Penguin

Acronym for Self Monitoring, Analysis and Reporting Technology.

A standard for monitoring the health of IDE disks, particularly to alert the user before a disk crashes, but also offering a wealth of information about the HardDisk in general. If you see your BIOS refer to S.M.A.R.T., this is it.

For experimentation, grab the smartmontools (Debian, RedHat, Mandrake etc probably have it packaged) and have a look. First enable SMART
smartctl -e /dev/hdx
And then view its information
smartctl -a /dev/hdx

("a" = all information. "v" = vendor-specific)

Eg
  1. smartctl -v /dev/hda

Vendor Specific SMART Attributes with Thresholds: Revision Number: 16 Attribute Flag Value Worst Threshold Raw Value ( 1)Raw Read Error Rate 0x000f 074 069 025 122340577 ( 3)Spin Up Time 0x0003 098 098 000 0 ( 4)Start Stop Count 0x0032 100 100 020 7 ( 5)Reallocated Sector Ct 0x0033 100 100 036 0 ( 7)Seek Error Rate 0x000f 072 060 030 19550706 ( 9)Power On Hours 0x0032 100 100 000 767 ( 10)Spin Retry Count 0x0013 100 100 097 0 ( 12)Power Cycle Count 0x0032 100 100 020 238 (194)Temperature 0x0022 043 050 000 43 (195)Hardware ECC Recovered 0x001a 100 253 000 0 (197)Current Pending Sector 0x0012 100 100 000 0 (198)Offline Uncorrectable 0x0010 100 100 000 0 (199)UDMA CRC Error Count 0x003e 200 181 000 23 (200)Unknown Attribute 0x0000 100 253 000 0 (202)Unknown Attribute 0x0032 100 253 000 0

It's amazing, it gives you the total running time of the drive, how many times it's been power cycled (!), how many sectors have been remapped (and when!). Definitely one of computings li'l secrets.