Re: Solid State Drives with PG

Gordan Bobic wrote:
> John R Pierce wrote:
>
>> all the enterprise SAN guys I've talked with say the Intel x25 drives
>> are consumer junk, about the only thing they will use is STEC Zeus,
>> and even then they mirror them.
>
> A couple of points there.
>
> 1) Mirroring flash drives is a bit ill advised since flash has a
> rather predictable long-term wear-out failure point. It would make
> more sense to mirror with a mechanical disk and use the SSD for reads,
> with some clever firmware to buffer up the extra writes to the
> mechanical disk and return completed status as soon as the data has
> been committed to the faster flash disk.
Interesting, a few days ago I read something in the mdadm config about a
config for mirroring over 'slower' links, and was waiting for a proper
use case/excuse to go playing with it ;-) (looking up again)...

       -W, --write-mostly
              subsequent  devices  lists  in a --build, --create, or
--add command will be flagged as 'write-mostly'.  This is valid for
RAID1 only and means that
              the 'md' driver will avoid reading from these devices if
at all possible.  This can be useful if mirroring over a slow link.

regards,
Yeb Havinga