Tape backup vs disk backup

Recently price of inexpensive SATA hard drives is becoming very low while their capacity is growing up. There're many pluses and minuses of both tape- and disk-based backup systems.

Price. Tape backup system is still much less expensive than disk-based backup. Let us show pricing for disk-based and tape-based storages for 14TB:

Disk-based configuration:

Tape-based configuration:

As you can see, pricing of tape-based solution is about 57% of disk-based solution.

Stability.

Average tape cartridge is able to handle approximately 250 cycles. In our situation we use approximately 6 cartridges per week, which is 24 cartridges per month. With 60 cartridges loaded into library, each cartridge is used 2.5 times per month, which is 250 cycles/2.5 per month = 100 months. Of course it depends on your environment condition. For example, if temperature is unstable or you have some dust in your location, it may decrease your tapes' lifetime.

Hard drive-based system looks more stable but as our experience shows, SATA hard lifetime is about 1-2 years, depending on usage, and environment and luck but still if you fail to notice RAID failure on time you have great chance to loose all backup data in case if two hard drives will fail in RAID5 configuration and if three hard drives will fail in RAID6 configuration.

Long term saving.

If you want to keep your data for long time, for example, banks records and any other records that require saving for long time, you can save data on tape cartridges, pull them out and save them at different location for long time. Average safe time is about 30 years. As you understand, this solution is almost unavailable for disk-based storage.

Power consumption.

Dell PowerVault 136-T consumes 110 Watts per hour while disk-based storage with 28 hard drives and single CPU uses about 800-1000 Watts. And due to this fact, to support your disk-based configuration, your cooling system must be able to handle this power consumption as well.

Availability. Because tape-based storage is sequence read-write system, there's only one operation available in a moment. For example, if you need to restore your data, you must stop current backup in order to restore data. And also nobody else is able to restore data at this moment. Disk-based system is free from this limit, which is big advantage if you provide backup system of many customers who need to access to their data simultaneously.

We don't know which solution is the best for you. You need to consider your needs and choose most suitable solution for your situation. Each solution has minuses and pluses. You could try from lower solution (tape-based system) and expand the whole system by disk-based solution. For example, you can use disk-based solution for immediate access to data, while keeping 2-3 months of full backup on your inexpensive tape-based system.