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Tips on Cache Volume for BorderManager

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By Craig Johnson

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Posted: 3 Nov 2005
 

A reader recently asked:

"I have noticed some speed issues with our BorderManager, and I think it is related to cache volume size and relative usage. At any given time, I can have 200 client active connections and 150 active server connections. We have around 14 Citrix Servers that serve 150 winterms. We also have around 250 workstations. Each of these devices can have 4-5 different web-based applications running and java connections as well. We have a 15MB Ethernet pipe to the Internet. What size cache volume would be recommended?

I have noticed that a load proxy -cc to clear the cache will allow the server to run decently for a few days, but then the server seems to slow down. It starts taking 5-10 seconds to display web pages between clicks (normally only 1-5 seconds). Remote Manager shows "available directory entries" at RED. I sometimes only have 5% left on the cache volume.

Any suggestions?"

And here's the response from Craig Johnson ...


Check your current activity screen, and based on current stats there, figure out what one week's worth of browsing content is. That is the approximate size you want for your cache volume capacity. I'm going to guess you need somewhere around 20-30GB.

If you want the absolute best read/write performance for cache, then do this:

Set up one cache volume per physical drive. These volumes must be 8 or 16k block size, no compression, no suballocation, TFS, and not mirrored or RAIDed. I would make them 20GB each, BUT it may help slightly to have 2 10GB or 4 5GB cache volumes on each drive. (I've not noticed a major performance difference with multiple cache volumes per drive, but it may come into play with big cache volumes that are very heavily used). Once the cache volumes are created, use VREPAIR to remote long namespace - it won't really help performance much, but it conserves a bit of RAM and doesn't hurt.

The above comes into play only if you have a read/write bottleneck in storing data to the cache volumes. It is always best to have each cache volume on different physical drives, but in 99% of the cases, it doesn't really matter if you are using one or multiple cache volumes on 1 drive, a RAID5 array, or mirrored drive, simply because read/write I/O is generally fast enough to keep up with the demand for most situations.

Remember that initially data is cached into RAM, and is only written to disk much later, so it is highly buffered for short-term disk I/O demands. You will see the need to optimize disk I/O for caching if you consistently are hitting the hot node limit (default=7000, I always tune servers to go up to 50,000, occasionally higher).

You could also change the cache volume sizes. Watch the server for a while to determine how much data is typically cached in 7 days. Try to get your cache volume capacity to be close to that. It is a good idea to have all cache volumes the same size.


For more BorderManager tips and how-to's, see Craig Johnsons web site at:
http://www.craigjconsulting.com


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