Slow file access
Tod Merley
todbot88 at gmail.com
Tue Dec 4 22:44:28 UTC 2007
On Dec 4, 2007 2:03 PM, Konstantin Svist <fry.kun at gmail.com> wrote:
> Here's the situation:
>
> I have some large mysql db files on my main partition. For some strange
> reason, some of these files are very slow to be read off the disk:
> ~3MB/s (I'm SCPing them to another machine). File size doesn't seem to
> be relevant (other files of approximately same size are being
> transferred at ~20MB/s), and the speed is not the same throughout the file.
>
> My first thought was that the file got very fragmented (I'm fairly sure
> that the partition was filled up to [almost] 100% at some point).
> Usually, that can be remedied by copying the file to another location on
> the same partition.. or rather, that's what would fix fragmented files
> on NTFS. When I tried that, the read speed of the new file was better by
> a small amount (up to ~5MB/s) - although that could be because the file
> was still in the memory cache.
>
> I also thought that HD might be nearing the end of its useful lifetime
> (and has to re-read the sectors, causing the horrible slowdown), but I
> didn't notice any alerts from SMART (including the output of smartctl
> -a, anyway)
>
> The partition is ~60-70% full, type ext3 with noatime enabled.
> Speed tests were performed by "scp myfile localhost:/dev/null"
>
>
>
>
> smartctl version 5.33 [i386-redhat-linux-gnu] Copyright (C) 2002-4 Bruce Allen
> Home page is http://smartmontools.sourceforge.net/
>
> === START OF INFORMATION SECTION ===
> Device Model: ST3300831A
> Serial Number: 3NF17FA8
> Firmware Version: 3.04
> User Capacity: 300,069,052,416 bytes
> Device is: Not in smartctl database [for details use: -P showall]
> ATA Version is: 7
> ATA Standard is: Exact ATA specification draft version not indicated
> Local Time is: Tue Dec 4 14:01:27 2007 PST
> SMART support is: Available - device has SMART capability.
> SMART support is: Enabled
>
> === START OF READ SMART DATA SECTION ===
> SMART overall-health self-assessment test result: PASSED
>
> General SMART Values:
> Offline data collection status: (0x82) Offline data collection activity
> was completed without error.
> Auto Offline Data Collection: Enabled.
> Self-test execution status: ( 0) The previous self-test routine completed
> without error or no self-test has ever
> been run.
> Total time to complete Offline
> data collection: ( 430) seconds.
> Offline data collection
> capabilities: (0x5b) SMART execute Offline immediate.
> Auto Offline data collection on/off support.
> Suspend Offline collection upon new
> command.
> Offline surface scan supported.
> Self-test supported.
> No Conveyance Self-test supported.
> Selective Self-test supported.
> SMART capabilities: (0x0003) Saves SMART data before entering
> power-saving mode.
> Supports SMART auto save timer.
> Error logging capability: (0x01) Error logging supported.
> General Purpose Logging supported.
> Short self-test routine
> recommended polling time: ( 1) minutes.
> Extended self-test routine
> recommended polling time: ( 101) minutes.
>
> 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 062 050 006 Pre-fail Always - 217294
> 3 Spin_Up_Time 0x0003 097 097 000 Pre-fail Always - 0
> 4 Start_Stop_Count 0x0032 100 100 020 Old_age Always - 25
> 5 Reallocated_Sector_Ct 0x0033 100 100 036 Pre-fail Always - 0
> 7 Seek_Error_Rate 0x000f 081 060 030 Pre-fail Always - 8837462413
> 9 Power_On_Hours 0x0032 084 084 000 Old_age Always - 14629
> 10 Spin_Retry_Count 0x0013 100 100 097 Pre-fail Always - 0
> 12 Power_Cycle_Count 0x0032 100 100 020 Old_age Always - 59
> 194 Temperature_Celsius 0x0022 047 064 000 Old_age Always - 47 (Lifetime Min/Max 0/22)
> 195 Hardware_ECC_Recovered 0x001a 062 049 000 Old_age Always - 217294
> 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
> 200 Multi_Zone_Error_Rate 0x0000 100 253 000 Old_age Offline - 0
> 202 TA_Increase_Count 0x0032 100 253 000 Old_age Always - 0
>
> SMART Error Log Version: 1
> No Errors Logged
>
> SMART Self-test log structure revision number 1
> No self-tests have been logged. [To run self-tests, use: smartctl -t]
>
>
> SMART Selective self-test log data structure revision number 1
> SPAN MIN_LBA MAX_LBA CURRENT_TEST_STATUS
> 1 0 0 Not_testing
> 2 0 0 Not_testing
> 3 0 0 Not_testing
> 4 0 0 Not_testing
> 5 0 0 Not_testing
> Selective self-test flags (0x0):
> After scanning selected spans, do NOT read-scan remainder of disk.
> If Selective self-test is pending on power-up, resume after 0 minute delay.
>
>
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Hi Konstantin Svist!
If I understand the data:
Lots of seek errors - lots of ECC recoveries - running very warm (117
degrees Farenheit). Check for cooling issues. Low level format if
possible.
Sounds kind of like the little guy has worked very hard for you the
last year and a half! Yes, maybe time to change him out.
Just some thoughts!
Tod
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