NetWare 6.5 sp6 with all NSS volumes created and suddenly got the following

Volume VOL1 user data write (20204(zio.c(2282))) to block 7227050 (file
block 0)(ZID 56) failed

Tried nss /poolverify and got no errors, no warnings. Do I need to run nss
/poolrebuild and if so, do I have to backup the data before the action?