Re: SSD Analyzer Tool

He had a drive fail. We have no idea if it was a memory cell that failed,
a full memory chip, the controller chip, the SAS interface chip, the buffer
memory chip, or some other piece. Also, there are typically 4-10 memory
chips on an SSD; if 1 chip failed v. just a cell then it would probably
take out enough space that the drive couldn't compensate.

As to having the extra cells, they are actually used for performance with
added reliability being a side benefit. Writing a normal cell is a read
cell/update buffer/erase cell/write cell operation, but cells in the spare
area are already erased so only a write is needed to store the data (the
cell being updated is mapped to the new cell & the old cell is put on the
list of cells to garbage collect). So the extra cells aren't a reserved
area so much as cells that wind up scattered all over the memory chips over
time. Depending on the drive's firmware & OS, the garbage collection of
used cells - where they're erased & prepped for future writing - occurs
when the drive is idle or the OS issues a TRIM command.

BTW, traditional platter drives have spare tracks where data on sectors
that are going bad can be remapped:
http://en.wikipedia.org/wiki/S.M.A.R.T.#Known_ATA_S.M.A.R.T._attributes(see
ID5 in the table).

On Sat, Dec 3, 2011 at 1:35 PM, Joe Pluta <joepluta@xxxxxxxxxxxxxxxxx>wrote:

Here's what I don't understand. Rob says he replaced a drive because it
reported FAILED. I didn't get the sense that there were any warnings,
it just fell over. Now, if the whole idea on these drives is that they
have a bunch of extra space that they use to replace failed blocks,
wouldn't it make sense that:

A. You would have a way to see the amount of "extra" space remaining on
a drive.

B. The drive would warn you as it was losing it's extra space. Say send
a message to the system operator when a drive uses 50% of it's spare
storage, then another at 75%, 90% and every 1% after that.

I'm not a hardware guy, but that would make sense, wouldn't it?

Joe

Joe,

I know there's been A LOT of people leaving the midrange ranks over the
years, but my more than ample gutt tells me that the problems of the

9335(?)

drives failure rates is still a stink that IBM works hard to avoid in any
"disk" technology it releases...

DR2

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