Insight can handle a 8TB(10 millions tracks) dataset fine without any performance degradation. The following information is taken from the Insight Guide:
Specifies whether to compress the records that are written to the history data sets. CA SYSVIEW for DB2 uses hardware compression to compress history records, which generate little CPU overhead. The option can be turned on and off without reallocating the ACCT and STAT files.
These files can have both uncompressed and compressed records mixed in the same file.