3 ms·

In other words, a tape drive RAID. But since you can use related techniques to improve performance with hard drives, I don't think that will make up much ground

In other words, a tape drive RAID. But since you can use related techniques to improve performance with hard drives, I don't think that will make up much ground for tape drives.

bduerst 14y ago
Yes, but the point was to get read time with tapes up to that of HDDs.
- mistercow 14y ago
  Which a RAID style system probably won't achieve. HDDs start ahead of tape drives in performance. So it's reasonable to assume that HDD + RAID is also going to perform better than tape drive + RAID.
  - bduerst 14y ago
    They weren't comparing RAID tapes against RAID HDDs, just RAID Tapes against normal HDD
    - jdbernard 14y ago
      No, the discussion was whether they would replace HDDs. From the initial comment: > It's fascinating that tape drives are making a comeback, but to suggest that they can replace HDDs is just a fantasy Tape + RAID vs. HDD with no optimizations is a useless comparison. Why would anyone even care about that?
      - bduerst 14y ago
        Because brudgers talking about speed, specifically?
        mistercow 14y ago
        But it still doesn't make sense to compare HDDs without optimization to tape drives with optimization. Data centers are going to use every affordable optimization at their disposal, so if we want to know "will tape drives be competitive against HDDs" we can't handicap HDDs by comparing mirrored arrays of tape drives to straight, un-optimized HDDs. With that said, I outlined in another comment[1] why a mirrored array of tapes would have pretty huge drawbacks regardless. Even if you have an expensive array of tape drives (as opposed to one drive with many tapes), a mirrored array will drag your write seek performance toward a constant worst case as the array grows. The same is true of RAID 1 for HDDs, of course, but the worst case seek time of an HDD is orders of magnitude less than that of a tape drive, so HDDs still win. In any case, if you look at the details of the situation, the answer you come to is pretty boring: tape drives can compete with HDDs in a small slice of real world cases (often when used in conjunction with HDDs), and higher density tape drives will slightly widen that slice. If you have a situation where you are writing a ton of data, but almost never reading or erasing, then high density tapes will play well to that situation (sans mirroring). If you have a situation where you are writing a relatively small amount of data over a long period of time, reading it back comparatively frequently, and never erasing anything so that your total storage needs become very large, then maybe a mirrored array of tape drives would make sense, if it were behind a sizable HDD array. But it's a stretch. [1]http://news.ycombinator.com/item?id=4690877 http://news.ycombinator.com/item?id=4690877
- brudgers 14y ago
  I'm not sure whose point that was. As is typical, the point is to get tape performance to the point where it is an alternative to HDD. As the article mentions, power consumption may be a viable consideration and at some point it may offset an idealized version of access speed. When the data set is so large that maintaining it all online at once is impractical and the nature of the data makes continuous and immediate access unnecessary, then tape may solve the problem.
brudgers 14y ago
There are two separate goals: improving the speed with which data may be accessed on a tape and improving that speed to the point where it will compete with hard disk drives - or to drive home how important it is to keep these goals distinct, solid state drives. I'm not saying that future tape technologies will be as fast as the hard drives of the equivalent future - linear access has inherent limitations. However, there are relatively simple ways in which data access could be improved and such improvements (and some tuning) could make tape adequate for some applications.

In other words, a tape drive RAID. But since you can use related techniques to improve performance with hard drives, I don't think that will make up much ground for tape drives.

bduerst 14y ago

Yes, but the point was to get read time with tapes up to that of HDDs.

mistercow 14y ago
Which a RAID style system probably won't achieve. HDDs start ahead of tape drives in performance. So it's reasonable to assume that HDD + RAID is also going to perform better than tape drive + RAID.
- bduerst 14y ago
  They weren't comparing RAID tapes against RAID HDDs, just RAID Tapes against normal HDD
  - jdbernard 14y ago
    No, the discussion was whether they would replace HDDs. From the initial comment: > It's fascinating that tape drives are making a comeback, but to suggest that they can replace HDDs is just a fantasy Tape + RAID vs. HDD with no optimizations is a useless comparison. Why would anyone even care about that?
    - bduerst 14y ago
      Because brudgers talking about speed, specifically?
      - mistercow 14y ago
        But it still doesn't make sense to compare HDDs without optimization to tape drives with optimization. Data centers are going to use every affordable optimization at their disposal, so if we want to know "will tape drives be competitive against HDDs" we can't handicap HDDs by comparing mirrored arrays of tape drives to straight, un-optimized HDDs. With that said, I outlined in another comment[1] why a mirrored array of tapes would have pretty huge drawbacks regardless. Even if you have an expensive array of tape drives (as opposed to one drive with many tapes), a mirrored array will drag your write seek performance toward a constant worst case as the array grows. The same is true of RAID 1 for HDDs, of course, but the worst case seek time of an HDD is orders of magnitude less than that of a tape drive, so HDDs still win. In any case, if you look at the details of the situation, the answer you come to is pretty boring: tape drives can compete with HDDs in a small slice of real world cases (often when used in conjunction with HDDs), and higher density tape drives will slightly widen that slice. If you have a situation where you are writing a ton of data, but almost never reading or erasing, then high density tapes will play well to that situation (sans mirroring). If you have a situation where you are writing a relatively small amount of data over a long period of time, reading it back comparatively frequently, and never erasing anything so that your total storage needs become very large, then maybe a mirrored array of tape drives would make sense, if it were behind a sizable HDD array. But it's a stretch. [1]http://news.ycombinator.com/item?id=4690877 http://news.ycombinator.com/item?id=4690877
brudgers 14y ago
I'm not sure whose point that was. As is typical, the point is to get tape performance to the point where it is an alternative to HDD. As the article mentions, power consumption may be a viable consideration and at some point it may offset an idealized version of access speed. When the data set is so large that maintaining it all online at once is impractical and the nature of the data makes continuous and immediate access unnecessary, then tape may solve the problem.

brudgers 14y ago

There are two separate goals: improving the speed with which data may be accessed on a tape and improving that speed to the point where it will compete with hard disk drives - or to drive home how important it is to keep these goals distinct, solid state drives. I'm not saying that future tape technologies will be as fast as the hard drives of the equivalent future - linear access has inherent limitations. However, there are relatively simple ways in which data access could be improved and such improvements (and some tuning) could make tape adequate for some applications.