My desire to draft this post was inspired by a recent pic from X, former Twitter.
Storage Pool 2 (Damaged)
My career is over.
I set up RAID 10 for four HHD disks, but two of them became faulty within two hours. They have persisted my code for the past seven or eight years.
Tomorrow, I am going to try some enterprise-level data recovery services. When I saw DAMAGED, my heart stopped.
I bought two WD disks and two Seagate disks from different batches on purpose, but they still crashed simultaneously.
I am using this chance to note down my practices of home data backup and redundancy against what I balance with privacy.
Let me start with this pic above. As a long-term user of NAS, I also encountered a situation where two disks were faulty nearly at the same time. At that moment, I just started to use NAS, so my dependency on NAS was pretty weak. Once I found one of the disks got down, I directly shut NAS down and ordered a new disk. Less than half an hour after I replaced the faulty disk with the newly procured one, another disk got down as well. So, if I had not shut the NAS down previously, I would have faced data loss.
As my dependency on the NAS got stronger, I found that it was tough for me to shut the NAS down when there was a faulty disk. Not to mention that the delivery in Singapore is much slower than in China, and waiting for one week for a new disk is not rare, so I was thinking of how to reduce the concurrence of two faulty disks without shutting the NAS down.
When one disk gets down, besides shutting the NAS down, lowering the disk IO, etc, reducing the concurrence of the failure of the second disk is not an easy thing. So, from my perspective, it is more realistic to reduce the failure duration of the first disk by setting up a standby disk.
How to Reduce the Risk of Double Faulty Disks for NAS: Standby Disk
The NAS I always use is 4-bay, but I only use three of the four disks to create a storage pool with Synology Hybrid RAID (SHR) enabled. The fourth disk is a standby disk instead of part of the storage pool.
When a faulty disk is found in the storage pool, I will immediately replace it with the standby disk and remove it from the NAS.
I will order a new disk. After I receive it, I will install it in the NAS as a standby disk. This will maximize the reduction of the failure duration of the first disk.
But if another disk fails when the newly procured disk is on the way, I will still shut the NAS down as well.
Reduce the failure duration of the first disk by using standby disk
If something happens often enough, it will be inevitable regardless of its low probability.
Anything that can go wrong will go wrong.
Murphy’s Law
Obviously, putting eggs into one basket, NAS, is not reliable; after all, RAID is not data backup but data redundancy. As I mentioned in my previous post, Unconventional Usage of LazyCat MicroServer, I still rely on LazyCat MicroServer to backup some important data, such as photos, as shown in the following figure:
Dual Usage of Synology Photos & LazyCat Photo App
In fact, for such important data as photos, this is still far from enough. After all, the NAS and LazyCat MicroServer are both at home and strictly speaking, this does not count as off-site disaster recovery. So, I also use cloud storage to build an accepted version of 3 data centers in 2 locations 😂.
Accepted Version of “3DC in 2LOC”
I did a bit of simple thinking before confirming the implementation plan:
Family photos, in my opinion, are extremely private data, so I have always hesitated to store them in cloud storage. Considering the limitation of local storage regarding data security, I had to compromise and accept uploading encrypted photos to the cloud. Ultimately, I preferred Syncthing because it supports encrypting the data before syncing.
Cloud storage should offer high guarantees regarding privacy protection, compatibility, and stability, so I ultimately chose Google Drive.
Thus, the plan was confirmed.
Accepted Version of “3DC in 2LOC”
Of course, it is impossible to protect all the data with this implementation. Also, from the perspective of data backup itself, it’s impossible to achieve comprehensive coverage, and cost control also needs to be considered. Please skip the next section for guys who do not care about cost. 😂
Data Classification
Before proceeding with data backup and redundancy, it is necessary to classify the data first.
I classified all the data into four levels:
Level 1: Data should remain regardless of the existence of me
Level 2: Data should remain when I exist
Level 3: Better not lose the data
Level 4: Not important
Additionally, I also classified the data into another three levels based on the privacy requirements:
Level 1: Absolute privacy
Level 2: Not suitable to disclose in the public domain
Level 3: Can be displayed in the public domain
Based on the classification above, a simple scheme matrix has been drafted.
Persistence Level
Privacy Level
Example
Plan
Misc
Level 1
Level 1
Private projects and related data
NAS + LazyCat + Google Drive (Encoded)
Accepted version of “3DC in 2LOC”
Level 2
Non-private contracts, documents, etc.
NAS + LazyCat + Google Drive
Level 3
NA
Level 2
Level 1
NA
Level 2
Non-private contracts, documents, etc.
GitHub Private Repo + Google Drive
Dual cloud
Level 3
Open-source projects and related data
GitHub Public Repo + Google Drive
Dual cloud
Level 3
Level 1
Purchased digital media
NAS + LazyCat
– Dual local storage – Privacy due to copyright
Level 2
NA
Level 3
NA
Level 4
Level 1
Insignificant documents and data scattering across various devices
NA
Level 2
Insignificant documents and data scattering across various devices and clouds
Level 3
Insignificant documents and data scattering across various devices and clouds
Data Classification
The dual-cloud solution mentioned in the table above is too common to be elaborated on. The NAS + LazyCat solution is actually the same as the one mentioned in the post, Unconventional Usage of LazyCat MicroServer. That’s all for now.
