Data Backup Digest

Although solid state drives offer great speeds over a standard hard disk drive, the problem is that they are too expensive at the moment. This is where the hybrid drive steps in. A few years ago, Seagate and Samsung introduced a drive that paired a small SSD with a mechanical drive. The aim was to achieve the speeds of flash memory while still being able to offer high capacity at a low price. Toshiba and Western digital later followed with their own take on the hybrid drive and now Apple have added their own to the fray.

The hybrid drive uses software caching algorithms to split data between the SSD portion of the drive and the HDD side. The operating system sees the drive as a single device, with the SSD memory being a large cache. However, it is non-volatile and doesn’t vanish when there is no power. This algorithms track which files are loaded the most (usually things like the operating system and program files) and store them on the SSD side. Over time, as the caching improves, so will the speed of the drive.

The hybrid drive boasts quicker boot up times (since the operating system is stored on cache) and also reduced power consumption on the SSD side since it doesn’t need to spin up each time to access certain bits of data. However, there are downsides. The first is that there is longer seek times for data stored on the hard drive, recovering from failed flash memory modules is tricky and the hardware cost can be more than buying two separate drives.

As mentioned earlier, in late 2012 Apple came out with their Fusion Drive that would be in their new iMacs. The drive combines flash and hard drive storage, like a hybrid drive does. However, they are not exactly the same thing. In the hybrid drive the cache storage is not visible to the user, but in the Fusion Drive it is. This means that the drive displays as having 1.12 TB of storage instead of 1 TB (for example). The Fusion Drive uses block based storage instead of file based, which is beneficial for large files that change state regularly and also for coping with the limited storage space of a solid state drive.
The Fusion Drive is more like Automated Tiered Storage. In a standard caching solution, files are stored on the hard disk drive and mirrored temporarily onto the cache as and when needed. In the Fusion Drive, however, the data is moved from one tier to another. The bonus of the Fusion Drive is that all writes are performed on the SSD drive and then moved to the mechanical side if needed. This means that initially there will be faster write speeds. For example, if you are using word processing software often then it will be moved to the flash memory in order to increase access times.
Due to the volatile nature of both of these storages it is essential that you are performing regular backups in order to ensure that your data is safe. Recovering from a damaged flash memory drive can be tricky.