I'm using a SSD for about 460GB of data on an Ubuntu 12.04 server. (The drive holds 560GB, so it is about 88% full.) I have had a program which does a lot of random access to the data (no writing), which I last ran (normally) a few days ago. When I ran it yesterday, it was suddenly significantly slower than before. The program just does random access to the drive.
Previously I could do about 5000 random lookups per second; now I'm only getting about 100. This is slower than doing random access to a HDD. (I benchmarked a few problems last year.)
The only thing I've done recently was to install gcc 4.7 and to upgrade all my packages. But, I tried compiling everything with clang and didn't see a difference.
The drive is formatted as
ext4 with the only options being
errors=remount-ro. I tried rebooting the machine and trimming the device but it didn't change things. Profiling the code shows it is spending all its time in
mmap calls. (Note that I'm not calling mmap directly -- I'm using all
Any idea what could cause this? I could re-format the drive if there was a chance it would help.
Edit: here is some benchmark data on a 2TB HDD and the 500GB SSD
sudo hdparm -Tt /dev/sdb1 /dev/sdb1: Timing cached reads: 6814 MB in 2.00 seconds = 3410.05 MB/sec Timing buffered disk reads: 458 MB in 3.00 seconds = 152.45 MB/sec sudo hdparm -Tt /dev/sdc1 /dev/sdc1: Timing cached reads: 6890 MB in 2.00 seconds = 3447.93 MB/sec Timing buffered disk reads: 780 MB in 3.01 seconds = 259.36 MB/sec
Here is the output from
=== START OF INFORMATION SECTION === Model Family: Intel 320 Series SSDs Device Model: INTEL SSDSA2CW600G3 Serial Number: CVPR140004B7600FGN LU WWN Device Id: 5 001517 9596df196 Firmware Version: 4PC10362 User Capacity: 600,127,266,816 bytes [600 GB] Sector Size: 512 bytes logical/physical Device is: In smartctl database [for details use: -P show] ATA Version is: 8 ATA Standard is: ATA-8-ACS revision 4 Local Time is: Sun Jan 26 16:46:53 2014 MST 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: (0x00) Offline data collection activity was never started. Auto Offline Data Collection: Disabled. 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: ( 1) seconds. Offline data collection capabilities: (0x75) SMART execute Offline immediate. No Auto Offline data collection support. Abort Offline collection upon new command. No Offline surface scan supported. Self-test supported. 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: ( 1) minutes. Conveyance self-test routine recommended polling time: ( 1) minutes. SCT capabilities: (0x003d) SCT Status supported. SCT Error Recovery Control supported. SCT Feature Control supported. SCT Data Table supported. SMART Attributes Data Structure revision number: 5 Vendor Specific SMART Attributes with Thresholds: ID# ATTRIBUTE_NAME FLAG VALUE WORST THRESH TYPE UPDATED WHEN_FAILED RAW_VALUE 3 Spin_Up_Time 0x0020 100 100 000 Old_age Offline - 0 4 Start_Stop_Count 0x0030 100 100 000 Old_age Offline - 0 5 Reallocated_Sector_Ct 0x0032 100 100 000 Old_age Always - 0 9 Power_On_Hours 0x0032 100 100 000 Old_age Always - 17833 12 Power_Cycle_Count 0x0032 100 100 000 Old_age Always - 13 170 Reserve_Block_Count 0x0033 100 100 010 Pre-fail Always - 0 171 Program_Fail_Count 0x0032 100 100 000 Old_age Always - 0 172 Erase_Fail_Count 0x0032 100 100 000 Old_age Always - 0 183 Runtime_Bad_Block 0x0030 100 100 000 Old_age Offline - 0 184 End-to-End_Error 0x0032 100 100 090 Old_age Always - 0 187 Reported_Uncorrect 0x0032 100 100 000 Old_age Always - 0 192 Unsafe_Shutdown_Count 0x0032 100 100 000 Old_age Always - 5 199 UDMA_CRC_Error_Count 0x0030 100 100 000 Old_age Offline - 0 225 Host_Writes_32MiB 0x0032 100 100 000 Old_age Always - 3236658 226 Workld_Media_Wear_Indic 0x0032 100 100 000 Old_age Always - 4973 227 Workld_Host_Reads_Perc 0x0032 100 100 000 Old_age Always - 65 228 Workload_Minutes 0x0032 100 100 000 Old_age Always - 1067143 232 Available_Reservd_Space 0x0033 100 100 010 Pre-fail Always - 0 233 Media_Wearout_Indicator 0x0032 096 096 000 Old_age Always - 0 241 Host_Writes_32MiB 0x0032 100 100 000 Old_age Always - 3236658 242 Host_Reads_32MiB 0x0032 100 100 000 Old_age Always - 6437718 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] Note: selective self-test log revision number (0) not 1 implies that no selective self-test has ever been run SMART Selective self-test log data structure revision number 0 Note: revision number not 1 implies that no selective self-test has ever been run 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.
[Edit: I'm continuing to work on this in the background. When I do resolve it, I will post something here.]