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 I may be out of date, and I've heard bad comments about xfs too ...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>
