[mythtv-users] apc backup

[Mike Thomas]

On Sun, 20 Mar 2016 21:04:34 +0000
Simon Hobson <linux at thehobsons.co.uk> wrote:
> David Williams <mythtv_david at yahoo.com> wrote:
> 
> > I'm posting to this group v. APC since my issue is mythtv-related.
> > 
> > Spring rains generally manifest in power outages in my area with
> > disastrous consequences. On more than one occasion my hard drive
> > has been corrupted to the point where with my existing skill set I
> > found it impossible to resurrect. It seems like BIOS was more
> > forgiving than UEFI.
> 
> Different filesystems are more forgiving than others - but I've
> generally had few problems with EXT3 (yes I'm a bit old fashioned !)
> which will generally recover by just rolling forward the journal.
> Other tricks can make problems "less troublesome". For example, while
> it's one of those hangovers from the days of LILO and BIOSes that
> couldn't access past a few hundred meg of disk, having a /boot on
> it's own filesystem should generally mean that you can get to a
> busybox shell if your root filesystem is damaged. From there, fsck
> will usually get your root filesystem going and from then on things
> get easier.

Dear David,

I second this advice. Put /boot in a separate slice. Put your database
on a separate slice. Put your videos on a separate slice. Problems
should they occur can be resolved in isolation.

You should do backups.

Contrary to Simon, I prefer ext4 for everything but perhaps your video
files. I have found corruption to be very rare on my computers since I
moved from ext3 to ext4, even on my development boxes (which get
terrible abuse). I suspect it comes about because ext4 uses extents to
store files. This means files and their supporting data structures are
smaller and less fragmented. It offers significantly increased
performance for the same reason. Other people have different
experiences.

The most important thing is not to disable barriers. Having said that,
I run many development computers without any barriers, and with
fast-and-loose options like journal_async_commit, and they still
perform admirably when given a gratuitous ~#b. It never ceases to amaze
me.

I can't recommend XFS for general use. It's recovery process is
topsy-turvy. You have to mount a corrupted volume to apply the journal,
before unmounting it and xfs_repairing it, unless someone knows a
better way.

> > In an effort to head off another round I purchased an APC 750
> > Backups. I set this up with the apcupsd app and it shuts down just
> > great. My question is this: I used the stock settings with the
> > exception of Battery level which I changed from 5 to 30. I welcome
> > any and all advice on these settings. 

Let me tell you a story about my APC UPSes...

I have a few APC UPSes. Aside from having several important design
flaws, these UPSes suffer from having a worthless guarantee. I had a
fault on one of my UPSes so I rang APC's technical support line. It was
only seven months old, and thus still within warranty, or so I thought.
I was astounded when the conversation went like this:

Me: The problem is that the such and such a light flashes to indicate a
battery failure. I tried swapping the batteries between my UPSes and it
clearly isn't the batteries. There's something wrong with one particular
UPS.
Support droid: Ah, you turned it on?
Me: Yes. How else do I use a UPS?
Support droid: Well, sir. You have voided your warranty.
Me: You are kidding me?
Support droid: No, sir. Your UPS is damaged. It has had a power surge.
Me: What do you mean?
Support droid: Power surges come down the electricity cables and blow
them up. They are excluded from the warranty.
Me: So, what you are telling me is that if I plug in one of your
products I will damage it and void the warranty?
Support droid: Yes.

I am not making any of this up.

Add to that the following laughable problems (not all of which are
peculiar to APC UPSes):

- They run the batteries far too hot. They are jammed next to a hot
  transformer all their lives. Batteries subjected to this kind of
  abuse (a word used by battery manufacturers) can be expected to fail
  in a year. Two if you are lucky. This has been my experience over many
  years. As far as I can see this is a money-making scam. They are
  getting away by telling people that batteries only ever last a year
  or two, so they should expect to shell out 3-500 quid a time on
  batteries.

  I have now mounted my batteries in an external enclosure. My
  batteries now last as long as the battery manufacturer claims. 5 or
  10 years according to the type of battery. I use compatible Yuasa
  batteries, but I managed to keep the APC own-brand batteries for
  three years outside the hotbox.

- At full load the discharge currents are often quite high for pokey
  batteries in hot enclosures. This is another way to reduce battery
  life. A shorter run time will lessen the damage.

- They are incompatible with generators. They switch off, on, off, on,
  off, on until they blow a fuse. They create huge voltage spikes
  whilst doing this.

Like you I bought APC UPSes for home/office use. APC are a toy
manufacturer. Nobody relies upon them for anything but home use, or at
least I hope they don't. You get what you pay for.

I spoke to some professional UPS manufacturers. They chuckled at my
story, then they said, well, what do you expect from a toy? APC UPSes
are designed to perform a controlled shut-down of a small number of
computers in a home environment. Set them to shut down after one minute
without power and be glad of that, but never ever rely on them. For one
thing, their battery capacity testing is hopelessly unreliable. You can
think that everything is going just fine and then a year after you
changed your batteries, but long before the UPS claims your batteries
are knackered you have a power cut. Guess what? The UPS dies on you.
Professional UPSes will do sensible battery capacity tests, but then
professional UPSes don't cook their batteries.

I took their advice and I start my shut-downs (I have several computers
which need to be taken down in order) after a minute. They have worked
fine for years, despite their warranty having been voided by being
plugged in.

I am fine with having a small number of shit UPSes. I live with it.
Home computers are not critical.

YMMV,

Mike