Opinions: ECC on SSD

[gribs]

I haven't seen a lot of SSDs with this feature on their description. I know what it does for RAM, so I figure it would be useful, but I wasnt sure how much so here I am inquiring..

I was looking at Mushkin's SSD line for a while and wondering if its worth throwing down on a Chronos or some other brand of SSD with ECC as a factor above performance?

 

[Dereck47]

ECC is not a factor in SSD performance. It's used by all NAND chips in all SSDs for bad block management.

Here some info from Wikipedia:

NAND flash architecture was introduced by Toshiba in 1989. These memories are accessed much like block devices, such as hard disks or memory cards. Each block consists of a number of pages. The pages are typically 512 or 2,048 or 4,096 bytes in size. Associated with each page are a few bytes (typically 1/32 of the data size) that can be used for storage of an error correcting code (ECC) checksum.

NAND relies on ECC to compensate for bits that may spontaneously fail during normal device operation. A typical ECC will correct a one-bit error in each 2048 bits (256 bytes) using 22 bits of ECC code, or a one-bit error in each 4096 bits (512 bytes) using 24 bits of ECC code. If the ECC cannot correct the error during read, it may still detect the error. When doing erase or program operations, the device can detect blocks that fail to program or erase and mark them bad. The data is then written to a different, good block, and the bad block map is updated.

Most NAND devices are shipped from the factory with some bad blocks. These are typically marked according to a specified bad block marking strategy. By allowing some bad blocks, the manufacturers achieve far higher yields than would be possible if all blocks had to be verified good. This significantly reduces NAND flash costs and only slightly decreases the storage capacity of the parts.

Here's the link for detailed info: http://en.wikipedia.org/wiki/Flash_memory

Look at NAND types rather than ECC when researching SSDs:
Asynchronous NAND = Good
Synchronous NAND = Better
Toggle NAND = Best

 

[gribs]

Best answer selected by gribs.

 

[gribs]

Well, that cleared things up. Although I didn't intend to relate ECC to performance, I guess I worded that sentence unclear.

Thanks.