[oe-issues] [Bug 3070] New: udev: sync mount option causes extreme slow flash memory writes

[bugzilla-daemon at tinman.treke.net]

http://bugs.openembedded.org/show_bug.cgi?id=3070

           Summary: udev: sync mount option causes extreme slow flash memory
                    writes
           Product: Openembedded
           Version: Angstrom
          Platform: Other
        OS/Version: Linux
            Status: NEW
          Keywords: ARC
          Severity: major
          Priority: P2
         Component: Distributions
        AssignedTo: openembedded-issues at lists.openembedded.org
        ReportedBy: utx at penguin.cz


/etc/udev/scripts/mount.sh contains "sync" option to mount. Also default
/etc/fstab seems to contain "sync" option.

It causes extreme bad performance and raising R/W cycles for flash technology
devices (CF, SD, MTD). Please don't use it.

Technical description: sync write sends data to the medium as soon as possible.
Writing one sector to a typical flash memory requires erasing and reflashing of
64kiB region. Sync writing of 64kiB with 512B sectors could requires 128
reflashings (depends on flash firmware).

Example: Zaurus SL-C3200 is capable to transfer 2.2MB/s, card is capable to
transfer even more. Actual write speed is 50kB/s.

Proposed fix: Use "flush" (sync-on-close) instead of "sync" (always sync). Also
using of "noatime" and "nodiratime" could increase performance.

Related but about the same problem in SuSE Linux 10.0:
https://bugzilla.novell.com/show_bug.cgi?id=105871


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