Which RAID Settings Should I Use For My NAS?

RAID 1 (Mirror)

A NAS (Network Attached Storage) puts storage onto your network, where it can be accessed by many computers. They often have more than one hard drive which can allow you to have automated copies of your data, which is known as RAID. A common type of RAID found on NAS devices is RAID 1, which will make two hard drives into a mirror copy of one another. Some manufacturers call RAID 1 Safe mode. If you have a NAS with two 1TB hard drives and set them to RAID 1 mirroring, instead of 2TB of storage (1TB x2) you only get 1TB. Everything you store to the NAS gets saved to both drives automatically. The theory is that if one of the drives fail, you can access all of the data from the other one. In practice that is not always the case. More on that later.

RAID 1 Mirror Animation
RAID 1 Mirror Animation

RAID 0 (Stripe)

Another common NAS option is RAID 0. The “R” in RAID stands for redundant, however there is no redundancy in RAID 0, so it’s not a real RAID type. If you setup the same two 1TB disks as RAID 0, you will get a 2TB volume to store your data on. The problem is that every single file you write to the NAS will be split into tiny pieces and distributed across both drives. If one drive fails, you not only lose the data from that failed drive, but also from the non-failed drive as it only contains half the pieces of each file. RAID 0 should never be used for long term storage, but can be fast so is often used for video editing.

RAID 0 Stripe
RAID 0 Stripe

So that’s the hardware taken care of. What other things should you look out for when choosing a NAS?

Another problem with most NAS devices is the non-standard filesystems they use to store the data on the disks. If the NAS itself fails, you cannot usually read the disks by attaching them to a standard PC. So even in RAID 1 mirror mode, you could end up with no usable copies of your data. Most NAS drives run a simplified version of Linux, but only some of them use standard Linux filesystems like ext2/3/4.

Backup my backup?

Some NAS drives have a USB port to allow you to backup the data to an external hard drive. This is great, as long as you can access the backup data on a regular PC, and it doesn’t need to go through the NAS. You can imagine why that would be a problem.

To summarise, NAS drives can be a great way to upgrade your home or small office storage. They can allow collaboration and sharing of files between users, and should simplify your backup process. Just remember that a NAS is a small server that needs to be backed up as a matter of urgency. As long as you have that covered then a NAS can be a smart addition to your network.

Burning Linux ISO to USB Using a Mac

My main computer is an old MacBook Pro. I often download Linux ISOs to install on other computers. In recent Debian-esque releases this is actually really simple.

1. I find it quicker and easier to install from USB so first insert a USB pen / stick of some sort.

Note: This USB stick will be erased, so don’t use one with data that you need to keep!

2. Next we need to find out which number has been assigned to the USB stick. If you only have one disk in your Mac then the USB will usually be disk1, but always check first. (Note: Disks are numbered from zero, so your internal drive should be disk0) On your Mac open Disk Utility, which is located within Applications / Utilities. (See Image)

Disk Utility
Disk Utility

Select the USB stick from the lefthand window and then click the Info button which is on the toolbar. (See Image)

USB Info
USB Info

You will get a pop up window with loads of information about the device. We only need the Disk Identifier. Make a note of this for later.

Disk Identifier
Disk Identifier

3. To allow us to write data to the USB stick we need to unmount any volumes currently on there. (see image)

Unmount USB
Unmount USB

4. Now comes the actual writing. First locate the Terminal application, again within Applications / Utilities. (see image)

Mac Terminal
Mac Terminal

5. Remember to change the code to match your Disk Identifier from earlier. There are a few things to note about the following command.

  • sudo – allows you to run dangerous commands, so will require an administrator password
  • Instead of typing the location of the ISO file you can just drag the ISO onto the terminal when required.
  • “if” means input file (in this case the ISO file), “of” means output file (the USB stick)
  • When we found out the Disk Identifier, it was disk1. That will work in the command, but we use rdisk1 instead, which gives us raw access to the disk. This may not be necessary, but it works for me.

There is a lot of discussion about block sizes, but I find 4MB is reasonable for writing ISOs to USB. In Linux we often type bs=4M, however the Mac prefers it like bs=4096 instead. It’s the same thing, just expressed differently.

The command:

sudo dd if=[drag iso here] of=/dev/r[disk number] bs=4096; sync

Example:

sudo dd if=/Users/dan/Desktop/linux.iso of=/dev/rdisk1 bs=4096; sync

If you’ve got it right, you shouldn’t get any feedback until it finishes. Your USB stick may have a blinking LED whilst the data is being written. For reference the 200MB debian-netinst ISO took just over a minute to write.

Once complete you should get something like:

48896+0 records in
48896+0 records out
200278016 bytes transferred in 95.151719 secs (2104828 bytes/sec)

This means you’re finished. Now eject the USB and try to boot your PC with it. The Mac may complain that the disk is not readable but just ignore that and try it on a PC.

Debian Boot
Debian Boot

Cheap USB Pen Data Recovery

Cheap USB Pen Data Recovery

Our low cost USB Pen & Camera Flash Media Recovery Services can recover data from physically broken, formatted and deleted USB Pens & Camera cards. 

We have just received an 8GB USB pen with a broken connector. The customer started phoning around and was shocked by the costs he was given. He then called us and was pleased to hear that we only charged £90.00 if the rework was successful. This rework includes dismantling and repair of the USB Pen even when it appeared to be beyond repair.

