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I'd need a NAS - Network Attached Storage - and apart the fact that it has drives inside and serve as file storage, I didn't know anything more really... so I made my homeworks, as usual, and a whole new world opened!
I thought it was easier - put the drives in, plug it to the PC and/or internet, and you presto! You are ready to go.
Not so fast, amigo!
Even if it's a matter of minutes to setup the basic settings, first question is: which NAS?!?
Almost everyone may agree that the most known and reliable brands are Qnap and Synology - someone would add Thecus, but here in Europe most, including me, never heard about it. That's it, only two main brands to choose from, what's the problem?
Apart that there are literally dozen brands around, some with even better price/quality ratio, I thought it's "better safe than sorry"... read many horror stories about other brands NASes that literally "eat" drives like candies, one after the other!
I also thought about using an old server - you know, the ones with A LOT of drive slots, like 12 or more... prices are quite affordable, often half or less the price of a NAS with the same number of bays. Not a wrong idea, per se, but... power consumption if several times more, so running one server 24/7 year round would cost in a year more than the difference of its price compared to normal NAS - so the break even point is only one year, and I hope that a good NAS would last more than that!
OK, were where I? Yes, no server - good idea but too expensive in the long run - so NAS, Synology or Qnap.
Now, several questions arise: brand new or used? Fresh used, or vintage? How many bays? Which RAID to set up? Which model? What processor? Which drives to use? What capacity?
New or used? Well, it depends on our budget, of course! I'm always keen to spend the same price for a top-of-the-line full fledged top model used, instead of a barebone basic new one. Sure, the new one has warranty, advanced technology, but as always "it depends"...
I'd go with used, then; but, fresh or vintage? Again about budget: if a fresh used one may be found for a nice price, let's take it; problem is, it seems that recent models retain high prices - I took a look around, and usually a two/three years model used is only 20% less than new... not worth it. Then vintage? Yep, is it possible to find them at dirty cheap price, but beware: they have several limits!
One, of course, is the speed: the oldest ones used ARM processor, with limited power and small memory; but the worst limit is capacity: some are limited to few TBs, while the best could top 16TB; not that bad, at the end; first problem is to find compatible drives (according to brands own compatibility list, they are limited often to 4/6TB drive), then, if you find the right size, when you need more storage space, you must buy a new NAS.
So, "in medio stat virtus"; an old model, still not vintage, would do: one with an Intel CPU - Atom, Celeron, Xeon, i3 etc. with no size limit could be a perfect balance between price and performance! The 16TB limitation is due to 32-bit operating system, but some intermediate model can use newer firmware to override this when a new array is made - but not when migrating to a different RAID version or adding more drives, so beware!
How many bays? Well, this is strictly related to the RAID configuration that we want to use. RAID 0 is the fastest, but if (when) a drive fails, all the data are lost! It must be used only for temporary content that must be served fast. After that, you could use RAID 1 - fast, but needs more drive; the only other choice apart the former using a 2 bay NAS.
What to use then? For small drive size and/or drive number, RAID 5 is a good compromise - you'll get N-1 drive capacity (for example using four 4TB drives you get (4-1)x4TB=12TB); the biggest disadvantege is that it could take literally days to rebuild the array if (again, when) a drive fails, and the biggest problem is, what if meanwhile another drive will fail? Not a so remote possibility, thinking that most likely all drives used there are of the same model/size (or even worst same batch); in that case, say farewell to your data...
Then RAID 6 is a better compromise if one wants to be more than sure (still, not 100%, but maybe 99.999%) that if something will go wrong, you'll not lose the data. It uses not only one reduntant drive, but two or more; so in our previous case of four 4TB drives, the whole capacity will be reduced to only 8TB; but in the not-so-impossible case that a second drive will fail during the array rebuild, you will not lose your data. Sure, then if a third drive fails... you must be the most unlucky person in the world (unless you set up three redundant drives...)
Back to bays: one, absolutely not, useless; no data protection at all. Two is the bare minimum, but in any case the total capacity is halved. Three, then? Well, you can use RAID 5 so better three than two; still, with four you can use also RAID 6 - if you need stronger data protection or you feel particularly unlucky! Then four bays - at least!
Models: too many to list here, and each model adds usually only a bit on top of the previous one, so better to carefully check technical data and then decide; for example, there are some models that have the same features of a more expensive one, but the display; do you really need a display in a NAS? It may be useful if you have to set it up without a PC, but who has not a PC nowadays? And the few ones without would probably not need a NAS anyway, so...
Processor, I've written before: an Intel one, the best/fastest model you can afford. Memory, again, the more, the better. A note: there are some models that use M.2 as read/write cache: this could improve a lot speed when using random small files, like database; still, almost useless serving big files on FTP.
Drives: avoid the desktop version, in particular low RPM (the so-called green); albeit perfect for home use, they are not made for sustained used, always on for several years! Then, the best would be enterprise, and NAS versions; also surveillance are better than desktop. WD or Seagate are the most used - possibly not only because of their quality, but also of their brand or compatibility, who knows... also, apart those, who still produce mechanical drives? Toshiba, and then who else?
Check the MTBF and the warranty - some enterprise models have five year, while most of the others have three, like NAS or surveillance. Of course an hard drive, as much as any other electronic device, will fail one or two days after the warranty is expired, so take it in account!
Finally, capacity... back to "old models but not too much": if you want/need more than 16TB in the (next) future, it's better to spend a bit more now, and put bigger drives, than discover that you can't add more drives without being forced to backup everything!
TO BE CLEAR: a RAID 1/5/6/10 is NOT a backup; sure, it is more robust than a single drive or JBOD/RAID 0, but there is always a chance that something could go wrong - someone that steal the NAS, a thunder that fries it, the cat that decide to pee on it because she does not like its smell etc. - then the best thing to do is to backup data routinely (depending on the refreshing data cycle) and possibly put the backup in another room/house/town/country/continent/planet/galaxy etc.
Which drive size then? Again, it depends... is the bigger the better still valid? Yes and no... personally I'd not use now 2 or 3TB drives - in a 4 bay NAS in RAID 5 you'll get only 6/9 TB total capacity - that you can have with two 6/10TB drives and RAID 1 even in a dual bay NAS. Then, 4TB is the minimum, I think. But again, remember the 16TB limit if your model is affected!
Let's see... 20TB drive price is quite steep; you can get 16TB ones for half price, so I'd take that size as maximum for now to be used in a NAS. Back to our possible four bay NAS, in a RAID 5 you can get (4-1)x16=48TB... not that bad! But... when (not if) a drive will fail, it will take I guess not only days, but weeks to rebuild the array... and the risk of a second drive failure is behind the corner! RAID 6 with 16TB will give you 32TB - only two thirds of RAID 5, but more robust data failure protection.
Still, do someone really need 32TB or even 48TB at home? Or more - what's about a twelve bay RAID 6 with 12x16TB for a gran total of (12-2)x16TB=160TB?!?
A budget conscious would probably go for "small" 8TB/10TB drives - a good compromise between space, cost, and rebuild time; for example, would it be better/cheaper/faster a four bay RAID 6 4x16TB=32TB, or a six bay RAID 6 6x8TB=32TB as well? If NAS price would be similar, I'd go for the second solution - cheaper main drives and spares, short rebuild price.
That's all, folks! Hope it could be useful for someone!
EDIT: forgot to mention: I was talking about tower/home NAS versions; rack ones are (usally) better versions due to build quality and often dual power supply - and they are more sexy, I must admit...
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