Slow Flat File Backups

Hello Experts,

We have 2 solaris clients that we have flat file backups and these take almost 12-15 hours to get completed due to very small files on the clients.

So do you recommend if we take multistreaming backups of these clients this would take less time and help us we can not go for flash backup.

But what about the I/O procressing of the client if we enable 4-5 streams per servers on the policy.?

Is there any performance issue on client?  

Pls help thanks so very much.