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SolFS recover from failure

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#1882
Posted: 12/15/2006 07:46:30
by Jure Bogataj (Priority Standard support level)
Joined: 05/23/2006
Posts: 35

Hello!

What options does SolFS provide when dealing with failures inside storage? Some questions that come to my mind:
- Is it possible and how that SolFS storage gets corrupted during read/write operations?
- What if some disk sectors gets corrupted and some portion of SolFS storage file lies on those sectors (e.g. you have 700MB SolFS storage file, and two 512-bytes sectors on disk are bad or unreadble). Does this mean that the whole storage is corrupted or can SolFS still access "non-corrupted" files and folders?

And one more question regarding structure and compatibility:
Is SolFS already made for 64-bit systems or is this meant to be done in a near future?

Thank you for your response!

Best regards,
Jure
#1884
Posted: 12/15/2006 11:04:50
by Eugene Mayevski (EldoS Corp.)

Quote
Jure Bogataj wrote:
- Is it possible and how that SolFS storage gets corrupted during read/write operations?


It's possible of course, both because of failures of hardware or because the operation is interrupted or because system cache is not flushed (for example when you pull of the USB flash drive without unmounting it).

There can be 2 kinds of corruption - corruption of the file data and corruption of the internal disk structures (i.e. supplementary pages, directories etc etc.). Corruption of structures will be detected when you attempt to access part of the disk. Corruption of file data will not be detected as SolFS doesn't have built-in integrity checking for the pages (you can implement one yourself if you use callback mode).

Also, damage can be media failure and data corruption. In case of media failure the attempt to read will fail and this will become known (so corruption of file data *will* be discovered). In case of data corruption, the file data damage won't be discovered (as said above).

Quote
Jure Bogataj wrote:
- What if some disk sectors gets corrupted and some portion of SolFS storage file lies on those sectors (e.g. you have 700MB SolFS storage file, and two 512-bytes sectors on disk are bad or unreadble). Does this mean that the whole storage is corrupted or can SolFS still access "non-corrupted" files and folders?


That's another problem. Attempt to read certain data will fail with error (see above). To recover the disk, one would then need to use CheckAndRepair() method. CheckAndRepair will attempt to recover as much as it can.

Quote
Jure Bogataj wrote:
Is SolFS already made for 64-bit systems or is this meant to be done in a near future?


what should be 64-bit? the code itself is compileable on 16, 32, 64 bit systems. File sizes are also 64-bit. Delphi interface is not 64-bit and most likely won't become one in any near future. C code of the engine is 64-bit. We didn't test the code of the C++ wrapper with 64-bit systems, but there should be no problems.


Sincerely yours
Eugene Mayevski

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