On Wed, Jun 05, 2013 at 07:33:31PM -0700, ravim wrote: > Our application writes a data packet to SD-Card as soon as it receive on > EXP board. The packet size is 40Bytes and may increase more. The binary data > is stored in files on SD card which we later run through our interpreter. > Now if someone pulls the SD-Card in midst of write operation what will > happen? > > I wanted to ask - is it possible that portion of data packet may be written > to file when SD card is suddenly pulled out? Because if this happens the > whole series of binary data will not make any sense or may give us totally > wrong information. > > If this happens how do we handle it? Is there a way to make this write > operation atomic??
If you mean that you're writing a sequence sectors to an SD-card, you could ensure that your sectors contain a checksum. If the write fails, the checksum will (with high probability) not match, and you can ignore the sector. This assumes that a write failure affects only the sector to which you're writing. A sensible flash translation layer would hopefully provide this guarantee. If you're writing to a file on a VFAT filesystem, it's different. You might be able to implement a transaction system by making use of the redundant FAT copies and doing shadow-paging with unused clusters. This would only guarantee consistency when reading from your own application though. Cheers, Daniel -- Daniel Beer <dlb...@gmail.com> www.dlbeer.co.nz IRC: inittab (Freenode) PGP key: 2048D/160A553B ------------------------------------------------------------------------------ How ServiceNow helps IT people transform IT departments: 1. A cloud service to automate IT design, transition and operations 2. Dashboards that offer high-level views of enterprise services 3. A single system of record for all IT processes http://p.sf.net/sfu/servicenow-d2d-j _______________________________________________ Mspgcc-users mailing list Mspgcc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/mspgcc-users
