Data Recovery Weekly

If you delete a Storage Spaces pool on a TRIM-capable SSDs, the entire pool gets trimmed, as in poof!, gone .

Circa 1998, AMD used a "Performance Rating" or "Pentium Rating" (PR) to indicate their CPU's performance by comparing it to then-current Intel Pentium. That was mostly because AMD could not deliver a CPU operating at frequencies matching these of Intel's, so they opted to move frequencies out of sight. Then, comparison shopping became little messy. And btw that did not help AMD much. Given this thread on AnandTech , looks like we might get a similar issue with SSD benchmarks. Not that I particularly care about SSD benchmarks.

Reading the article on NTCompatible as they test data recovery software and fail to recover data from TRIM-enabled SSD (which is pretty much the expected behavior), I see they're a little bit puzzled because some data would still remain even on a TRIM-enabled SSD. Interestingly, some traces to specific data remained, and that's one oddity I don't quite understand. The answer is actually pertty simple - these were NTFS resident files. On NTFS, when the file is deleted, its MFT record is marked "free, available for reuse", but never actually relinquished back to the free space. Because NTFS uses MFT entry numbers internally to address a parent-child relationships. Removing one entry would require an entire volume to be reunmbered, which is cost-prohibitve. So, the data outside MFT is zero-filled immediately once TRIM command is issued. The MFT entires however remain unchanged. This explains they were able to get file names and correct file sizes, but the dat...

You can only align a partition (on a hardware block boundary) if a cluster size is an integral multiple of your hardware block size. This means you cannot align a HFS partition, because it would happily use 19 or 27 sectors per cluster. Most other filesystems would use a cluster size that is a power of two, matching the hardware block size. Another thing is that if the boot sector and the data area use different alignments, it is the data area that you align. On FAT, there may be 1025 or whatever odd number of sectors between the boot sector and the first cluster of actual data. If you align the FAT partition's boot sector, the data would then be offset by one sector.

TRIM wins. The TRIM command available on modern SSD reduces the chances to successfully undelete a file. TRIM violates the most significant principle of the data recovery that “the data is not overwritten until the disk space is actually required to store another piece of data”. Writing on a SSD is slower because before writing something to the block, it's needed to erase this block, and the erase operation is relatively slow. This is responsible for the performance degradation effect of the SSD when the performance starts to degrade as the device is filled to capacity, because there are no more blank blocks on the SSD. To compensate for this performance degradation, a hardware command TRIM was implemented to erase the specified blocks in advance. TRIM is supported by most modern high capacity SSDs. TRIM is commanded by the OS (supported starting with Windows 7). When Windows 7 is in the idle state, it commands TRIM to erase those blocks which are not in use any longer. TRIM violat...