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NAS 2000s - Large data transfers use all available RAM

 
CA1217505
New Member

NAS 2000s - Large data transfers use all available RAM

We are trying to migrate from a NAS 1000 server to a NAS 2000. Using either Double-Take (Storage Mirroring) or just xcopy, we are having memory issues when transferring large amounts of data.

It seems that after a certain throughput rate has been reached (about 5% of a 1Gbps link); the available memory (RAM) in the system starts to plummet. We have 1GB of RAM in the system, with a 3GB static page file and the stock 64MB RAM in the external RAID controller.

The low available memory is shown clearly in task manager and perfmon, although it is not associated with any particular process. I.e., no process in task manager is showing large amounts of RAM used.

I do not have prior experience with large amounts of RAM not being accounted for in task manager, but I have a theory. Is it possible that the driver for the external RAID card is using this RAM as a queue for when it can't write out to disk fast enough?

I came to this theory when we noticed that if we stop the Storage Mirroring service (or xcopy, as we tried later), the RAM will slowly return in 10-20MB chunks. Over the course of a couple minutes, the RAM is released.

We also have anecdotal evidence of files being "written" to the NAS device, but not showing up for several seconds.

The nature of our file system is many small files. I.e. tens of millions of 20k files. We have a 1.3TB external storage array.

Any ideas?
1 REPLY 1
CA1217505
New Member

Re: NAS 2000s - Large data transfers use all available RAM

I should probably also note that these machines were re-installed with an image CD from HP. No non-HP software was installed. They are running Windows 2003 Server.