How do I find the block size of my database files on Linux?

First, find the block size of your filesystem. On Linux, the default block size for an ext3 filesystem will be 4096 bytes (4 KB):

[root@firestorm ~]# tune2fs -l /dev/datavg/eclipse
tune2fs 1.39 (29-May-2006)
Filesystem volume name:   /u2/eclipse
Last mounted on:          
Filesystem UUID:          996f19ea-80da-477d-b961-2873ebe8181b
Filesystem magic number:  0xEF53
Filesystem revision #:    1 (dynamic)
Filesystem features:      has_journal ext_attr resize_inode dir_index filetype sparse_super large_file
Default mount options:    (none)
Filesystem state:         clean
Errors behavior:          Continue
Filesystem OS type:       Linux
Inode count:              1310720
Block count:              5242880
Reserved block count:     262144
Free blocks:              2651137
Free inodes:              1125318
First block:              0
Block size: 4096 
Fragment size:            4096
Reserved GDT blocks:      1022
Blocks per group:         32768
Fragments per group:      32768
Inodes per group:         8192
Inode blocks per group:   512
Filesystem created:       Fri Sep 23 22:04:10 2011
Last mount time:          Mon Jan  9 13:03:16 2012
Last write time:          Tue Jan 17 13:41:40 2012
Mount count:              8
Maximum mount count:      20
Last checked:             Fri Sep 23 22:04:10 2011
Check interval:           15552000 (6 months)
Next check after:         Wed Mar 21 22:04:10 2012
Reserved blocks uid:      0 (user root)
Reserved blocks gid:      0 (group root)
First inode:              11
Inode size:		  256
Journal inode:            8
Default directory hash:   half_md4
Directory Hash Seed:      e4114643-fdd7-446d-ae9c-4bdea1063657
Journal backup:           inode blocks

Each UniVerse database file has its own setting for block size, which can be found by running the ANALYZE.FILE command from TCL, as in the example below:

>ANALYZE.FILE PRODUCT
File name                               = PRODUCT
File type                               = 18
File style and revision                 = 64BIT Revision 12
Number of groups in file (modulo)       = 30427
Separation = 4 
Number of records                       = 155092
Number of physical bytes                = 70756352
Number of data bytes                    = 52605264

Average number of records per group     = 5.0972
Average number of bytes per group       = 1728.9008
Minimum number of records in a group    = 2
Maximum number of records in a group    = 7

Average number of bytes per record      = 339.1875
Minimum number of bytes in a record     = 176
Maximum number of bytes in a record     = 2424

Average number of fields per record     = 110.3191
Minimum number of fields per record     = 108
Maximum number of fields per record     = 194

Groups   25%     50%     75%    100%    125%    150%    175%    200%  full

Multiply the separation by the filesystem block size for the database file block size. In this example, 4096 bytes * 4 = 16484 bytes (16 K).