Difference between revisions of "TS-4710 DoubleStore"

From Technologic Systems Manuals
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The default SD image is 3GB which is designed to fit in a dual-card Doublestore configuration.  When dual card doublestore is used it stores the same image on both cards and also includes metadata and checksums for the entire image.   
 
The default SD image is 3GB which is designed to fit in a dual-card Doublestore configuration.  When dual card doublestore is used it stores the same image on both cards and also includes metadata and checksums for the entire image.   
  
You can use the [ dblstorctl] utility to work with DoubleStore on your Linux workstation.  The simplest way to get doublestore set up is to first take a backup of your SD image, and then use dblstorctl on a workstation to convert it:
+
You can use the [ftp://ftp.embeddedarm.com/apps/dblstorctl/dblstorctl-x86 dblstorctl] utility to work with DoubleStore on your Linux workstation.  The simplest way to get doublestore set up is to first take a backup of your SD image, and then use dblstorctl on a workstation to convert it:
 
<source lang=bash>
 
<source lang=bash>
 
export INPUTIMAGE="yourimagebackup.dd"
 
export INPUTIMAGE="yourimagebackup.dd"

Revision as of 09:47, 5 September 2013

This series supports DoubleStore which can be used to significantly increase the reliability of SD cards. This allows one SD image to be written to two cards allowing redundancy among both SD cards. See our white paper for more information on the concept. Development can take place with a single MicroSD card, but for using DoubleStore 2 MicroSD cards are used.

The default SD image is 3GB which is designed to fit in a dual-card Doublestore configuration. When dual card doublestore is used it stores the same image on both cards and also includes metadata and checksums for the entire image.

You can use the dblstorctl utility to work with DoubleStore on your Linux workstation. The simplest way to get doublestore set up is to first take a backup of your SD image, and then use dblstorctl on a workstation to convert it:

export INPUTIMAGE="yourimagebackup.dd"
eval $(stat -c "imgsize=%s" $INPUTIMAGE)
dblstorctl --primary ${INPUTIMAGE}.dblstor --fallback /dev/null --init --writeimg "$INPUTIMAGE" --size=${imgsize}B

This will output yourimagebackup.dd.dblstor which can be written directly to both SD cards:

dd if=yourimagebackup.dd bs=4M conv=fsync of=/dev/sdb # replace sdb with your SD card device

The board will boot the same using the DoubleStore MicroSD cards, but sdctl includes additional information:

# sdctl --stats
nbdpid=338
nbd_readreqs=1508
nbd_read_blks=95490
nbd_writereqs=0
nbd_write_blks=0
nbd_seek_past_eof_errs=0
sdcard_resets=4
read_seeks=1261
write_seeks=0
size=0x641800
humanized_size=3.35GB
fb_offset=-6559744
primary_tainted=0
primary_failed=0
fallback_tainted=0
fallback_failed=0
resilver_pct_done=0
lifetime_write_blks=59038888
humanized_lifetime_write_blks=30.22GB
errors=0
unrecoverable_errors=0
conflicts=0
fallback_configuration="separate disk"

fallback_configuration should read "seperate disk" when booting doublestore correctly. For diagnostics, the tainted and failed settings are the most relevant:

primary_tainted=0
primary_failed=0
fallback_tainted=0
fallback_failed=0

When a card is tainted, the LED near the card will begin to blink. This indicates Doublestore has seen the card perform an unexpected behavior that DoubleStore was able to correct.