• Year 0 – I filled 10 32-GB Kingston flash drives with random data.
• Year 1 – Tested drive 1, zero bit rot. Re-wrote drive 1 with the same data.
• Year 2 – Tested drive 2, zero bit rot. Re-tested drive 1, zero bit rot. Re-wrote drives 1-2 with the same data.
• Year 3 – Tested drive 3, zero bit rot. Re-tested drives 1-2, zero bit rot. Re-wrote drives 1-3 with the same data.
• Year 4 – Tested drive 4, zero bit rot. Re-tested drives 1-3, zero bit rot. Re-wrote drives 1-4 with the same data.

Will report back in 2 more years when I test the fifth. Since flash drives are likely to last more than 10 years, the plan has never been “test one new one each year”.

The years where I’ll first touch a new drive (assuming no errors) are: 1, 2, 3, 4, 6, 8, 11, 15, 20, 27

The full test plan:

YEAR 1: read+write  1                           [1s]
YEAR 2: read+write  1, 2                        [1s]
YEAR 3: read+write  1, 2, 3                     [1s]
YEAR 4: read+write  1, 2, 3, 4                  [2s] (every 2nd year)
year 5: read+write  1, 2, 3,
YEAR 6: read+write  1, 2, 3, 4  5               [2s]
year 7: read+write  1, 2, 3,
YEAR 8: read+write  1, 2, 3, 4, 5, 6            [2s]
year 9: read+write  1, 2, 3,
year 10: read+write 1, 2, 3, 4, 5, 6
YEAR 11: read+write 1, 2, 3,         7          [4s]
year 12: read+write 1, 2, 3, 4, 5, 6
year 13: read+write 1, 2, 3
year 14: read+write 1, 2, 3, 4, 5, 6
YEAR 15: read+write 1, 2, 3,         7, 8       [4s]
year 16: read+write 1, 2, 3, 4, 5, 6
year 17: read+write 1, 2, 3
year 18: read+write 1, 2, 3, 4, 5, 6
year 19: read+write 1, 2, 3,         7, 8
YEAR 20: read+write 1, 2, 3, 4, 5, 6       9    [8s]
year 21: read+write 1, 2, 3
year 22: read+write 1, 2, 3, 4, 5, 6
read 23: read+write 1, 2, 3          7, 8
year 24: read+write 1, 2, 3, 4, 5, 6
year 25: read+write 1, 2, 3
year 26: read+write 1, 2, 3, 4, 5, 6
YEAR 27: read+write 1, 2, 3          7, 8,   10 [8s]
year 28: read+write 1, 2, 3, 4, 5, 6       9
year 29+: repeat years 21-28

FAQ: https://blog.za3k.com/usb-flash-longevity-testing-year-2/

I’ve been working on a spell guide for D&D games. During the process, I researched the differences between the Dungeons and Dragons 5e Player’s Handbook (PHB) and the 5e System Reference Document (SRD).

For those that don’t know, in 3e Wizards of the Coast released the core rules of the game for free. They’ve continued to do so for 3.5, 4, and 5e. The 5e rules were released under Creative Commons recently (thanks!), in response to some community backlash over proposed licensing changes (eek!).

There are 361 spells in the PHB, but only 318 in the SRD. Which are missing?

Here are the 43 spells in the PHB but not the SRD:

• arcane gate
• armor of agathys
• arms of hadar
• aura of life
• aura of purity
• aura of vitality
• banishing smite
• beast sense
• blade ward
• blinding smite
• chromatic orb
• circle of power
• cloud of daggers
• compelled duel
• conjure barrage
• conjure volley
• cordon of arrows
• crown of madness
• crusader’s mantle
• destructive wave
• dissonant whispers
• elemental weapon
• ensnaring strike
• feign death
• friends
• grasping vine
• hail of thorns
• hex
• hunger of hadar
• lightning arrow
• phantasmal force
• power word heal
• prayer of healing
• ray of sickness
• searing smite
• staggering smite
• swift quiver
• telepathy
• thorn whip
• thunderous smite
• tsunami
• witch bolt
• wrathful smite

Why are they missing? Well, the official WoTC answer is:

In general, the criteria for what went into the SRD is if it (1) was in the 3E SRD, (2) has an equivalent in 5th edition D&D, and (3) is vital to how a class, magic item, or monster works. For example, the 3E SRD has the delay poison spell, but in 5th edition that’s handled by the protection from poison spell, so protection from poison is in the SRD.

Wizards of the Coast, SRD5.1 FAQ

Looking at the actual list, every single spell missing was (1) not in the 3E SRD, (2) was added in 5E. I was curious what fraction of new 5E spells got added to the SRD vs. not, but it looks like no one has a list of new 5E spells, so I couldn’t easily check.

