Re: Very slow transfers to/from micro SD card on a RPi B+

[Jean-Baka Domelevo Entfellner <domelevo%gmail.com@localhost>]

Hello,

Sorry for my late answer on this, but in any case the alignment seems
correct here:

rpi# fdisk ld0
Disk: /dev/rld0c
NetBSD disklabel disk geometry:
cylinders: 7729, heads: 128, sectors/track: 63 (8064 sectors/cylinder)
total sectors: 62333952, bytes/sector: 512

BIOS disk geometry:
cylinders: 1024, heads: 255, sectors/track: 63 (16065 sectors/cylinder)
total sectors: 62333952

Partitions aligned to 2048 sector boundaries, offset 63

Partition table:
0: Primary DOS with 32 bit FAT - LBA (sysid 12)
    start 8192, size 114688 (56 MB, Cyls 0/130/3-7/165/30)

On Thu, Jul 9, 2015 at 5:53 PM, Michael <macallan%netbsd.org@localhost> wrote:
> Hello,
>
> On Thu, 9 Jul 2015 11:28:17 +0200
> Jean-Baka Domelevo Entfellner <domelevo%gmail.com@localhost> wrote:
>
>> Hi there,
>>
>> I'm currently untarring a pkgsrc.tar.gz (48MB) to /usr. The
>> commandline I used is:
>> # nohup tar xfz pkgsrc.tar.gz -C /usr &
> ...
>> It's on average between 0.20 and 0.25 MB/s, don't you think it's
>> unreasonably slow? Do you have any piece of advice for me?
>
> It should write at least 1MB/s. Is the partition you're writing to
> aligned to something like 16MB? Really odd alignments ( like, less than
> a filesystem block ) will force the card to do lots and lots of
> read-modify-write cycles which will slow it to a crawl.
>
> have fun
> Michael