Re: recommendations for supported, affordable hardware raid controller.
On Saturday 02 January 2021 11:08:52 Richard Hector wrote:
> On 3/01/21 12:24 am, Andrei POPESCU wrote:
> > On Sb, 02 ian 21, 01:40:14, David Christensen wrote:
> >> On Linux (including Debian), MD (multiple disk) and LVM (logical
> >> volume manager) are the obvious choices for software RAID. Each
> >> have their respective learning curves, but they're not too high.
> >
> > An interesting article I stumbled upon:
> > http://www.unixsheikh.com/articles/battle-testing-data-integrity-ver
> >ification-with-zfs-btrfs-and-mdadm-dm-integrity.html
>
> Hmm. It only talks about software raid in the context of RAID-5. They
> acknowledge that RAID-5 is 'frowned upon', but don't go into why, and
> say they think it's great. My take: once you've lost one disk, you
> have the same reliability as a RAID-0 (stripe) set of what's left -
> much less reliable than no RAID at all.
>
> I generally stick with RAID-1, but would consider RAID-10.
>
> > My take:
> >
> > If you care about your data you should be using ZFS or btrfs.
>
> Licensing issues and the resulting complications stop me using ZFS,
> and last I heard btrfs wasn't regarded as being as reliable as ext3/4
> or xfs (I generally use xfs).
>
> I may be out of date, and I've heard bad comments about xfs too ...
>
> > In case of data corruption (system crash, power outage, user error,
> > or even just a HDD "hiccup") plain md without the dm-integrity layer
> > won't even be able to tell which is the good data and will overwrite
> > your good data with bad data. Silently.
>
> I guess I need to investigate that. Any further references? I've had
> crashes and power outages and never noticed any problems, not that
> that means they won't happen (or even that they haven't happened).
> Does a journalling filesystem on top not cover that?
>
> Cheers,
> Richard
It should do an ok job IF you have a ups big enough to carry it till you
can do a gracefull shutdown. Or NUT can do it for you. In my case I have
a 1500WA APC ups, which carries everything but the printers for long
enough to get the 20 kw nat gas fired generac in the back yard
auto-started, 15 seconds max. When the overhead lights are off, I'm only
aware of a power failure when the generac has started as that reboots
the printers.
Without the UPS, a power failure just as the journal is being written,
has a possibility of being incompleted or contaminated, but that is a
pretty narrow time window. Milliseconds, and not very many by my SWAG. I
have 4 other machines running 24/7 here, only one has a UPS, and despite
the poor performance of my local power system, have not lost a byte to a
power failure on any of them using ext4 file systems.
Cheers, Gene Heskett
--
"There are four boxes to be used in defense of liberty:
soap, ballot, jury, and ammo. Please use in that order."
-Ed Howdershelt (Author)
If we desire respect for the law, we must first make the law respectable.
- Louis D. Brandeis
Genes Web page <http://geneslinuxbox.net:6309/gene>
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