Re: BBU still needed with SSD?

On 2011-07-19 13:37, Florian Weimer wrote:
> Is this "Total_LBAs_Written"?
I got the same name "Total_LBAs_Written" on an 5.39 smartmontools, which
was renamed to 241 Lifetime_Writes_GiB after upgrade to 5.42. Note that
this is smartmontools new interpretation of the values, which happen to
match with the OCZ tools interpretation (241: SSD Lifetime writes from
host Number of bytes written to SSD: 448 G). So for the Intels
it's probably also lifetime writes in GB but you'd have to check with an
Intel smart values reader to be absolutely sure.
> The values appear to be far too low:
>
> 241 Total_LBAs_Written 0x0032 100 100 000 Old_age Always - 188276
> 242 Total_LBAs_Read 0x0032 100 100 000 Old_age Always - 116800
>
> 241 Total_LBAs_Written 0x0032 100 100 000 Old_age Always - 189677
> 242 Total_LBAs_Read 0x0032 100 100 000 Old_age Always - 92509
Hmm that would mean 188TB written. Does that value seem right to your
use case? If you'd write 100MB/s sustained, it would take 22 days to
reach 188TB.
> The second set of numbers are from the drive which wears more quickly.
It's strange that there's such a large difference in lifetime left, when
lifetime writes are so similar. Maybe there are more small md metadata
updates on the second disk, but without digging into md's internals it's
impossible to say anything constructive about it.

Off-topic: new cool tool in smartmontools-5.4x:
/usr/sbin/update-smart-drivedb :-)

--

Yeb Havinga
http://www.mgrid.net/
Mastering Medical Data