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FAQ - Best Practices for RAID Volumes

Always certify a disk before using it

Most modern disks only receive limited testing when they are manufactured. They are tested to ensure that they can start and stop reliably and that they can read and write to some small fraction of the sectors on them. You should not trust your valuable work on these disks until you know that all of the sectors on them can reliably store data. Otherwise, you might write out an important file to a volume on the disk only to discover later than you can't read it back.

You can test all of the sectors on your new disk by using SoftRAID's disk certify function. This will write out data to every sector on the disk and then read it back to ensure that it is reliable. After successfully completing a multi-pass certify on your new disk using SoftRAID, you can be certain that it can store your files and read them back correctly.

Replace a disk when SoftRAID reports disk errors

It is tempting to ignore disk errors when they occur. Your Mac seems to be working fine and yet SoftRAID keeps telling you that one of your disks has an error.

You should take all disk errors seriously. Often a disk which has been reliable will have one or two errors a few months before it fails catastrophically. These disk errors are your early warning sign that a disk is about to fail. For more information on the steps we recommend taking when you encounter a disk with errors, see the disk errors help topic (available under the Help menu when running the SoftRAID application).

Always create mirrors with at least 3 disks

We recommend that your mirror volumes have 3 disks. This allows you to have two disks connected to your Mac at all times, a mirror pair. They can be two internal disks in a Mac Pro, or Mac Mini Server or a pair of external eSATA, FireWire or USB disks. The two disks act as a traditional mirror, if one disk fails while you are working, the second disk takes over and allows you to continue working.

The third disk in your mirror volume should be an external disk which is normally stored in another building. This disk should be connected up to the Mac with the other two disks in the mirror periodically so it can be rebuilt and updated with the most recent volume files. This third disk provides you with a disaster recovery mechanism. If your Mac gets stolen or the building your Mac is in burns down, you will still have the third mirror disk which you can use. At SoftRAID, we rebuild to our third mirror disk every 2 weeks. That way, the most we will ever lose is 2 weeks worth of work.

Set up 2 outgoing email servers for email notification

While we all rely on the internet and the servers on it, they are not available 100% of the time. In our testing we have seen times when email servers are unreachable, even the ones at iCloud, Google and Yahoo. We therefore always recommend that you have two outgoing email servers configured for your outgoing email notification. This will ensure that you always get the email notifications which SoftRAID sends out.

When you configure 2 outgoing email servers, you won't get two emails for every notification from the SoftRAID Monitor. The second (called the “alternate”) outgoing email server is only used if there is an problem sending email with the primary server.

Stop using older disks before they fail

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.

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 once an SSD has less than 10% media life remaining.

We recommend that rotating disks (HDDs) 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.

We recommend that SSDs in laptops be replaced after 20,000 hours of use. SSDs last much longer than HDDs in laptops.

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. 10,000 hours corresponds to 4–5 years of use in an average office environment.

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.