NDMP Backups or Better

mrtubz's picture

Hi All

We have recently implemented a BlueARC NAS device with 60TB of storage and have a Dual LTO 5 tape library. The BlueARC supports NDMP backup and from a post on your knowledge base you are not looking to implement NDMP in your software in the future. My question really is what would be the best way to get the full potential from the LTO drives when using Presstore?

I currently have a Trunked 4Gb link to our switch and 10GB to our NAS device, the Tape Library is connected over 4Gb Fibre, but I very rarely get above 5% buffer on the tape device, so the drives are obviously not being fed quickly enough. I have a client with the same setup but Atempo Time Navigator running NDMP and they get a significantly higher throughput to their drives.


ogminlo's picture

When not using NDMP, all the data has to go through the backup app's host (in your case your PresSTORE box). The way to up your throughput in that case is to make your host's links faster. How are you connected to the LTO drives? Can you install a 10Gb link between your BlueARC and your PresSTORE host? Is there room for more RAM in your PresSTORE host?

mrtubz's picture


Thanks for your reply, Ive not got a 10GB card in there, yet. That was probably going to be my next option really, although I didnt want to be putting in a £800 card and only see a minor increase in throughput.

In regards memory ive go it specced up to 20Gb of RAM in that box so im hoping that should be enough. ;-)

I have done some testing with a 10GB card and 8GB fibre card in a PC with 8GB of RAM running Windows XP and I probably doubled my throughput across 2 drive to around 100-150mb/s up from around 60-80mb/s I just wanted to see if anyone using presstore was getting nearer the 100Mb/s per drive that LTO 5 is capable of. Although im sure that depends on file size and number of files being pulled.


ogminlo's picture

The nature of the payload will have an impact on performance, since that 140 MBps max data rate for LTO-5 is only going to get close when streaming large files. That aside, to be able to support that kind of throughput on two drives, 4 aggregated GbE links [i]should/i be enough. What kind of throughput can you get across from the BlueARC if you just try a test like netperf? If it is better than 3Gbps it isn't the network slowing you down. Are your data payloads similar to those of your Atempo customer?

AWSven's picture

Often the file system access is a limiting factor regarding the speed.
PresSTORE works file based. So even on systems with high throughput, disk latency appears when repositioning the disk head to the next file. Thus reading many small files reduces significantly the speed compared to big files with the same amount of data in total.
A trick to overcome that is to start parallel jobs, e.g. by defining multiple backup plans that run concurrently and write to the same tape.
Namely big NAD or RAID systems are often optimizes for parallel access and allow to speedup the throughput that way.