Got the budget on my birthday, and the Black Friday deal was not bad, so I finally got a new toy: the reMarkable 2. 😂
reMarkable 2
Before I got this tablet, several guys recommended this to me, and what finally convinced me to buy it was no more than its extreme paper-like writing, thinness, lightness, design, etc. But after I experienced this reMarkable 2, I found its usefulness and customizability were totally beyond my expectation. The most surprising thing is that reMarkable OS is based on Linux and the manufacturer generously exposes the SSH port and root password.
During the year-end holiday, I went through this tablet a lot and would take notes with this post.
Functionality Completeness
Language Issues
The reMarkable 2 does not support non-Latin characters, so CJK (Chinese, Japanese, and Korean) characters are displayed as squares, as below.
Squares
One compromised solution is to use PDF only if possible, but we still need to ensure that all the necessary fonts are embedded in the PDF documents. If any CJK characters apply fonts not embedded in the documents, they will still be displayed as squares.
Luckily, the OS of reMarkable is based on Linux, and the SSH and the root password are available, so we can easily install the CJK fonts. Take this page as a reference for installing the RMPKG.
And the Noto Sans font can support CJK characters now.
Type Diversity
The reMarkable 2 only natively supports PDF and EPUB, but more is needed. Toltec, this community-maintained repository of free software for the reMarkable tablet, helps. With Toltec, we can install KOReader into reMarkable 2. Thanks to the powerful format compatibility, we can read documents in almost all major formats with the reMarkable 2.
## Use opkg to install remux and koreader after installing the Toltec
opkg update
opkg upgrade
# remux# Launcher that supports multi-tasking applications
opkg install remux
# KOReader# Ebook reader supporting PDF, DjVu, EPUB, FB2, and many more formats
opkg install koreaderCode language:Bash(bash)
There is one thing that needs to be highlighted. The shelves of the reMarkable and KOReader do not share; we can surely use cloud storage to solve this. I will share this later. Before installing the Toltec, please ensure that the current Toltec release can support the OS version of your reMarkable tablet.
The Toltec repository includes lots of exciting software. Take your time to go through it if you are interested.
Article Management and Document Management
The reMarkable provides a browser extension. With this extension, users can convert web pages into EPUB documents and put them on the reMarkable’s shelf with one click. It is really convenient, but it is hard for me to get used to it.
The format of the EPUB document content converted by the extension looks strange.
Years of using Pocket as a read-it-later application make me not plan to switch to reMarkable. And I don’t want to put all my saved web pages on the reMarkable’s shelf.
So I started automating pushing the saved pages from Pocket to reMarkable, and I recalled n8n, an open workflow automation platform.
I heard about n8n before, and I tried this time and found it was really convenient. I deployed n8n on the NAS, then created this workflow quickly. You may see that the UI of workflow on n8n is really visual and user-friendly.
Pocket 2 Google Drive
I use a scheduler to trigger the workflow below.
Get the saved timestamp of the last run, and retrieve the pages saved after the last run. The API for retrieving the saved pages has an optional parameter: since. With this parameter, Pocket will only return items modified since the given UNIX timestamp.
If the list is not empty, the workflow will use the OneSimpleAPI to convert the web pages into PDF documents and upload them to Google Drive one by one.
Update the saved timestamp to present.
The above workflow nodes of OneSimpleAPI and Google Drive are natively supported by the n8n and are very easy to call.
These tips may reduce some of the confusion when you are creating a similar workflow:
The since parameter of Pocket API uses the last modified time as a reference. If you would like to push some outdated saved pages to Google Drive, you just need to make a slight change to them, such as tag modification and resaving it again, and these pages will be pushed to Google Drive.
When you trigger a deletion of a saved page, Pocket will update the status of this page to 2 before the page is totally removed. So please ensure all the saves whose status is 2 will be filtered out to prevent unnecessary uploading.
The Google Drive node supports two authentication methods: OAuth 2 and ServiceAccount. OAuth 2 requires that your callback URL contains a domain name other than an IP. For security, my NAS blocks all direct external access and only allows VPN access, so I have not bound my NAS to any domain name. So anyone whose NAS is in the same situation as mine, please prefer ServiceAccount. Primarily the service account is not your Gmail account, so please grant the R/O permission to the Google Drive folder of your reMarkable documents to the service account.
Permissions Granted to Service Account
Actually, I can directly push the documents onto the reMarkable shelf, but I don’t think this is a good idea. The limitation of documents’ count on the reMarkable shelf can help me focus more on the current readings before I pick new readings from Google Drive. I will not let too many documents mess up my reMarkable shelf.
As I mentioned, the shelves of KOReader and reMarkable 2 don’t share, so using Google Drive to store my pending readings can make the shelves tidier. It is also easy for KOReader and reMarkable 2 to retrieve the documents wirelessly.
Publication management
Ages before, I started to use Calibre to manage publications, such as novels, books, comics, papers, etc. Then I moved the library of Calibre to NAS and ran Calibre Web in a Docker container so that I could manage the publications from any device.
