"SMART Usage Attribute: 194 Temperature_Celsius changed from 146 to 150". This is on CentOS 6.6.
What does this really mean? Is the drive really hot or is this perhaps a software bug? The drive is an eSATA 2TB drive and it feels cool to the touch and the server located in a basement is 70F.
# smartctl -A /dev/sdb
smartctl 5.43 2012-06-30 r3573 [x86_64-linux-2.6.32-504.16.2.el6.x86_64] (local build)
Copyright (C) 2002-12 by Bruce Allen, http://smartmontools.sourceforge.net
=== START OF READ SMART DATA SECTION ===
SMART Attributes Data Structure revision number: 16
Vendor Specific SMART Attributes with Thresholds:
ID# ATTRIBUTE_NAME FLAG VALUE WORST THRESH TYPE UPDATED WHEN_FAILED RAW_VALUE
1 Raw_Read_Error_Rate 0x000b 100 100 016 Pre-fail Always - 0
2 Throughput_Performance 0x0005 134 134 054 Pre-fail Offline - 89
3 Spin_Up_Time 0x0007 123 123 024 Pre-fail Always - 507 (Average 505)
4 Start_Stop_Count 0x0012 100 100 000 Old_age Always - 89
5 Reallocated_Sector_Ct 0x0033 100 100 005 Pre-fail Always - 0
7 Seek_Error_Rate 0x000b 100 100 067 Pre-fail Always - 0
8 Seek_Time_Performance 0x0005 135 135 020 Pre-fail Offline - 26
9 Power_On_Hours 0x0012 096 096 000 Old_age Always - 29541
10 Spin_Retry_Count 0x0013 100 100 060 Pre-fail Always - 0
12 Power_Cycle_Count 0x0032 100 100 000 Old_age Always - 71
192 Power-Off_Retract_Count 0x0032 100 100 000 Old_age Always - 205
193 Load_Cycle_Count 0x0012 100 100 000 Old_age Always - 205
**194 Temperature_Celsius 0x0002 150 150 000 Old_age Always - 40 (Min/Max 20/49)**
196 Reallocated_Event_Count 0x0032 100 100 000 Old_age Always - 0
197 Current_Pending_Sector 0x0022 100 100 000 Old_age Always - 0
198 Offline_Uncorrectable 0x0008 100 100 000 Old_age Offline - 0
199 UDMA_CRC_Error_Count 0x000a 200 200 000 Old_age Always - 9
That is just SMART attribute value. It is not the temperature in any regular unit. (it is more like a number between 255 (really really cold) and 0 (really really hot), depending on drive what is hot and what not)
If you want to see the temp of your drive use
smartctl -A /dev/sdx
You'll get table like this:
RAW_VALUE
is what you're looking for ... (my drive is quite warm at 45°C)VALUE
is the attribute value and when it gets belowTHRESH
, the drive is getting ready to ask for replacement. (Not all attributes have threshold, just like my temperature)With regards to what is hot and what is not, it really depends on drive. There is a somewhat dated paper from Google on drive failure rates, which states that drives around 40°C have the lowest failure rates (at least for google and in 2007). I remember reading another paper (can't find it now) which stated, that high temperature is not a problem for hard drive. Sharp and frequent temperature changes can cause the disk to fail sooner. So as long as the drive temp is pretty stable (you can monitor that using something like munin), you should be fine.
smartd
is reporting any changes in attributes. It does not mean that there is something wrong.