[tpm] OT: Are SSDs really worth purchasing to speed up our computing experience?

[Stuart Watt]

On 2012-05-30, at 11:53 PM, Antonio Sun wrote:

> Stuart, your MacBook Air, and Dave, your MBP, do they only contain SSD, not ordinary spinning disks?

Yes for me. In the MacBook Air, there's actually no room for a traditional hard drive. 

> For any old Linux box, with several TB of HD, will investing in an SSD really make much different? 

It depends on the use. Several TB of SSD will cost you. I'd consider these issues:

1. Random access v sequential access - if you are accessing data sequentially, as is common in e.g., video processing, bioinformatics, etc. then disk latency doesn't really matter. There could be a bandwidth issue (see #2) if the processing is light, but if it is intensive, there really is little benefit. Random access, e.g., databases, file systems, gain significantly, as they don't spend time waiting for the disk heads to move to the right places. 

2. Bandwidth - a second major benefit of SSD is increased data bandwidth. That can be significant if you have a decent processor, but then a RAID array might deliver enough data to keep the system more than busy. Most SSDs are constructed like mini RAID arrays because horizontal scaling doesn't require complex mechanical systems. I've used 8-core systems with RAID arrays for a good range of applications in information retrieval, and most of the time they were CPU bound, so SSDs would not have made them any faster. 

3. Write versus read - cheaper SSDs are much (~10x) faster for reading compared to writing, expensive ones level that out. If you're doing a lot of writing, that could be a factor, but if mostly reading, then you probably have a better price point available for the benefit.

4. Cost - SSDs are more expensive, especially high-performance ones. For terabytes of data, is it worth it? Well, it depends on how you use it - see #1 and #2 above. 

5. Power - SSDs work especially well in laptops as they don't need as much juice. 

If I really wanted a truly high performance system, I'd ask whether SSD is really the right answer, as you're still shovelling all the data through the same data channels, and I/O bandwidth could become a bottleneck. You might be better with a small cluster for some tasks. For laptops, SSDs are wonderful and there are few drawbacks, but for servers and workstations, it depends on what they are being used for. 

All the best
Stuart