SCSI performance question

[Needitcooler]

We have a system at work that includes a media server with a 10,000 rpm Seagate SCSI drive. The server mainly streams media. We have been doing some testing and we are averaging around 19 MB/s. This seems really low to me. What kind of average speeds should I expect for this harddrive as a media server? Imagine that the system is not a bottleneck in any way.

http://www.storagereview.com/articles/200412/20041201ST3300007LW_1.html

Thanks for any help.

[Xaotic]

I will not be around long tonight, but some additional information will help. What controller are you using, specs of the server, where are you measuring the 19MB/s, what speed network is it attached to, and how are you measuring the 19MB/s?

From drive specs, I'd expect raw rates from 70-75MB/s at outer sectors down to around 40MB/s continuous, with defragged drives. However, systems and controller can have enormous effect on drive performance.

[dicecca112]

if I had to guess I'd say your controller is bottlenecking the system. Is the drive u320 or u160?

[Needitcooler]

U320.

I am not sure on the controller. I will check the specs tomorrow. The 19 MB/s was an estimate measured by determining the maximum clients that could pull MPEG1 video at 1.57 mbps before we started measuring dropped packets. That ended up being around 90 clients.

90 clients x 1.57 mbps = 141.3 mbps
141.3 mbps / 8 = 17.7 MB/s

[Needitcooler]

System specs:

Controller - http://www.lsilogic.com/products/scsi_ics/lsi53c1030.html

PowerPC750fx running at 733 MHz
256 MB ECC SDRAM running at 133 MHz

[Xaotic]

256 MB ECC SDRAM running at 133 MHz

This probably the source of the issues. The OS and IO streams are trying to coexist in 256MB of RAM. Since you are sending the data must be buffered to be transmitted on the network, it has to reside in RAM for a short time. Check for RAM utilization and page file usage in a monitoring program and see where you stand. I usually prefer 2GB of RAM for high bandwidth IO servers, but tend to overbuild. You should be able to get by with less depending on OS requirements, but a GB is usually a good starting point. As a quick check, adding another 256MB will allow you to evaluate for changes.

[Needitcooler]

We tried it out with 512 MB of ram today, but there was no improvement. I am beginning to think that the processor is the bottleneck.

[Xaotic]

That was the other option, but I'd rather start with the inexpensive stuff first. Have you tried any monitoring of resources and CPU utilization?

[Needitcooler]

We haven't gotten around to testing the media server yet. We are busy testing something else at the moment. Thanks for the help though Xaotic. As soon as I can run some tests on the media server I will post back.