Re: PostgreSQL on eMMC - Corrupt file system

On 09/02/17 23:00, Christoph Moench-Tegeder wrote:
> ## Thomas Güttler (guettliml(at)thomas-guettler(dot)de):
>
>> Is running linux with postgres on eMMC a bad idea in general?
>
> I'd say that running anything with a read-write load on eMMC will
> end in pieces. It's ok to occasionally write something, but a mixed
> load is not really what these things were designed for. The wear
> leveling can be quite basic, you never know when it's gonna happen
> (i.e. sudden power down can kill your filesystem - that's why disabling
> journaling is not a very great idea), and if your device is "mostly
> full" anyways, the wear leveling has not much space to redirect the
> writes to. Remember that some of those chips are sold mostly by
> price - that is, the hobbyist "embedded" devices get the cheapest
> chips. A safer bet would be adding an external storage; some
> 64GB SATA SSDs are available for less than 50€ (perhaps it's better
> not to go for the cheapest ones here, too).

I agree, but three additional comments. First, we've got a fair number
of RPis running their root filesystems on the internal SD-Card without
problems, but the one Odroid which runs an eMMC card failed a few weeks
ago. Second, a useful precaution is to put stuff which will be updated
on an external device, although the same longevity concerns apply if
it's Flash-based. Third, experience here suggests that reliability
/might/ be improved if you fully zero a device before partitioning it to
make absolutely sure that the internal controller has touched every block.

--
Mark Morgan Lloyd
markMLl .AT. telemetry.co .DOT. uk

[Opinions above are the author's, not those of his employers or colleagues]