Calibre Web is not an official product of Calibre, and there is more than one fork on GitHub. I prefer the image managed by linuxserver.io. If you have never used Calibre before deploying Calibre Web, you will need a new library file (metadata.db) to initiate the configuration. You can install Calibre to create a library or download it from here.
Besides the publication management via web UI, Calibre Web also supports the OPDS catalog.
The Open Publication Distribution System (OPDS) Catalog format is a syndication format for electronic publications based on Atom and HTTP. OPDS Catalogs enable the aggregation, distribution, discovery, and acquisition of electronic publications.
OPDS Catalogs use existing or emergent open standards and conventions, with a priority on simplicity.
OPDS Catalog 1.2
In this way, I can search for publications from the OPDS catalog.
If items exist, the OPDS catalog will send an XML containing publication information, including book names and links, as a response.
<?xml version="1.0" encoding="UTF-8"?><feedxmlns="http://www.w3.org/2005/Atom"xmlns:dc="http://purl.org/dc/terms/"xmlns:dcterms="http://purl.org/dc/terms/"><id>urn:uuid:2853dacf-ed79-42f5-8e8a-a7bb3d1ae6a2</id><updated>2022-12-29T16:23:55+00:00</updated><linkrel="self"href="/opds/search/root cause?"type="application/atom+xml;profile=opds-catalog;type=feed;kind=navigation"/><linkrel="start"href="/opds"type="application/atom+xml;profile=opds-catalog;type=feed;kind=navigation"/><linkrel="up"href="/opds"type="application/atom+xml;profile=opds-catalog;type=feed;kind=navigation"/><linkrel="search"href="/opds/osd"type="application/opensearchdescription+xml"/><linktype="application/atom+xml"rel="search"title="Search"href="/opds/search/{searchTerms}" /><title>Calibre-Web</title><author><name>Calibre-Web</name><uri>https://github.com/janeczku/calibre-web</uri></author><entry><title>Root Cause Analysis Handbook</title><id>urn:uuid:06a66a9a-59d4-415b-a472-a413b8cf923d</id><updated>2022-12-22T07:56:20+00:00</updated><author><name>ABS Consulting</name></author><publisher><name>Rothstein Publishing</name></publisher><dcterms:language>eng</dcterms:language><categoryscheme="http://www.bisg.org/standards/bisac_subject/index.html"term="Business & Economics"label="Business & Economics"/><summary>Are you trying to improve performance, but find that the same problems keep getting in the way? Safety, health, environmental quality, reliability, production, and security are at stake. You need the long-term planning that will keep the same issues from recurring. Root Cause Analysis Handbook: A Guide to Effective Incident Investigation is a powerful tool that gives you a detailed step-by-step process for learning from experience. Reach for this handbook any time you need field-tested advice for investigating, categorizing, reporting and trending, and ultimately eliminating the root causes of incidents. It includes step-by-step instructions, checklists, and forms for performing an analysis and enables users to effectively incorporate the methodology and apply it to a variety of situations. Using the structured techniques in the Root Cause Analysis Handbook, you will: Understand why root causes are important. Identify and define inherent problems. Collect data for problem-solving. Analyze data for root causes. Generate practical recommendations. The third edition of this global classic is the most comprehensive, all-in-one package of book, downloadable resources, color-coded RCA map, and licensed access to online resources currently available for Root Cause Analysis (RCA). Called by users "the best resource on the subject" and "in a league of its own." Based on globally successful, proprietary methodology developed by ABS Consulting, an international firm with 50 years' experience in 35 countries. Root Cause Analysis Handbook is widely used in corporate training programs and college courses all over the world. If you are responsible for quality, reliability, safety, and/or risk management, you'll want this comprehensive and practical resource at your fingertips. The book has also been selected by the American Society for Quality (ASQ) and the Risk and Insurance Society (RIMS) as a "must have" for their members.</summary><linktype="image/jpeg"href="/opds/cover/30"rel="http://opds-spec.org/image"/><linktype="image/jpeg"href="/opds/cover/30"rel="http://opds-spec.org/image/thumbnail"/><linkrel="http://opds-spec.org/acquisition"href="/opds/download/30/pdf/"length="24812876"mtime="2022-12-22T07:56:20+00:00"type="application/pdf"/></entry></feed>Code language:HTML, XML(xml)
Based on this, I created the workflow below to upload the document I need to Google Drive automatically.
Search for the book and upload the needed books to Google Drive.
I use the Webhook node to pass the query string to the OPDS catalog to search for the publications.
Others
There are many functionalities worth going through on reMarkable, such as templates. I am amazed by the completion of reMarkable’s support for PDF, especially the support for the internal links. Many E-ink tablets almost don’t support internal links in PDF documents. Even to support some significant internal links such as tables of contents, they compromise toggle a menu to help users locate the pages instead of jumping during the document reading.
So we can generate templates with reCalendar. This template can help us plan and summarize in a year-month-day dimension. To prevent loading too long, the timespan of the preview below is only two months. You can also tweak the template by adding special dates, modifying the timespan, etc., with reCalendar.
Reload document 
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