TS-4710 DoubleStore: Difference between revisions
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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 [http://www.embeddedarm.com/about/resource.php?item=628 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 | 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: | ||
<source lang=bash> | |||
export INPUTIMAGE="yourimagebackup.dd" | |||
eval $(stat -c "imgsize=%s" $INPUTIMAGE) | |||
dblstorctl --primary ${INPUTIMAGE}.dblstor --fallback /dev/null --init --writeimg "$INPUTIMAGE" --size=${imgsize}B | |||
</source> | |||
This will output yourimagebackup.dd.dblstor which can be written directly to both SD cards: | |||
<source lang=bash> | |||
dd if=yourimagebackup.dd bs=4M conv=fsync of=/dev/sdb # replace sdb with your SD card device | |||
</source> | |||
The board will boot the same using the DoubleStore MicroSD cards, but sdctl includes additional information: | |||
<pre style="font-family:monospace,Courier New ;background:black; width:18cm; white-space: pre-wrap; white-space: -moz-pre-wrap; word-wrap: break-word; color:white; "> | |||
# 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" | |||
</pre> | |||
fallback_configuration should read "seperate disk" when booting doublestore correctly. For diagnostics, the tainted and failed settings are the most relevant: | |||
<pre> | |||
primary_tainted=0 | |||
primary_failed=0 | |||
fallback_tainted=0 | |||
fallback_failed=0 | |||
</pre> | |||
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. | |||
Revision as of 18:02, 23 August 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.