RAID 5: A few questions

[Crimson2006]

First, I'll explain why I think RAID 5 is best for me. I would value data security as my leading value but atlas, I'm not rich enough to sacrifice storage capacity for extra security. Ergo, I value both security and capacity equally. Performance, I would value read more than write, but in the macro view, I couldn't care less about performance. I'd be happy with 20MB/s for both read/write. Obviously, I just need to archive data that I would hardly use. I pick RAID 5 because it offers the best combination of both security and capacity.

I will now explain what I currently have and what I need storage wise. I have 10 external 3.5 HDD (including 5 built-to-be-external (BTBE) HDD considering if I can open them up and extract the HDD. i.e WD externals). It's just a blunderbuss of different specs. ranging from just about every type of HDD in use spanning 15 years...
Interfaces: PATA/SATA/SAS
Storage capacities from 120GB to 3TB
Speeds from 5400 to a single 10k

I seriously, at one point, had all of these running at the same time. The cables were a nightmare and have since retired all but my three biggest HDD which are BTBE which have sleep mode integrated so they are not constantly running. I don't expect to be able to use any of this in my RAID 5 build so I'll be buying all new HDDs and a 5-bay RAID tower to keep everything simple and reliable. I want either 10TB or 15TB of storage, depends if I have the money for the 15TB. Lastly, USB 3.0 or NAS, whichever is cheaper and simpler?

So, at this point, my questions begin. I included all of the info above hoping that I might be off about something, either my choice of RAID or the useability of my old HDDs in my quest for a reliable data solution.

#1: Seems as long as I limit multiple HDDs to least common size, I can have multiple HDDs in my RAID 5 build. I can understand that. But what about other factors? I plan on getting one size, one speed, and one interface; Respectively: 2Tb or 3TB, 5400 or 7200, SATA 2 or 3. But what about small things like cache or manufacturer? Or when push comes to shove and I need to replace a HDD factor no longer in production like the speed or SATA level (i.e 5400 speeds or SATA 2.0)?.

#2: Say I have 10TB of data and I need to rebuild the RAID. Say the processor allows 100MB/s for read/write (if that even matters?). How long would it take to rebuild the RAID. Not asking for an exact value. Just an estimate or a experienced value as I'm sure some of you guys have dealt with real RAID systems.

#3: Anyway to salvage some of the random HDDs I listed above without complicating matters by nesting similar HDDs together in a RAID 1 configuration? I've just recently came across possible ways including software: ZFS/Drive Extender and hardware: beyondRAID but have not yet thoroughly explored such options as I still have questions on RAID 5. I just feel like I can only know so little until I can experience it first hand and experiment with real hardware/software. JBOD is not applicable as I need both security and capacity. I have no need for extra storage beyond what is secure.

More questions may come up. Until then, please give me a greater insight to anything I may be lacking, be it knowledge, ideas, thoughts, etc...

Thanks for your time
-Crimson2006

 

[popatim]

to answer your questions (and 1 you didnt ask)

#0 - raid has nothing to do with data protection - thats the job of your backups. Raid is about keeping the system up in the event of a drive failure. Not losing all your data when a drive fails is a side affect but in no way protects the data. Things like the cat walking on your keyboard at the wrong moment and deleting everything is not something it can save you from. Ditto from viruses, angry spouses, stupid kids....
A backup is an extra copy of your files onto a different device. Preferable stored unpowered and not connected to anything at all so theres no way a voltage spike can cause damage.

#1 - Drive specs should match your interface type. For instance a NAS is limited by your network infastructure. If all you have is single gigabit then 5400rpm drives are fine. USB3 I would go with 7200rpm's. Cache size is irrelevant in raids. Stick with sata3 drives (they will work with sata 2 interfaces if needed). Theres no point in buying 5 old drives that aren't made anymore, what do you do when one fails since ideally you want identical drives in the raid... Avoid Green drives also.

#2 - depends on the Raid card you have. Plan on at least a week.

#3 - I would say use them as part of your backup plan.

 

[Crimson2006]

#0: How is not losing your data when a HDD fails and allowing you to rebuild, not protect the data? In this view, even backups do not protect data as they can fail when you hook them back up to recover lost data from another HDD that's failed... Absolute protection does not exist, only redundancy. Sure, backup trumps RAID rebuild, but a full backup is out of my price range. Besides, it's hard to keep backups current and uniformed, especially across multiple HDDs as there is no single 10TB or 15TB HDD. I'm dealing with one file directory so any assortment other than alphabetical is not possible and grouping sections just doesn't seem reasonable to me either. The RAID tower I looked at housed all the HDD and RAID controller and the interface was USB3.0. I can turn it on when I need to access the contents and turn it off when not in use. Surge protector and voltage regulators to attempt to prevent damage from voltage changes and maybe a UPS if needed, question on that later. Computer and RAID tower in the closet, HDMI to TV in bedroom with wireless keyboard/mouse so kids/pets/food no issue. I can go on but everything typical has been checked; only the untypical remains and there is no way to predict those...
Question: Does power failure affect RAID systems more so than your typical HDD?

#1 Why not green HDDs?

#2 A week to rebuild a 10TB? Seems kinda excessive...