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 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.
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.
Plenty of shops will sell you a “Mac Hard Drive” but there is no reason why you cannot use a windows format drive on a Mac. You just need to format it first. There was once a time when a drive was specially formatted by Apple to use on their Macs, but these days Apple use the same hard drives as everyone else. To use with the latest versions of OS X I would recommend following the steps below.
NOTE: Formatting your drive will destroy all the data. Make sure there’s nothing on there you need.
1. First attach the drive to your Mac. The Mac will notify you with a small finder window to initialise the drive. See below.
2. Once you have clicked initialize you will see the Disk Utility Application window. See below.
3. You need to select the drive you want to format in the left hand window of the utility as highlighted in blue. Internal drives show as grey and external drives show as yellow. At this point make sure you choose the correct drive, the utility will not allow you to format the internal boot drive. See below.
4. Now choose the Partition Tab. See below.
5. Now click on the Partition Layout drop down bar and choose the first option “1 Partition”. Also to the right under Partition Information give your drive a name and below that choose the partition type you want which will be Mac OS Extended ( journaled ). We are nearly there. You now need to click on the options tab in the bottom left of the utility window and choose GUID Partition Table and click okay. As you will read in the text information, this allows the drive to be used with all current OS X Macs. See Below.
7. Now all you need to do is click the apply button as shown in red below.
8. Another window will appear asking for confirmation to partition the drive. Click partition. See below.
9. A formatting window with a progress bar will now appear and then disappear when done. You will now see your named drive in the left window, which means that your drive is now formatted. Close the disk utility and the hard drive is ready to use. See below.
SSDs (Solid State Drives) may one day become the standard form of storage in computers. Apple laptops are already heading that way. There are certainly many advantages when comparing SSDs to HDDs (Hard Disk Drives), however they do bring their own problems, which are often not well reported. We don’t care how good SSDs can be. We care about how they fail. It’s common to hear things like: “I’m replacing my hard drive with an SSD so I won’t have to worry about it crashing again.” While this is technically true – there are no moving parts to crash – there are plenty of other ways an SSD can fail. Whether it’s technically crashed or not doesn’t matter at all when you can’t access your files. It’s a shame but an SSD does not get you out of the boring task of running regular backups.
There are some pros and cons which specifically affect data recovery from SSDs. I haven’t listed things like battery life or read / write speed as they are not relevant when it comes to recovering data from them.
SSD Data Recovery Pros:
Shock resistance. No moving parts to crash.
Just as susceptible to filesystem issues, deletion, reformatting, bad sectors etc which can be recovered using existing equipment.
False sense of security. The word reliable comes up a lot in SSD marketing with phrases like “More reliable, faster, and more durable than traditional magnetic hard drives.” Maybe research exists that shows SSDs are less prone to failure but it doesn’t seem to be the case at the moment. Anything that holds your valuable data runs the risk of getting drenched, getting stolen, getting lost, and that’s before we even take general failures into account.
Susceptible to electronic failure, Maybe more so than a hard drive as the storage and electronics are combined in SSDs. Some of the most common hard drive failures are caused by errors in the firmware which controls the performance of the drive. SSDs have very complex firmware, which opens the possibility of firmware corruption. In most cases firmware corruption will block access to your data.
Encryption. Most modern SSDs encrypt the data at a hardware level, which makes it impossible to remove data chips and extract data from them externally (you can do it, but the data is encrypted). The keys to the encryption are often stored within the controller chip, so if that fails, you could be locked out of your data for good. Modern encryption works well. You can’t get round it.
Wear-levelling algorithms. Which move the data around the SSDs to improve performance, can make recovery difficult as these algorithms would need to be taken into account when accessing a failed SSD. They don’t store data in logical order like hard drives do.
We have been offering Apple Mac Data Migration as a service for many years now. Here’s a quick reminder about this service which we call Mac Setup. You are bound to be over the moon when you are told that we have recovered your lost data, but in many cases this is only half the battle.
We wrote a detailed blog on the subject back in November 2011, but it still appears to trouble many customers.
We still often get the questions: “What do I do with the recovered data once I receive it?” and “How do I get the data back into it’s original places on my Mac?” For out-of-warranty Macs, this is where our Mac Setup comes into play. For a fixed cost we will provide you with a new installed hard drive, with all your recovered data migrated into it’s original locations, so that when you receive your Macintosh computer back, hey presto! it’s as if your Mac had never failed in the first place, everything up and running as it was.
In most computers, when you save files they get stored on a hard drive. Although you wouldn’t know it, the drive does not store your files in a straightforward way. The data is written magnetically by a fixed comb of heads stacked above one another. These heads pass between several magnetic discs, writing data as they go. In most cases, instead of storing files on one whole disk they are split up and spread across the disks. This means that when we carry out data recovery we usually need all of the disc surfaces in good condition to get the data back.
When required we can use a process to take the data from the drive by one disc surface at a time. This can allow us to avoid a failing head until we have the rest of the data extracted. When we have extracted all of the data the parts are combined to allow access the files. In some cases this is the only way to get the data back.
