[gentoo-user] Re: Safeguarding strategies against SSD data loss

[James <wireless@tampabay.rr.com>]

Rich Freeman <rich0 <at> gentoo.org> writes:


> > On 27/10/2014 11:24, Mick wrote:

> >>> With a caveat: if an ssd dies, it will die suddenly. Without warning.

With SSD the most important fact to keep constantly in mind is
writing/erasing by blocks due to uniqueness of the hardware.
Unfortunately, if you dig deeply, many Solid State Storage devices
are organized differently and those hardware differences may impact
your SSD_specific implementation  details. SSD raid redundancy is
something most machines (folks) cannot afford, imho and may be a waist
to dis_functional if you employ the same semantics for I/O on the
redundant SSD hardware.

[1] 
http://codecapsule.com/2014/02/12/coding-for-ssds-part-6-a-summary-what-every-programmer-should-know-about-solid-state-drives/


> >>  In such cases I am prepared to live with the risk of some
> >> data loss, on machines where raid is not an option.

Wise with a well thought out (planned) recovery/fresh-install strategy.

> > Without some form of redundancy that would be your best strategy -
> > decent and frequent backups


> But yes, backup and RAID are really your only options for SSD failure
> as far as I can see it. That and limiting the amount of data that
> can't be re-generated.  If you just save the world file and all of
> /etc you could probably rebuild a Gentoo install fairly quickly on a
> new drive, and then you're just left with /home and whatever else you
> happen to have installed that sticks stuff in /var that you care
> about.

Yep. Rich has it exactly right.  I'd add /usr/local/*
as by design that is where I put most uniqueness in any linux system
besides the list above.

In fact for small networks, I just identify the directories that I want
to preserve. At the least you rsysnc those to a differnet system
on the local net, besides a backup, if no raid is underneath. (Triple).
Obviously, you have all systems on UPS power......?

I'd add any dirs with custom scripts and the kernel  files also minimally
replicated to another system. A comprehensive list of critical files
is fine. Workstations and servers have different lists of critial files;
and you can further subdivide the servers by function, to focus
on those critical files and directories. So what is on the SSD that is
important, just replicate it to a spinning HD on the local net. None
of this replaces weekly backups, but give you a tertiary level of
recovery redundancy for the important stuff. Triple redundancy is keenly
important for all critical stuff; ymmv.

Personally, I find max-ram and spinning HD to be the best bang for the
buck. But, many folks with older portables are usually really happy with
SSD as a replacement (single) drive that is cost effective but needs
a network backup. 

[2]
http://serverfault.com/questions/454775/is-post-sudden-power-loss-filesystem-corruption-on-an-ssd-drives-ext3-partition


hth,
James