I was frequenting Spiceworks earlier today and came across a post asking if “tape was legacy”. I think what they were asking is whether backup to tape is the kind of legacy technology today that we see with VHS—there are still a few out there but the technology is on its way out. I realize that there are still advantages with tape when it comes to large volume backups and the ability to physically move the backup media to an offsite location. But even with these advantages it seems that backups to disk (and dare I say to the cloud?) have so many more advantages.
Let’s do a quick comparison of tape and disk storage to consider the advantages of each:
“As of 2011, the highest capacity tape cartridges (T10000C) can store 5 TB of uncompressed data” (source Wikipedia), while hard drives have followed Kryder’s law (much like Moore’s law) and doubled areal density every two to four years putting disk drive capacity currently somewhere around 4 TB. This capacity is comparable to that of tapes. In addition, newer SSD will have even more capacity than existing disk drives while at the same time offering storage in a smaller and smaller physical size. Add to this the fact that SSD drives are without the moving parts and power requirements of existing drives and it seems that disk storage will far surpass the capacity benefits of tape storage in the near future.
Several tape drives I’ve looked at have write speeds approaching 500 MB/s with LTO-5 claiming speeds of 800 MB/s. The maximum speed of a tape drive depends of course on the limitations imposed by physics on the moving parts and magnetic ribbon. The same limitations also apply to the spindles and platens of a typical hard disk as they rotate inside the disk enclosure. A typical 7200 rpm hard drive might have write speeds around 130 MB/s. However, if we again consider SSD disk drives the typical sequential write speeds are closer to 280 MB/s. These speeds may not be at the same level as tape; however consider the fact that SSD is a newer technology and speeds are constantly increasing. Add to this the important point that a tape read/write is a linear process requiring the tape to move to a specific point before data can be written or read while disks allow for immediate read/write functionality and it seems again that hard disks are the long-term winner.
Call me frugal, but cost is often the most important part of any purchase in my opinion. All else considered equal, I will purchase the lower cost item every time. And this is where I think hard disk drives really shine. Tape storage requires a physical tape drive which can range anywhere from $1,400 to well over $12,000. The tapes themselves range anywhere from $30 to $90 per tape and these costs add up over time. Compare this with a 6TB WD drive for $329 on NewEgg and cost pretty much cinches the deal.
Ok, so there you have it. Three very brief (sometimes read as “not thoroughly researched” or “highly opinionated”) feature comparisons and I think we can say that backup to disk is the clear winner if not today than in the very near future. There’s a reason for the industry moving away from tape backups and towards disk backups. All I have left to say is that I hope you found this brief journey down a rabbit hole to be as fun and informative as it was for me to write it.