07 - Network storage and data redundancy

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NAS servers

In many work environments, many people need to work on the same files. In this scenario, thumb drives or portable disks are not really useful since they would need to change hands all the time. The most useful approach is to enable NAS servers (Network Attached Storage) and allow users to connect to the same files at once.

Workstations (desktop PCs) connect to the NAS server
Workstations (desktop PCs) connect to the NAS server

SMB is the most used protocol for network file sharing. There are other protocols such as FTP and Webdav. SMB does not require any additional software on the client side since it is integrated in all file explorers.

NAS systems usually rely on some kind of redundancy to prevent data loss. There is not just one hard disk drive in a NAS, but an array of drives that have the data cloned in case of disk failure.

Array = conjunto

The RAID system

RAID (Redundant Array of Independent Disks) is a system that duplicates your information in several disks so as not to lose data in the event of disk failure …WHEN disks fail.

RAID is usually created using just software. You could make a RAID in your desktop PC, but that would be a bit overkill. Instead, move your important files to a NAS server regularly (I do it every year) and implement data redundancy (with RAID) in the server.

These are the most used RAID types:

up to = hasta

Check out this RAID calculator.

NAS with 4x 2TB disks. Comparison RAID 1 vs. RAID 5
NAS with 4x 2TB disks. Comparison RAID 1 vs. RAID 5

Never buy many hard disks from the same brand at the same time. Since they come from the same batch, their lifespan will be similar, so you risk them dying at the same time.

What kind of drives should you buy

We have studied three types of storage drives:

Usually NAS are made with many hard disks. There are some NAS made with full SSD, but those are really expensive. SSD cache provides a good balance between cost and speed.

SSD Cache is a combination of many HDDs and one or two SSDs. The NAS intelligently moves “hot” data (the data that is used most) to the SSD for fast reading. When new data is written, it initially enters the SSD and is then moved to the HDD when the NAS is idle.

How many backups are enough

Rule 3-2-1: To be safe, all your data should be stored in three places, on at least two different media (HDD + cloud, for example), and one of the copies should be off-site (in a different location).

You don’t need a NAS server

Any computer can be an SMB server, you just have to install SAMBA. Tutorial.

Test

  1. If you have 3x 2TB drives in RAID-1, you:

    a. …can lose up to two disks

    b. …have 4TB of usable storage

    c. …can lose up to one disk without losing any data

  2. If you have 6x 2TB drives in RAID-5, you:

    a. …have 12 TB of usable storage

    b. …can lose up to two disks without losing any data.

    c. …can lose up to one disk without losing any data.

  3. If all your disks are the same age, you won’t have any risks when replacing a dead disks since the others will be young and healthy. (T/F)
  4. A Raspberry Pi is a cheap computer with an SD card. With SAMBA, you could set up a Raspberry as a cheap NAS server (T/F)

Listening - repairing degraded RAID

Oh sh*t…

One of the disks is dead! It’s time to buy a new disk and swap the dead one for the new one. ASAP.

Working, working, working… what? What is that noise? I don’t like that beeping. It is my NAS. And that is an alarm. OK, this LED is steady while the others are ___________ (1). I don’t like it. Let me check in the software.

OK so the configuration says that one or more SSDs are degraded. So I have four, and one of them ___________ (2) to be disconnected. So I’m going to unplug it and then replace it with another one. I’m going to the back, I’m ___________ (3) the disk. I’m not sure but I believe it’s this. It is ___________ (4) but I don’t see any(thing) abnormal. OK and I have right about here a replacement drive. It is a similar sized drive, but different technology. This is a hard disk, you can see the disk, and this is an SSD. This will run much cooler, and I expect it to live quite a long time.

That’s it. Screws are set and the disk is in the ___________ (5). So back to the NAS. Here it comes… and back to the software. Volume degraded still. So press “storage pool”, “action” and “repair” should be available… OK now it is! Repair! This is the new drive. I’m going to mark it. It is an SSD, OK. Drive ___________ (6) is ___________ (7) 4TB. OK this drive is not listed in the “Synology Products compatibility list”. I don’t ___________ (8). All the data on the newly added drive will be erased. OK. I do want to continue.

And “Apply”. OK now it should be ready in some minutes, but this is quite a stressful time. You can hear that the alarm is now off and it is repairing the RAID. This is very stressful because all the data in these three volumes is being ___________ (9) to the new disk. So, if any of these disks is old and about to be degraded, I could lose some data because RAID 5 requires that all disks are alive or all but one but if a second disks dies in the process well, my data will be gone forever.

Phew
Phew

Questions:

  1. What technology is the new disk?
  2. Are SSDs cooler than hard disks?
  3. Why is replacing a dead disk so dangerous?
  4. According to the following images, should I press “Repair” before the faulty drives are replaced?

Writing - Convince your boss

You have been working for several weeks in an IT enterprise. Your boss has heard you talk about NAS servers and he wants to try buying them for office use. Choose them components for a NAS build. Then write an e-mail for your boss explaining your choice and send it to Daniel.

Synology and QNAP are two of the most popular NAS brands.




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