Hi,
Running ATS 4.0.1 (and 4.0.2) I got the next errors in de diag.log: [Oct 31 07:35:26.150] Server {0x1} WARNING: unable to set file '/opt/ts/var/trafficserver/host.db' size to 25935872: 22, Invalid argument [Oct 31 07:35:26.150] Server {0x1} WARNING: header missing/corrupt: [hostdb.config] : reinitializing database [Oct 31 07:35:26.151] Server {0x1} NOTE: reconfiguring host database [Oct 31 07:35:26.151] Server {0x1} WARNING: unable to set file '/opt/ts/var/trafficserver/host.db' size to 25935872: 22, Invalid argument After searching in de code which lead to ink_file.cc where the posix_fallocate function is used. Omnios which is a distro of illumios is using zfs as default file system. Searching on the internet gives some hints about problems with the posix_fallocate function. So I changed the code in ink_file.cc a bit (line 344): #if HAVE_POSIX_FALLOCATE && !defined(solaris) return posix_fallocate(fd, 0, size); #else This resolves the issue (for now) but gives the next error: [Nov 1 21:27:47.134] Server {0x1} WARNING: bad hardware sector size 131072, resetting to 8192 Zfs is using a default recordsize of 128K so changing it to 8K resolves this issue to. Sjaak