Most modern disks only get limited testing during the manufacturing process. They get tested to ensure that they can read and write data correctly, spin at the correct speed and can start and stop. They are not tested to ensure that every sector can read and write correctly.
You can perform this advanced level of testing on your new disk using the SoftRAID disk certify feature. This will write a pattern to each sector on your new disk and then read it back to ensure that the pattern is identical. Testing your new disks before you use them will prevent you from using a disk which is unreliable which might result in you losing valuable files.
You can also certify a used disk before you reuse it in a different Mac or for a different volume. Certifying a disk will allow you to make sure the disk is working reliably. Remember that certifying a disk will destroy all files and data on it.
You can use SoftRAID to certify a SDHC card before using it in your digital camera. This will ensure that the card is working reliably and that all sectors on it can read and write without errors. If you routinely certify your SDHC cards, you will greatly reduce the chance that you will lose photographs due to media failure. (In a professional photography studio, we recommend that you certify each card every 30–60 days.) Remember that certifying a card will destroy all photos on it.
If you have ever had to recover a file that you've accidentally erased, you know that it's much easier to locate the files you need if all the unused space on the disk is filled with zeros. Even if you've never done this yourself, and have sent a failed disk to a data recovery service, you can imagine that looking for blocks of existing data will be easier if they are surrounded by zeros—it's like highlighting text in a page so it stands out; the zeros are like the un-highlighted text.
SoftRAID helps makes it easier to recover files by filling disks with zeros during the last pass of certifying a disk.
Some of the controllers used on SSDs (Solid State Disks) use data compression to minimize the amount of data they have to write to flash memory. This allows them to minimize the wear on the flash memory and to attain much higher write performance when tested using benchmarking applications. (Most benchmark applications write blocks of zeros when testing the write speed of a disk).
The disk certify function in SoftRAID was written with these data compression SSD controllers in mind. Every pass of the disk certify function, except the last one, will write out a non-compressible random data pattern. This ensures that SoftRAID tests as many of the locations in the memory chips as possible.
If most of the disks you are certifying are getting errors, there are two possible explanations:
You have an unreliable batch of disks. Some manufacturers ship new hard drive technology before it is truly reliable. We have found this to be the case with early shipments of 6 and 8 TB disks. We have also seen this occasionally with refurbished disks.
Your Mac has a hardware problem. Some of our users have more than 50% of their disks fail certification. We have found that this is most often caused by bad or mismatched RAM or other hardware errors. You can test whether a Mac hardware problem is causing your disks to fail by moving your disks to a different Mac and re-certifying them. If they all certify successfully, the most likely explanation is that the original Mac has a hardware problem.
You can further diagnose this problem by removing all 3rd party RAM from the failing Mac or running the Apple memory test.
Every time you start up the SoftRAID application, it gets the SMART status* of every disk which support SMART. In addition, the SoftRAID Monitor gets the SMART status every time you restart your Mac and every 24 hours after that. Each time SoftRAID gets the SMART status of a disk, it checks to see if the disk has failed the SMART test. In addition, the SMART measurements are also used to predict whether the disk is more likely to fail. This prediction is based on results of a study by Google engineers of disk failure using 100,000 disks over an 8 month period.
*SMART is a monitoring system in disk drives that SoftRAID Monitor uses to assess drive reliability and anticipate drive failures.
SoftRAID uses SMART to ask a disk how many hours it has been used. Disks which support SMART are on Thunderbolt, SATA, SAS and Fibre Channel buses. Disks which don't support SMART will say "SMART status: test unavailable" in the expanded part of the disk tile in the SoftRAID application main window.
For disks which don't support SMART, the SoftRAID driver maintains an hours of use counter which it updates every time your Mac is shutdown or volumes on the disk are unmounted. This counter is stored on the disk itself and is still valid if you move the disk to a different Mac. SoftRAID will even restore this counter to its correct value if you initialize the disk a second time.
We recommend that you replace older disk drives even if they have not failed. As disks age, the chance that they will fail increases. It is always better to replace a disk before it fails than to wait for it to fail and have to restore data from a backup or replace a disk on a Mac which is currently in use.
SSDs: most SSDs (Solid State Disks) contain wear indicators which show how much longer they can be used. These count down from 100% of media life remaining down to 0%. An SSD should be replaced once its media life remaining is less than 10%. The media life remaining for a particular SSD is shown in the disk tile in the SoftRAID application. The SoftRAID Monitor will also warn you if any SSD has less than 10% media life remaining. This feature is not supported by SSDs shipped by Apple.
Laptop disks: we recommend that disks in laptops be replaced after 5,000 hours of use. These disks are smaller and less reliable than the disks found in desktop computers and servers. This amount of use corresponds to 2–3 years of use by an average user.
Disks in desktop computers: we recommend that disks in desktop computers be replaced after 10,000 hours. While these disks are more reliable than the smaller ones in laptops, they are subjected to the repeated stress of being turned on and off. This number of hours corresponds to 4–5 years of use in an average office environment.
Disks in servers: we recommend that disks in servers be replaced after 20,000–25,000 hours. These disks are usually properly cooled and are not subject to the stress of being turned on and off but they often experience periods of intense activity. This number of hours corresponds to 2–3 years of use in a server which is on 24 hours a day. These recommendations are corroborated by the Google study on disk failure in servers which showed that disks fail at a rate of 2–3% during the first year and 7–10% during the subsequent years.
If you have many identical external disks, it is often easy to confuse one with another unless you add some sort of label to the outside of the disk. SoftRAID allows you to add the a label to each SoftRAID disk, a label which will appear in the SoftRAID user interface, log entries and email notifications. If the label you add to a disk in the SoftRAID is the same as the label you place on the outside of the physical disk, you can easily keep track of which physical disk corresponds to the one you have selected when you are using the SoftRAID application. This will help prevent you from inadvertently initializing the wrong disk or disconnecting it from your Mac when it is still in use.