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Comment by cm2187 | Hacker News Reader

You converge to the mean fairly quickly. Build a NAS of 12 drives and those stats become meaningful.

That being said with 50TB drives just around the corner [1] and SSD caching becoming the norm, 12 bays consumer NAS will become rare.

[1] https://www.anandtech.com/show/18733/seagate-confirms-30tb-h...

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At what point to increased rebuild times mean that the increased redundancy requirements overwhelm the increased capacity? If you're running large parity groups, the redundancy required is rather small, but when you move to smaller raid groups allowing for a second (or third) drive failure significantly impacts total storage.

Agree, but that's what backups are for. RAID5 isn't a backup, it's a way to stay online during the rebuild. If you are using RAID5 but don't backup your files, you probably don't care about those files that much.

If you want <X% chance of having to restore from backups, and rebuild times go up, you'll need to switch from RAID5 to RAID6 in order to maintain that.

RAID or not, if you lose an active drive you will need to 1) restore from backup, 2) fill a new backup drive

If it takes days to fill your new 50 TB backup drive, you have the same problem RAID5 has with rebuild times. The drive might fail in the middle.

RAID isn't a backup mostly because if you overwrite RAID data, you wrote over every copy at once. Non RAID offsite backups don't solve any problem related to drive size, they just make it a lot less likely for a single event to take everything out in the same minute.

Absolutely, you want RAID + backup, not one or the other.

50TB at 200MB/s is about 72h. Doesn't seem to be a particularly problematic rebuild time (and that's assuming 100% filled). Of course you need to do regular data scrubbing. If your rebuild is the first time the data is being read in 5y, that might not go so well.

> 50TB at 200MB/s is about 72h.

Assuming the device is offline for users during that time, otherwise there may be reduced throughput.

Yes, and this can be quite painful.

If you have standby sets (like a read replica of a db that can take over for master, or a DR site), you can switch temporarily.

It’s good to know what throughput you have under load for this reason among others.

Also, you can slow or pause some RAID during peak hours.

But if we are talking about a NAS, hopefully you also have SSD caching which should reduce a lot the workload on your disks.

> RAID or not, if you lose an active drive you will need to 1) restore from backup

RAID 1 joins the chat

> RAID or not, if you lose an active drive you will need to 1) restore from backup

Er what? I've had production machines lose a drive, have it replaced, and never leave production. Why would you need to restore from backups?

Right, that was said very poorly. What I really wanted to express was that you need to fill a new drive either way, either by resilver or by making a new backup. Point one is bad, not sure why I wrote that!

Why do you think that 50TB drives will make 12 bay NAS become rare?

We'll just hoard bigger files, like thus far.

My iPhone shoots 90 megabyte photos.

Thats is quite poor compression. My 26 mpix Fujifilm cameras makes ~30 MB compressed RAFs that for sure has better image quality in final output.

The iPhone is 48 megapixels.

Yea, clear demonstration why more pixels ≠ better quality. But ridicolous amount of data.

https://en.wikipedia.org/wiki/Computational_photography

Specifically, the night mode on recent (2y) devices.

I don't know, my own experience is that drive capacity increase exponentially but my storage need are fairly linear, bigger files but not that many more bigger files.

I've noticed that media files seem to look "good enough" at 720p for cartoons and 1080p for live action. I know some people obsess over the highest quality of everything (4k 10bit HDR) but even those came out in 2016[1] and aren't that popular. Higher definition like 8k is basically non existent, it can't run on old HDMI cables and needs both a beefy decoder (Blasting heat) and a powerful display driver as well.

[1] https://en.wikipedia.org/wiki/Ultra_HD_Blu-ray

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