The recovery was 100% successful.

Bang Goes The Theory Data Recovery

Bang Goes The Theory – Series 6 Episode 3 – March 26th

Bang Goes The Theory Data Recovery

I love Bang Goes The Theory. I loved the alcohol powered motorbikes last week and find it a good doorway into ideas, which are presented in a fun and interesting way. I was extra excited when I started watching episode 3, and relised they would be featuring data recovery. A perfect opportunity to dispel some common myths, and dish out a bit of advice in the process.

Deletion

The data recovery guy Rob, made a good analogy when he described deleting data as ripping out a page from the table of contents. That is pretty much how it works, and really simple to understand.

Data Recovery Experts

Yes they are the world leaders. I’m not going to dispute that, but I’m also not going to name them. They don’t exactly need the extra publicity. It’s worth noting that any decent recovery firm would have reached the same results from the batch of damaged drives.

Getting Physical

I do have a couple of problems with the way some of the drives were “destroyed.”

  1. Sledgehammer. This would have been a good way to destroy a drive, but only if it had been removed from the PC first. Effectively the metal PC case acted like armour, thus protecting the drive from the brunt of the impact.
  2. Tractor. Same as above. If the drive was bare, and on solid ground, then maybe the tractor would have done more damage. Instead, the PC case protected it sufficiently and all the data was recoverable.
  3. Golf Swing. This was great in the example shown, but is a bit unreliable. If you only hit the edge, or if the disk didn’t have glass platters then it may have been recoverable. Maybe take it apart first, then you can see if it’s damaged.
  4. Tea Damaged USB Pen. This was a good one. Solid state storage should survive liquid damage, as long as it is powered off at the time. When dried out, there is a good chance of getting the data back. The worst thing you could do is plug in a wet drive, as this would cause an electrical short, and potentially damage the electronics of the device, and even the computer you plugged it into.
  5. Big Magnet. This was a good one, and surprisingly effective. Only problems are the fact that most people don’t have a giant magnet, and unless you test it afterwards, you wouldn’t know if it had worked.
  6. Toaster. This is an interesting one for me. Of course the toaster damaged the PCB (circuit board) of this hard drive. These drives were quite old, so that was no major problem. If however these were more modern drives the story could have been quite different. A lot of newer drives encrypt the data using keys stored on the PCB. If you melt that PCB, then you have a very difficult job on your hands.
  7. Torched. 100% successful. If you can see the drive destroyed, then that’s perfect.

Optical Discs

Liz later made some good points about the reliability of CD / DVD storage. I agree that although the quoted life spans of DVDs are enormous, in reality DVDs often only last for a couple of years. We have had discs in for recovery that have been stored in temperature-controlled server rooms that have still failed well short of their estimated lifespans.

Hard Disks

Hard disks can last for ages. We have some here that are well over 15 years old and still going strong. The problem is that they can fail without any warning. It is sound advice to backup one drive with another, and then another. This is the only surefire way to avoid being stung by a failed drive. Dallas made a good point of moving one of the backups off site, which is also a good idea.

Scrambling Software

I didn’t like the scrambling advice given near the end. There are problems with the way hard drives are designed, which can prevent the software from accessing bad sectors, and hidden parts of the disk. Although only small parts of the disk, you could leave enough data there to be targeted by fraudsters or whoever.

I advise a two pronged approach. First erase / scramble the data, then physically destroy the drive. This makes it far less likely that your data could end up in the wrong hands.

Summary

It is good to see this sort of thing on mainstream TV, and the advice given was a good starting point for most people. Despite my points above, it was basically a good show: Interesting and informative, with a decent amount of good info.

Many people have little or no knowledge of the way their data is stored, so any way to bring this to their attention is good in my books.

Bigger Hard Drives of the Future

The Register has today posted two articles about the ongoing battle to expand hard drive capacities.

First is an actual device for sale, a 2TB Western Digital portable drive. This drive has a fancy new case and USB3 connection. It contains backup software and also the option to encrypt the data with a password. I wonder if it encrypts the data by default like some of their previous portables. (A bad thing!)

Second is a futuristic announcement from Seagate about their new HAMR technology. This new tech uses a laser to heat part of the disk before magnetising it. This apparently allows for much higher densities, theoretically paving the way for 60TB hard drives. There doesn’t appear to be any products using this technology at the moment.

60TB drives will be fantastic for backups, but horrible to backup without a new, faster form of connection. These would take almost forever (exaggeration) to fill up by SATA.

This news helps prove that hard drives are far from dead. It will take a long time until SSDs can cope with such massive capacities, at a similar cost to these beasts.

USB Powered Portable Hard Drives Failing To Spin

We see a lot of portable hard drives that don’t spin up when plugged into a USB port. All brands of hard drive can be effected including Hitachi, Western Digital and Seagate. The problem can be caused by power loss or sometimes due to mis-plugging of the USB lead. This causes the internal read heads to sit on the disc instead of parking on the ramp at the side.

The only way to overcome this problem is by taking the hard drive into our clean room to replace the damaged heads with good ones. This allows us to copy the data from the drive and store it on our server.

The repaired hard drives are not suitable to be reused after this sort of work as they will not work correctly, or fail after a very short time.