Il 26-08-2017 22:58 sonofagun@xxxxxxxxxxxxxxx ha scritto:
Hello guys, this is a very interesting thread but I will join it
tomorrow!
I have read a similar discussion for SSDs some time ago. That took
place here [1]. Corruption of such devices can lead to complete data
loss and not just corruption.
I just read the thread at https://marc.info/?t=149186660400002&r=1&w=2,
it was very interesting. However, it seems to me that it ended without
a clear solution, right?
Anyway, the opacity of the FTL (flash translation layer) surely is a
significant cause of concern/danger. Unexpected power losses can wreak
havock on SSDs.
Please install smartmontools and post its output here for each disk so
that I can see if your disks are healthy. Also I must see their
firmware version as there might be a firmware update available.
Fortunately, the issue is solved now: I tracked back it to a faulty SATA
power cable. However, the SMART reports of both disk is very
interesting:
GOOD DISK (sda):
[root@nas ~]# smartctl -A /dev/sda
smartctl 6.2 2013-07-26 r3841 [x86_64-linux-3.10.0-514.el7.x86_64]
(local build)
Copyright (C) 2002-13, Bruce Allen, Christian Franke,
www.smartmontools.org
=== START OF READ SMART DATA SECTION ===
SMART Attributes Data Structure revision number: 10
Vendor Specific SMART Attributes with Thresholds:
ID# ATTRIBUTE_NAME FLAG VALUE WORST THRESH TYPE
UPDATED WHEN_FAILED RAW_VALUE
1 Raw_Read_Error_Rate 0x000f 111 099 006 Pre-fail Always
- 30483624
3 Spin_Up_Time 0x0003 093 091 000 Pre-fail Always
- 0
4 Start_Stop_Count 0x0032 100 100 020 Old_age Always
- 46
5 Reallocated_Sector_Ct 0x0033 100 100 010 Pre-fail Always
- 0
7 Seek_Error_Rate 0x000f 077 060 030 Pre-fail Always
- 55353954
9 Power_On_Hours 0x0032 091 091 000 Old_age Always
- 8535
10 Spin_Retry_Count 0x0013 100 100 097 Pre-fail Always
- 0
12 Power_Cycle_Count 0x0032 100 100 020 Old_age Always
- 44
184 End-to-End_Error 0x0032 100 100 099 Old_age Always
- 0
187 Reported_Uncorrect 0x0032 100 100 000 Old_age Always
- 0
188 Command_Timeout 0x0032 100 100 000 Old_age Always
- 0
189 High_Fly_Writes 0x003a 100 100 000 Old_age Always
- 0
190 Airflow_Temperature_Cel 0x0022 067 060 045 Old_age Always
- 33 (Min/Max 30/40)
191 G-Sense_Error_Rate 0x0032 100 100 000 Old_age Always
- 0
192 Power-Off_Retract_Count 0x0032 100 100 000 Old_age Always
- 24
193 Load_Cycle_Count 0x0032 100 100 000 Old_age Always
- 67
194 Temperature_Celsius 0x0022 033 040 000 Old_age Always
- 33 (0 14 0 0 0)
197 Current_Pending_Sector 0x0012 100 100 000 Old_age Always
- 0
198 Offline_Uncorrectable 0x0010 100 100 000 Old_age
Offline - 0
199 UDMA_CRC_Error_Count 0x003e 200 200 000 Old_age Always
- 0
Note the low (expected) Start_Stop_Count (46)
BAD DISK (sdb):
[root@nas ~]# smartctl -A /dev/sdb
smartctl 6.2 2013-07-26 r3841 [x86_64-linux-3.10.0-514.el7.x86_64]
(local build)
Copyright (C) 2002-13, Bruce Allen, Christian Franke,
www.smartmontools.org
=== START OF READ SMART DATA SECTION ===
SMART Attributes Data Structure revision number: 10
Vendor Specific SMART Attributes with Thresholds:
ID# ATTRIBUTE_NAME FLAG VALUE WORST THRESH TYPE
UPDATED WHEN_FAILED RAW_VALUE
1 Raw_Read_Error_Rate 0x000f 106 099 006 Pre-fail Always
- 11030016
3 Spin_Up_Time 0x0003 095 091 000 Pre-fail Always
- 0
4 Start_Stop_Count 0x0032 100 100 020 Old_age Always
- 661
5 Reallocated_Sector_Ct 0x0033 100 100 010 Pre-fail Always
- 0
7 Seek_Error_Rate 0x000f 078 060 030 Pre-fail Always
- 60912204
9 Power_On_Hours 0x0032 091 091 000 Old_age Always
- 8536
10 Spin_Retry_Count 0x0013 100 100 097 Pre-fail Always
- 0
12 Power_Cycle_Count 0x0032 100 100 020 Old_age Always
- 44
184 End-to-End_Error 0x0032 100 100 099 Old_age Always
- 0
187 Reported_Uncorrect 0x0032 100 100 000 Old_age Always
- 0
188 Command_Timeout 0x0032 100 100 000 Old_age Always
- 0
189 High_Fly_Writes 0x003a 100 100 000 Old_age Always
- 0
190 Airflow_Temperature_Cel 0x0022 067 061 045 Old_age Always
- 33 (Min/Max 29/39)
191 G-Sense_Error_Rate 0x0032 100 100 000 Old_age Always
- 0
192 Power-Off_Retract_Count 0x0032 100 100 000 Old_age Always
- 639
193 Load_Cycle_Count 0x0032 100 100 000 Old_age Always
- 672
194 Temperature_Celsius 0x0022 033 040 000 Old_age Always
- 33 (0 14 0 0 0)
197 Current_Pending_Sector 0x0012 100 100 000 Old_age Always
- 0
198 Offline_Uncorrectable 0x0010 100 100 000 Old_age
Offline - 0
199 UDMA_CRC_Error_Count 0x003e 200 200 000 Old_age Always
- 0
Note the *much* higher Start_Stop_Count (661); however, the
Power_Cycle_Count was the same (44).
So yes, while HDDs surely are more resilient than SSDs to unexpected
power losses, a micro-powerloss which corrupt/invalidate the disk's
cache content without giving the host a change to notice *will* cause
data corruption, sometime on acked syncronized writes also (I had a
filesystem journal corruption).
However, as stated in this thread, SATA does not really has a provision
to detect failed command due to micro-powerlosses nor to detect and
invalid/corrupted disk cache. So it seems the better "line of defese" is
to monitor (via SMART) the start/stop or power cycles count.
Regards.
--
Danti Gionatan
Supporto Tecnico
Assyoma S.r.l. - www.assyoma.it
email: g.danti@xxxxxxxxxx - info@xxxxxxxxxx
GPG public key ID: FF5F32A8
