slow read hd performance..

papierschiff · 2009-05-09 14:36:13

hej,
with hdparm -tT /dev/sda4 i get the ouput:

/dev/sda4:
Timing cached reads: 1686 MB in 2.00 seconds = 843.04 MB/sec
Timing buffered disk reads: 212 MB in 3.00 seconds = 70.66 MB/sec

this looks ok. but when i try it with real files (dd if=/home/hanna/temp/bigfile.txt of=/dev/null)
i geht only:

1419547960 Bytes (1,4 GB) kopiert, 69,6285 s, 20,4 MB/s

i have 2GB ram, if the file is smaller i get a much better read-speed. but why only 20MB/s? this looks soo slow.

lg
papierschiff

EVRAMP · 2009-05-09 14:52:35

To compare your results:

hdparm -tT /dev/sda

/dev/sda:
 Timing cached reads:   780 MB in  2.00 seconds = 389.84 MB/sec
 Timing buffered disk reads:  184 MB in  3.03 seconds =  60.79 MB/sec


dd if=/home/evramp/bigfile.txt of=/dev/null
(595 MB) copied, 15,1516 s, 39,2 MB/s

What HDD do you have? What filesystem are you using?
What shows you hdparm /dev/sda -I? Aim at the line saying Recommended acoustic management value: 254, current value: xxx and line above saying Advanced power management level: xxx => these can slow your drive a bit.

Last edited by EVRAMP (2009-05-09 14:53:20)

papierschiff · 2009-05-09 15:02:34

hej, thanks for your reply. its a seagate hd, 500GB, ext3

sudo hdparm -I /dev/sda                          

/dev/sda:

ATA device, with non-removable media
        Model Number:       ST3500620AS                             
        Serial Number:      9QM30RKX                                
        Firmware Revision:  LC11                                    
        Transport:          Serial                                  
Standards:                                                          
        Used: unknown (minor revision code 0x0029)                  
        Supported: 8 7 6 5                                          
        Likely used: 8                                              
Configuration:                                                      
        Logical         max     current                             
        cylinders       16383   16383                               
        heads           16      16                                  
        sectors/track   63      63                                  
        --                                                          
        CHS current addressable sectors:   16514064                 
        LBA    user addressable sectors:  268435455                 
        LBA48  user addressable sectors:  976773168                 
        Logical/Physical Sector size:           512 bytes           
        device size with M = 1024*1024:      476940 MBytes          
        device size with M = 1000*1000:      500107 MBytes (500 GB) 
        cache/buffer size  = 16384 KBytes                           
        Nominal Media Rotation Rate: 7200                           
Capabilities:                                                       
        LBA, IORDY(can be disabled)                                 
        Queue depth: 32                                             
        Standby timer values: spec'd by Standard, no device specific minimum
        R/W multiple sector transfer: Max = 16  Current = 1                 
        Recommended acoustic management value: 254, current value: 0        
        DMA: mdma0 mdma1 mdma2 udma0 udma1 udma2 udma3 udma4 udma5 *udma6   
             Cycle time: min=120ns recommended=120ns                        
        PIO: pio0 pio1 pio2 pio3 pio4                                       
             Cycle time: no flow control=120ns  IORDY flow control=120ns    
Commands/features:                                                          
        Enabled Supported:                                                  
           *    SMART feature set                                           
                Security Mode feature set                                   
           *    Power Management feature set                                
           *    Write cache                                                 
           *    Look-ahead                                                  
           *    Host Protected Area feature set                             
           *    WRITE_BUFFER command                                        
           *    READ_BUFFER command                                         
           *    DOWNLOAD_MICROCODE                                          
                SET_MAX security extension                                  
           *    48-bit Address feature set                                  
           *    Device Configuration Overlay feature set                    
           *    Mandatory FLUSH_CACHE                                       
           *    FLUSH_CACHE_EXT                                             
           *    SMART error logging                                         
           *    SMART self-test                                             
           *    General Purpose Logging feature set                         
           *    64-bit World wide name                                      
           *    Write-Read-Verify feature set                               
           *    WRITE_UNCORRECTABLE_EXT command                             
           *    {READ,WRITE}_DMA_EXT_GPL commands                           
           *    Gen1 signaling speed (1.5Gb/s)                              
           *    Gen2 signaling speed (3.0Gb/s)                              
           *    Native Command Queueing (NCQ)
           *    Phy event counters
                Device-initiated interface power management
           *    Software settings preservation
           *    SMART Command Transport (SCT) feature set
           *    SCT Long Sector Access (AC1)
           *    SCT Error Recovery Control (AC3)
           *    SCT Features Control (AC4)
           *    SCT Data Tables (AC5)
                unknown 206[12] (vendor specific)
Security:
        Master password revision code = 65534
                supported
        not     enabled
        not     locked
        not     frozen
        not     expired: security count
                supported: enhanced erase
        100min for SECURITY ERASE UNIT. 100min for ENHANCED SECURITY ERASE UNIT.
Logical Unit WWN Device Identifier: 5000c5000b9cef47
        NAA             : 5
        IEEE OUI        : 000c50
        Unique ID       : 00b9cef47

i don't see a big "problem". or is it perhaps only the harddisk??

lg
papierschiff

djgera · 2009-05-09 15:17:57

what shows a "filefrag /home/hanna/temp/bigfile.txt" ?

papierschiff · 2009-05-09 16:07:01

23754 extents found, perfection would be 11 extents

what means this?

djgera · 2009-05-09 16:12:09

That is the problem, the file is fragmented in 23754 parts (or is a sparse file) you can see the real size with du -sh /home/hanna/temp/bigfile.txt and compare with ls -lh /home/hanna/temp/bigfile.txt

What is your filesystem? if you use XFS you can run (as root) "xfs_fsr -v /home/hanna/temp/bigfile.txt"

papierschiff · 2009-05-09 16:13:21

ok, this make sence. its ext3, i thought i don'T neet fragmentation with etx?

djgera · 2009-05-09 16:49:45

Under some conditions the filesystems don't fragment much (*ideal world*), but when these rules are break (for example the free space is below 20%) new files stored may be become fragmented. In the *real world* files are always fragmented in differents levels.

If you have suficiente space, you can try copy the file to another location, delete original, and then move again. This should be ideally with an special copy, that avoids fragmentation, but you can try with a simple "cp" if reduces at least some fragments.

Try this:

filefrag fragmented-file
cp fragmented-file fragmented-file.new
filefrag fragmented-file.new #now compare if the fragmentation is reduced

papierschiff · 2009-05-09 17:18:51

hm, i have 150GB free, this should be enough free space. when i copy there are "only" >4000 extends.. -but i see, now it is a little faster with dd: 78,5 MB/s

i will try the tool skake or will copy all files to an extern HD and copy it back..

thanks for your help

Arch Linux

#1 2009-05-09 14:36:13

slow read hd performance..

#2 2009-05-09 14:52:35

Re: slow read hd performance..

#3 2009-05-09 15:02:34

Re: slow read hd performance..

#4 2009-05-09 15:17:57

Re: slow read hd performance..

#5 2009-05-09 16:07:01

Re: slow read hd performance..

#6 2009-05-09 16:12:09

Re: slow read hd performance..

#7 2009-05-09 16:13:21

Re: slow read hd performance..

#8 2009-05-09 16:49:45

Re: slow read hd performance..

#9 2009-05-09 17:18:51

Re: slow read hd performance..

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