We have been offering the 32GB Intel X25-E Solid State Drive (SSD) for a couple months now ($60 a month each) and have been seeing a great response overall. Now, we have also started offering the 64GB Intel X25-E for $110 a month. There have been a few regularly asked questions about these drives, so I figured I'd get them answered in a single blog post here.
Q) What are the advantages of a SSD?
A) A SSD may not achieve much higher throughput (~200 MB/sec), but the throughput of a drive is never the real bottleneck in a server environment. On a standard SATA drive, the only time you will achieve the maximum throughput is on sequential reads or sequential writes, when the drive is reading a single large group of data. The issue is, on servers, you're going to be reading data from across the disks and doing both reading and writing operations. This is where the SSD serves a major advantage, as it will get you actual read/write latencies of ~0.1ms as opposed to ~12ms on 7200RPM SATA drives or ~6ms on 15k RPM SAS drives. This means the number of IO operations you can perform a second increases tremendously. As an example, in a standard database IO benchmark, the X25-E will perform ~5000 IO/sec while a 15k RPM SAS drive will max out at around 120 IO/sec.
Not only are these drives faster, but they are significantly more reliable. As the drives store the data on flash memory modules instead of on physical platters there is no mechanical motion, as you would have in a standard hard drive. There is no risk of any mechanical failure, such as a platter getting physically damaged, of a motor going out, etc. In addition, the drives use less power, and thus create less heat, decreasing the risk of heat related issues all around.
Q) Don't SSD's have a limited lifespan or decrease in performance as they get full?
Yes, they do have a set limited lifespan, as each block can only be written to a certain number of times. To help prevent this issue, there is logic built into the drive to spread out the writes and there are also additional blocks on the drive in excess of the rated drive capacity to be used in case certain blocks are reaching their limits, etc. With these measures, the 32GB X25-E drives we use would last 50 years if you wrote 100GB a day to them and the 64GB drives would last twice as long.
Regarding the decreasing performance, this is one of the reasons we selected the X25-E drives. Yes, it is true that most SSD's will decrease in speed as they reach 80-90% of their capacity, as there will be less blocks it is able to write to. Since the X25-E is an enterprise drive, it has the additional capacity, outside of the rated size, specifically for this use, and to increase longevity. You'll see in the benchmarks from Tom's Hardware, linked to below, that there is no speed decrease on the Intel X25-E as the drive fills up.
Q) Why should I spend the extra money on a SSD? They seem expensive.
Disk IO is generally one of the first bottlenecks you'll run into on a dedicated server if you're using it for any database based sites/services. As you can see from the above benchmarks, the IO/sec rate you'll get from a SSD is about 42 times higher than what you can expect from a 15k SAS drive. Now, even if you don't need that kind of performance, you would be looking at a significantly lower cost to get 2x 32GB SSDs in RAID 1 ($135 a month) than it would cost to get 6 15k RPM disks in RAID 10 ($230 a month) and would still achieve ~7 times higher disk IO. This higher disk IO may prevent you from needing to get an additional server or needing to re-engineer your applications, saving you significant time and money.
Now, one of the issues you may have is regarding the amount of disk space you need. In most cases, what you'll be looking to offload is database caused disk IO or some other specific application. In those cases, you can just have an SSD added to your system for that specific use, and not need to worry about running out of space for your other applications that may require additional disk space. In addition, if you do need more disk space, you can always put more SSDs into a RAID array.
Q) Why did you select the Intel X25-E drives when there are more affordable solid state drives available?
A) We had looked at a wide array of drives to offer, but the Intel X25-E stood out. The X25-E offers significantly faster random write speeds than any other SSD we tested. This then made the X25-E drives the best overall value for write intensive applications, such as MySQL databases, etc. In addition, the X25-E is specifically made as an enterprise drive, and has additional features to increase lifespan and reliability as were mentioned above. This combination of speed and reliability made the X25-E an easy choice.
For more information you can check out the Tom's Hardware article and review of the X25-E: http://www.tomshardware.com/reviews/intel-x25-e-ssd,2158.html
If you have any additional question, please post them as a comment to this blog post, so we can share the answer with everyone.
Update: Tom's Hardware did a further review April 30th, comparing a couple additional solid state drives, and the results are pretty amazing: http://www.tomshardware.com/reviews/256gb-samsung-ssd,2265-9.html