/netbsd: wd0a: error reading fsbn?

[scole_mail <scole_mail%gmx.com@localhost>]

While copying some files between disks I got these errors:

/netbsd: wd0a: error reading fsbn 3522624 of 3522624-3522751 (wd0 bn 3522687; cn 3494 tn 11 sn 42), retrying
/netbsd: wd0: (uncorrectable data error)
/netbsd: wd0a: error reading fsbn 3522624 of 3522624-3522751 (wd0 bn 3522687; cn 3494 tn 11 sn 42), retrying
/netbsd: wd0: (uncorrectable data error)
/netbsd: wd0: soft error (corrected)

and I retried to copy same files

/netbsd: wd0a: error reading fsbn 3522624 of 3522624-3522751 (wd0 bn 3522687; cn 3494 tn 11 sn 42), retrying
/netbsd: wd0: (uncorrectable data error)
/netbsd: wd0a: error reading fsbn 3522624 of 3522624-3522751 (wd0 bn 3522687; cn 3494 tn 11 sn 42), retrying
/netbsd: wd0: (uncorrectable data error)
/netbsd: wd0a: error reading fsbn 3522624 of 3522624-3522751 (wd0 bn 3522687; cn 3494 tn 11 sn 42), retrying
/netbsd: wd0: (uncorrectable data error)
/netbsd: wd0a: error reading fsbn 3522624 of 3522624-3522751 (wd0 bn 3522687; cn 3494 tn 11 sn 42), retrying
/netbsd: wd0: (uncorrectable data error)
/netbsd: wd0a: error reading fsbn 3522624 of 3522624-3522751 (wd0 bn 3522687; cn 3494 tn 11 sn 42), retrying
/netbsd: wd0: (uncorrectable data error)
/netbsd: wd0a: error reading fsbn 3522624 of 3522624-3522751 (wd0 bn 3522687; cn 3494 tn 11 sn 42)
/netbsd: wd0: (uncorrectable data error)

What does it mean and what corrective action should I take if
any?  Is the disk going bad or file(s) corrupted or what?  I 
was copying some large .tgz as well as normal directories of files.

Thanks