Hard drives do not allow access to individual disks during normal operations so we need to use specialist hardware and software.
We commonly need to access individual heads on Hitachi drives, due to degraded magnetic discs. Also if a drive is dropped when in-use, it will often damage at least one head.
Apple have recently announced a recall program for all iMacs with internal 1TB Seagate Hard Drives. These hard drives fail unexpectedly with no prior warning. We noted the failure of these hard drives in a post back in 2009. You can check whether your iMac has an internal 1TB Seagate Hard Drive by entering your iMac Serial Number at this link.
This recall program has now ended. If you have one of these hard drives that has failed you may be interested in our Mac Data Recovery Services.
October was a pretty busy month for us, so I thought it would be a good chance to check on our success rate. As you can see from the graphic below, we have a great success rate of at least 69%. We always keep an eye on our success rate, to make sure we are still recovering as many drives as possible. Our success rate is often higher than 69% but we did get a few non-recoverable drives which had suffered physical media damage. For an example of why those are unrecoverable, have a look at a photo of a head crash. (Tip: Those dark circular lines are not meant to be there!)
Of those successful jobs, a whopping 90% of them were recovered without even needing to repair them in our cleanroom. This is interesting as cleanroom facilities are often advertised as one of the most important factors when choosing a data recovery company. Not to undermine the need for cleanroom facilities, but they are not required for most hard drives.
In the graphic above we have classified non-cleanroom jobs as external, and cleanroom jobs as internal.
As somebody recovering data from RAID arrays, my view on them is a little different to the norm. In most cases I would say avoid RAID wherever possible. Simplicity is key.
Below are my answers to some real questions I have received from clients about RAIDs.
Why did this RAID disk fail?
Hard drive failure is not unusual and is often not avoidable. The truth is that all hard drives fail eventually, whether they are used in a RAID or not. Even though a RAID system can provide some fault tolerance from physical drive failure, they do have limits. A RAID5 on three disks for example can only handle a single drive failure at any one time. It is common for a second disk to fail whilst the other disk is being replaced. This is when RAID recovery is required; to first access the failed drives, and then rebuild the RAID. The best protection against RAID failure is to make backups. Backups in as many formats, in as many different physical locations as possible.
Why did the server fail so badly? Isn’t RAID meant to prevent this?
A 3-disk RAID5 can only cope with one bad disk. This doesn’t help when two drives fail at the same time. Although a RAID array can provide some leeway when it comes to disk failures, it doesn’t always help when you have multiple failures in quick succession. Adding more disks to the RAID can provide more redundancy, however this costs more money, and also adds complexity when things go wrong. Also you could be in a similar position if three disks happen to fail next time. A live system could fail at any time so prepare for the worst. Backups are cheap, and take a relatively short amount of time. RAID recovery can be expensive and cause unnecessary downtime.
Why couldn’t our IT support recover this?
We are a specialist data recovery company, with access to tools and resources which are not available to IT Support staff. We have spent the last fifteen years perfecting the process of extracting data from failed & failing hard drives and RAID arrays. For the best chance of recovery, we like to get the drives as soon after failure as possible. If more work gets carried out on the drives, things can be made much worse.
How can we avoid this happening again in the future?
To avoid similar problems in the future, the best way forward is some form of regular backup. The backups should be verified and then tested / restored as often as possible. This is where disaster recovery comes in, which can involve simulating certain types of failure and making sure you can get up and running again from your backups. At the very least, it wouldn’t hurt to put the really crucial business files onto an external hard drive every few weeks and store it in your company safe. It’s low-tech but at least you could plug it in to any PC and access the important business data if required as a last resort.
I’m not against RAIDs. They do have their place, but cannot be relied upon as a replacement for regular backups.
This immense 2TB iMac drive may be heavy, but have you ever wondered why?
When we recover these drives we often have to work on individual heads. As you can see from the image, this monster has 10 heads (the first is numbered zero). This means there are 5 spinning disks inside the drive.
From the outside, the only clue that these drives are so rammed full of disks is their weight. They are no bigger physically than any other desktop hard drive.
When you boot up your computer, you expect to see all your familiar files on the desktop, or maybe in the documents folder. What you may not realise is that those folders are actually a bit harder to find if you look at the disk externally. It depends what operating system you use so below is a general guide of locations for Mac & PC users.
Windows Operating System
All user data should be stored within the user profile folder, which is created when the PCs is first used. This is usually located in the following locations depending on the version of Windows:
Windows 95, 98, NT, 2000 & XP
Local Disk C:\Documents and Settings\User ( for example C:\Documents and Settings\John )
C:\Users\User ( For example C:\Users\John )
In systems earlier than Windows 7, some software may be stored in the “Program Files” folder in the root of the drive. This was considered bad practice so in Windows 7 any Program Data should be found in the “Program Data” folder on the root of the drive and not in “Program Files.” Sage Accounts can often be found within the C:\Program Files\Sage\ folder.
Macintosh Operating System
All user data should be stored within the user folder, which is created when the Mac is first used. This is located in the following location:
Macintosh HD/Users/user ( for example Macintosh HD/Users/john )