> Message: 9 > Date: Tue, 03 Jul 2007 08:18:23 -0700 > From: Kenny <[EMAIL PROTECTED]> > Subject: [Veritas-bu] VTL with NDMP > To: VERITAS-BU@mailman.eng.auburn.edu > Message-ID: <[EMAIL PROTECTED]> > > > I am doing some research to see if a VTL will help my NDMP performance. > > Currently I backup my Net App environment over the LAN. I am looking to > improve backup and restore performance.
So you are running three-way NDMP right now? Or are you backing up over NFS? > I have a LTO-3 Tape library that can be fiber attached to the Net App filer. > My concern is that the Net App filer will not be able to stream to the tape > drives and I will kill my performance since the tape will have to do lots of > re-positioning and start and stop. > > I was thinking a VTL would be able to match the speed of the net app box > thus the performance would be optimized. LTO-3: 80 MB/s native, 160MB/s compressed. That's pretty fast. VTL: 100-180 MB/s. Make sure your VTL vendor is doing compression in hardware, otherwise turning on compression can reduce your speeds by 50%. We have a very large NDMP (EMC Celerra -> LTO-3) shop here, and I can tell you that very rarely does the backend disk have the horsepower to push LTO-3 much faster than 95 MB/s with real-world tests. With contrived data on a stand-alone Celerra we saw less than a 5% difference between LTO-3 and the VTLs that we were testing. YMMV, of course, but we didn't see a large enough performance advantage to move to VTL. Not only that, but if you are backing up data with long retention periods, be prepared to buy a whole lot of disk for your VTL, unless you will archive off to tape from your VTL. > Questions: > > I have newer and older Net App boxes, assuming a 2GB san, what performance > can I expect using NDMP? > Out of the box, untuned, 50-80 MB/s to LTO-3. Tuned, 70-160 MB/s. >From my experience, VTLs don't really need much tuning, as does tape. They are fast out of the box, but tape can be almost as fast (within 5%) when tuned properly. > Do you see an advantage using VTL in place of multiple LTO-3 drives? Depends on your data. If you are backing up mostly data that is already compressed, you will be limited to the native speed of LTO-3, which is 80 MB/s. A VTL will be faster in that case. However, if your data is mostly uncompressed, then tape is just as fast as VTL. Also, if you have 2 Gb/s coming out of your NetApp, and 2 Gb/s coming into your VTL, the most you are going to see is 240 MB/s. That's three LTO-3 drives. Sure, you can create 16 virtual drives on your VTL, but that's 500% oversubscribed on throughput. > > How many streams are possible (Using NBU 6.x)? Do the number of streams help > in a VTL environment? how about a tape environment? A NetApp filer supports 16 concurrent NDMP sessions at one time. They cannot be muxed, but you can certainly multi-stream to individual drives concurrently. > > Any recommendations on performance tuning with NBU 6 and NDMP? This is more of an issue with tape than VTL. With tape, SIZE_DATA_BUFFERS_NDMP is your friend. HTH. -- nick > > Thanks in advance! > > Paul Kenny > > +---------------------------------------------------------------------- > |This was sent by [EMAIL PROTECTED] via Backup Central. > |Forward SPAM to [EMAIL PROTECTED] > +---------------------------------------------------------------------- _______________________________________________ Veritas-bu maillist - Veritas-bu@mailman.eng.auburn.edu http://mailman.eng.auburn.edu/mailman/listinfo/veritas-bu