fsync tests - Mailing list pgsql-admin

From RBN
Subject fsync tests
Date
Msg-id AANLkTilma41XqdLfA-yCaUQCUfC5u8wDGOGzWnY2R8jN@mail.gmail.com
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Responses Re: fsync tests
Re: fsync tests
List pgsql-admin


I ran test_fsync on a local ext 3 partition and on a raid jfs SSD array 8x32GB RAID10.  The local disk returned quickly and gave what looks like acceptable results.  However, the RAID looks pretty bad.  Any one have any idea why fsync would take so long on an SSD RAID 10.


LOCAL DISK
Simple write timing:
    write                    0.005460

Compare fsync times on write() and non-write() descriptor:
(If the times are similar, fsync() can sync data written
 on a different descriptor.)
    write, fsync, close      0.072429
    write, close, fsync      0.075627

Compare one o_sync write to two:
    (o_sync unavailable) 
    (o_dsync unavailable) 
    write, fdatasync         0.075907
    write, fsync,            0.076320

Compare file sync methods with 2 8k writes:
    (o_dsync unavailable) 
    write, fdatasync         0.108367
    write, fsync,            0.108659



RAID 10 SSD jfs
Simple write timing:
    write                    0.004843

Compare fsync times on write() and non-write() descriptor:
(If the times are similar, fsync() can sync data written
 on a different descriptor.)
    write, fsync, close     95.546382
    write, close, fsync     51.407276

Compare one o_sync write to two:
    (o_sync unavailable) 
    (o_dsync unavailable) 
    write, fdatasync        10.999764
    write, fsync,           80.696959

Compare file sync methods with 2 8k writes:
    (o_dsync unavailable) 
    write, fdatasync       111.931881
    write, fsync,           99.329298


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