Estou usando um SSD para cerca de 460 GB de dados em um servidor Ubuntu 12.04. (A unidade tem 560 GB, então está com 88% da capacidade total.) Eu tive um programa que faz muito acesso aleatório aos dados (sem escrever), que eu executei (normalmente) pela última vez há alguns dias. Quando eu corri ontem, foi de repente significativamente mais lento do que antes. O programa apenas faz acesso aleatório à unidade.
Anteriormente, eu podia fazer cerca de 5000 pesquisas aleatórias por segundo; agora eu estou recebendo apenas cerca de 100. Isso é mais lento do que fazer acesso aleatório a um HDD. (Eu testei alguns problemas no ano passado.)
A única coisa que fiz recentemente foi instalar o gcc 4.7 e atualizar todos os meus pacotes. Mas eu tentei compilar tudo com clang e não vi diferença.
A unidade está formatada como ext4 , com as únicas opções sendo errors=remount-ro . Eu tentei reiniciar a máquina e aparar o dispositivo, mas isso não mudou as coisas. A criação de perfil do código mostra que ele está gastando todo o tempo em open , close e mmap chamadas. (Observe que não estou chamando o mmap diretamente - estou usando todas as chamadas C -style fopen fseek e fread .)
Alguma idéia do que poderia causar isso? Eu poderia reformatar a unidade se houvesse uma chance de ajudar.
Edit: aqui estão alguns dados de benchmark em um disco rígido de 2TB e o SSD de 500GB
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
Aqui está a saída de smartctl :
=== 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: estou continuando a trabalhar nisso em segundo plano. Quando eu resolvê-lo, vou postar algo aqui.]