More yummy stats.

| 3 Comments
The following numbers are from the Student side of our cluster. These are the NSS filesystem stats, colors are mine.
*****  Buffer Cache Statistics *****
Min cache buffers: 512
Num hash buckets: 262144
Min OS free cache buffers: 256
Num cache pages allocated: 140470
Cache hit percentage: 95%
Cache hit: 45220557
Cache miss: 2235514
Cache hit percentage(user): 93%
Cache hit(user): 30771799
Cache miss(user): 2160008
Cache hit percentage(sys): 99%
Cache hit(sys): 14448758
Cache miss(sys): 75506
Percent of buckets used: 39%
Max entries in a bucket: 8
Total entries: 138424
The line that worries me is the "cache hit percentage" sitting at 95%. The student side has a bit over 1TB on it, and these stats were captured during 'real usage' times when no backups were being run and real users were accessing things. So I have high confidence these are real. So we need to throw some more memory into these servers.

What kind of side-effects does this present as? Since not as much data is being cached as we need, this means that the server is going to disk more often than it otherwise should. This will present as slower file accesses. Not beastly slow, since this is FC-backed not SCSI-backed, but slower than it could be.

3 Comments

Quick question, and this maybe a stupid question but how did you output the Buffer Statistics?I have been tracking these myself and have not found a "easy" way to routinely capture the output. My attempts at redirecting the console output of nss /CacheStats >nsscache.txt has resulted in an error. It seems to think ">nsscache.txt" is part the the nss commandline. I am relatively unacustomed to NetWare, my background is more Unix where I have taken console redirection for granted. Thanks.

Novell is very tricky on this one. There isn't a way to redirect it from console. But there is another way to access that data. On the "_admin" volume on that server you can access that data from a file!\\server\_admin\Manage_NSS\GeneralStats.xmlcat that file and you get XML-ized output for the CacheStats command. This _admin directory works sort of (but not quite) like the /proc directory in unix-land. This is called the Virtual File Services. Lots of handy stuff in there if you care to dig.

Fantastic! That is even better than a basic text dump. It's already wrapped up in XML goodness. Thanks.