File Descriptor Configuration for MongoDB Deployment

Hi,

I read the link on mongo db site regarding "Too many open files". (http://www.mongodb.org/display/DOCS/Too+Many+Open+Files)
My MongoDB Setup is:
1. 1 MongoS, 3 MongoC, 10 MongoD
2. All MongoDs are running on one server.
3. On MongoD I am using "--smallfiles" which creates files of maximum 512 MB on disk.
4. Total disk for all 10 shards is 15TB i.e. 1.5 TB per shard.
5. At a time total 365 databases are present in the system.

According to mongodb the formula is:
//TotalSize = `du -gs <db-path> | cut -f 1`

1. = (TotalSizeGB/2) + (NumberOfDBs) + (max(maxConns, 20,000)) + 5%-overhead
   I calculated file descriptor value for my deployment using above formula. Calculation is:

1. = (15 * 1024)/2 + 365*10 + 20,000 + 5% = 32896

My purpose for asking this question is: I set file descriptor value as 35000 on my server.
But still I am getting "Too Many Open files" error. And this error is coming frequently. (One case which I have seen is when running show dbs command)
So Should file descriptor value in my deployment be:

Since filesize in my case is 512 MB instead of 2048 MB(Default) so multiplying TotalSizeGB by 4:

1. = (15 * 1024 * 4)/2 + 365*10 + 20,000 + 5% = 57088

T&R,
jitendra verma