The following are renamed but present in the SRD, presumably for trademark reasons:

• drawmij’s instant summons, evard’s black tentacles, leomund’s secret chest, melf’s acid arrow, mordenkainen’s faithful hound, mordenkainen’s magnificent mansion, mordenkainen’s private sanctum, otiluke’s freezing sphere, otiluke’s resilient sphere, otto’s irresistible dance, rary’s telepathic bond, tasha’s hideous laughter, and tenser’s floating disk are all shortened. They become instant summons, black tentacles, secret chest, acid arrow, faithful hound, magnificent mansion, private sanctum, freezing sphere, resilient sphere, irresistable dance, telepathic bond, and floating disk.
• bigby’s hand becomes arcane hand
• mordenkainen’s sword becomes arcane sword
• nystul’s magic aura becomes arcanist’s magic aura

I did a survey of the cost of buying hard drives (of all sorts), microsd/sd, USB sticks, CDs, DVDs, Blu-rays, and tape media (for tape drives).

I excluded used/refurbished options. Multi-packs (5 USB sticks) were excluded, except for optical media like CD-ROMs. Seagate drives were excluded because Seagate has a poor reputation.

Here are the 2023-01 results: https://za3k.com/archive/storage-2023-01.sc.txt

2022-07: https://za3k.com/archive/storage-2022-07.sc.txt
2020-01: https://za3k.com/archive/storage-2020-01.sc.txt
2019-07: https://za3k.com/archive/storage-2019-07.sc.txt
2018-10: https://za3k.com/archive/storage-2018-10.sc.txt
2018-06: https://za3k.com/archive/storage-2017-06.sc.txt
2018-01: https://za3k.com/archive/storage-2017-01.sc.txt

Per TB, the options are (from cheapest to most expensive):

• Tape media (LTO-8) at $4.52/TB, but I recommend against it. A tape drive is about $1,600 (twice that new). That’s a breakeven at 150-300TB. Also, the world is down to one tape drive manufacturer, so you may end up screwed in the future.
• 3.5″ internal spinning hard drives, at $15.00/TB. Currently the best option is 8TB drives.
• Optical media, at $16.71/TB. 25GB blu-ray disks are cheapest.
• 3.5″ external hard drives, at $17.75/TB. Currently the best option is 18TB drives.

• 2.5″ portable spinning hard drives, at $22.00/TB. Currently the best option is 5TB drives.

• SSD drives, at $42-$46/TB. Best option is 1TB.

• USB sticks, at $59/TB. Best option is 128GB sticks.
• MicroSD cards, at $62/TB. Best option is 512GB cards.

Changes since the last survey (4 months ago):

• Amazon’s search improved. Less refurbished drives and sponsored listings.
• Spinning drives: 22TB 3.5″ drives became available
• Spinning drives: Prices for the previous cheapest option (4TB) rose, making 8TB the new cheap option.
• SSDs: Prices dropped by about 30%.
• MicroSD/SD: Prices dropped slightly.
• Optical: The cheapest option (25GB blu-ray) dropped 30%.
• Optical: I stopped gathering data on the cost of BR-RE
• Tape: LTO-7 tape drives are now available used, halving the break-even point on tape.

• Year 0 – I filled 10 32-GB Kingston flash drives with random data.
• Year 1 – Tested drive 1, zero bit rot. Re-wrote drive 1 with the same data.
• Year 2 – Tested drive 2, zero bit rot. Re-tested drive 1, zero bit rot. Re-wrote drives 1-2 with the same data.
• Year 3 – Tested drive 3, zero bit rot. Re-tested drives 1-2, zero bit rot. Re-wrote drives 1-3 with the same data.

This year they were stored in a box on my shelf.

Will report back in 1 more year when I test the fourth 🙂

• FAQ
• Reddit

Year 0 – I filled 10 32-GB Kingston flash drives with random data.
Year 1 – Tested drive 1, zero bit rot. Re-wrote the drive with the same data.
Year 2 – Re-tested drive 1, zero bit rot. Tested drive 2, zero bit rot. Re-wrote both with the same data.

They have been stored in a box on my shelf, with a 1-month period in a moving van (probably below freezing) this year.

Will report back in 1 more year when I test the third 🙂

FAQs:

• Q: Why didn’t you test more kinds of drives?
  A: Because I don’t have unlimited energy, time and money :). I encourage you to!
• Q: You know you powered the drive by reading it, right?
  A: Yes, that’s why I wrote 10 drives to begin with. We want to see how something works if left unpowered for 1 year, 2 years, etc.
• Q: What drive model is this?
  A: The drive tested was “Kingston Digital DataTraveler SE9 32GB USB 2.0 Flash Drive (DTSE9H/32GBZ)” from Amazon, model DTSE9H/32GBZ, barcode 740617206432, WO# 8463411X001, ID 2364, bl 1933, serial id 206432TWUS008463411X001005. It was not used for anything previously–I bought it just for this test.
• Q: Which flash type is this model?
  A: We don’t know. If you do know, please tell me.
• Q: What data are you testing with?
  A: (Repeatable) randomly generated bits
• Q: What filesystem are you using? / Doesn’t the filesystem do error correction?
  A: I’m writing data directly to the drive using Linux’s block devices.

I was looking into building a raspberry pi based supercomputer lately. Here’s the background research I did comparing pi models. Most of this information is sourced from raspberrypi.org. I was especially interested in which boot methods worked for which models, which is very scattered, as well as prices.