On 2015-09-29 04:00, dominik...@openmailbox.org wrote: > On 2015-09-28 20:15, Stuart Henderson wrote: >> On 2015-09-28, dominik...@openmailbox.org <dominik...@openmailbox.org> >> wrote: >>> I'll use a 500GB SATA drive for the OS installation and will setup two >>> WD Red drives in mirror using softraid(4). >> Any particular reason not to just put the OS on the mirrored drives? > Good question. Thought it was preferable to isolate one from another.
There is no point nowadays, unless you intend to be able to break loose the mirrored drives from the system at some point and use them stand-alone or in another system, while still operating the first server. In the past, there were for example limitations on booting from raided volums, which I suspect is where this misconception stems from. Now there is no problem. >>> A bunch of people (on a certain FreeBSD based NAS forum) chastise users >>> who lost data for not having backed up their NAS. Well, isn't your NAS >>> already a backup? Of course, I'm talking about a home NAS here where the >>> content is only occasionally accessed. Is it me that's mixing up the two >>> responsibilities, file server and backup server when I shouldn't? >> Take a different view: Mirrored drives and RAID are not really for data >> protection, they're so you can keep operating in face of (some types of) >> hardware failure. > > Indeed, but in reality doesn't it do both? Absolutely not. :-) As Stuart and others points out, you should look at this from another perspective; from what I can deduce from your description you are building a home server for the family to share data on. That is absolutely excellent! There is no need for each of you to carry your favourite movies and music around on your individual workstations/laptops/ipads/phones/toasters when you can store them once, centrally. However, even with mirrored drives, IT IS NOT A BACKUP. What if there is a fire? What if someone burglars your house and steals the server? What if someone accidentally knocks it over and all disks in it are damaged by G-force overload? As Stuart says, mirroring is redundancy for OPERATION, not for backup. In other words, if your system is mirrored your server won't go offline if one disk dies on you, but will give you time to replace the drive and re-mirror it before the other one goes too. If you want to set up a combined home server/backup solution, it would in fact be better *not* to mirror your two drives, but to use one for your server needs and the other for backing up what's on the first. Of course, that still only takes care of two of the scenarios - drive failure and operator/software failure, i e accidentally removing or overwriting files. In a fire, all of your movies, tv series, music, documents, digital photos and home videos will be just as gone forever as with mirroring. Look at this as your new home server for family file sharing. THEN look at a backup solution, too. One with geographical redundancy, which is absolutely crucial. That is, somewhere else but in your home. But don't just do one without the other, because it WILL make you sorry in the end. >> Now, if you're intending to use this server to put a *second* copy of >> your files onto from some other machine, always keeping another copy, >> then mirrored drives might be good enough for you. But it involves a >> lot more discipline than setting up some automated backup schedule, >> and it means treating it differently than "the machine that you store >> files on". > > The files are currently strewn over a couple of machines all over the > house. > I intended on deleting them once pushed to the server but maybe I should > keep them > at least on my desktop once they're tidied up. Here's where your plan becomes crucially flawed. The moment you have only one copy of something, it IS NOT BACKED UP. And data on mirrored disks always counts as *ONE* copy only. Always. And, I would also submit that as long as you only have something in only one PHYSICAL location, it is not backed up either. In my business (and personally) I always have at least three copies of every single piece of data on all of my systems. For example, I have systems in three different data centers, and every single system except the backup servers themselves is backed up every single night to all three places. And in addition to that, I keep a fourth copy of everything at home, also nightly backed up. All of those 20+ servers are also either mirrored or use RAID5. Most of them also have redundant power supplies and are connected with two network interraces via trunk aggregation/link failover to two separate switches, but those measures are ONLY to protect from common hardware failures, to keep everything online. Never ever make the mistake of putting an equal sign between raid and backup. >>> Would you suggest going more for a Supermicro X10 motherboard with a >>> separate CPU that could be upgraded down the line (if need be)? I'm also >>> hesitating between this and a much cheaper Biostar 1037U Celeron based >>> embedded motherboard, but weren't sure of the quality for something that >>> would stay on 24/7. >> I wouldn't be too concerned about ability to do CPU upgrades later. >> If you run out of performance, rather than getting rid of the old CPU >> and adding a slightly faster one at quite a lot of expense, at that >> point you could get another little machine and split off some of >> those public/semipublic services. I agree with Stuart here, too. I can't recall a single time the last... idk, 15-20 years, when I have actually upgraded a CPU on a system, or added a second one either for that matter (with the exception of big-iron Sparc-, Power- or Alpha-based servers back in the day, but that was... well, not recent :-) ). However, memory (and disk) upgrades do happen now and then, so buying a system that can expand RAM for future needs might make sense. Especially now when everyone are virtualizing their environments, running virtual servers quickly eats up your RAM. On the other hand, there is always a certain window of opportunity when it is reasonable to buy RAM upgrades. When you are one or two generations of memory development removed from the current state of the art, it just won't be worth it because old memory modules becomes prohibitively expensive. For example, try to find cheap DDR2 memory today! I can buy 64 GB (4x16 GB) DDR3 or DDR4 Reg-ECC memory for less than I can buy 16 GB of DDR2 memory for. Regards, /Benny
