sampling, when was that taken? Was it at the beginning, middle, end of the backup? You -should- be getting a really slow through-put rate at the start of a backup, since ndmp basically walks through and takes a look at each file before actually backing them up. When you have a large volume it will take a while to look at each file, it's worse with volumes that have a large number of small files.
We had an 8TB 560ish million file vol that would take forever. It seemed to just sit there practically idle, before it would take off and begin backing up. This was too impractical for such a long time for a single backup, so we changed up our future growth area, and now do a snapmirror each qtree to a single volume and then ndmp that out. It still takes time, but it allows us to get a clean backup of separate areas each within their own timeframe.
Anyway, my point being, are you seeing slow movement in just the beginning, are you competing backups, and have you captured peak performance? Also, would it be possible to change the way you store your data, or back up in sections? I know it's not fixing the issue, it's just working around it, but it could either help in the meantime while you look at minra, or possibly become a smoother process for you.
-- *------------------- Michael Callaway Server Administrator NTTA/IT 214-461-2033 -------------------- -----Original Message----- From: owner-toasters@mathworks.com [mailto:owner-toasters@mathworks.com] On Behalf Of Peter D. Gray Sent: Thursday, August 31, 2006 6:53 PM To: toasters@mathworks.com Subject: Re: when to use minra ?
Thanks for the replies. Some background on this question.
I have 2 filers used for email storage (NFS, attached to 2 mirapoint mail stores). They have lots of small files. I am mirroring these 2 filers to an R200 for backup, but I also take tape copies via NDMP every 30 days or so. The volumes contain about 350GB each of actual data, excluding snapshots, and 5 million files.
My NDMP tape backups from the R200 are pretty slow. I average about 2 MBytes per sec. Note that backups of other volumes on te R200 work really well, so there is no problem on the R200 or the network.
I saw the comment that turning off minra can have a big impact on backup performance so I thought I would try it. But discovered that the setting would have to be changed on the mirror source which is not so good (maybe).
It would be nice if that setting could be changed on the mirror target but not the source, but I can see why that not possible.
So, I wondered if I could justify setting minra on on the source volumes but would need some way to predict the impact.
It sounds like turing on minra is not usually a good idea, so I guess I am stuck with slow NDMP backups.
Just out of interest, does anybody understand why minra has an impact on backup speed. I assume the read ahead does not go past end of file but that is the only explanation I can think of as to why it would have an impact?
Regards, pdg
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