Hello all,

I would like to ask if you have good experience with SSD disks used in scada applications. I am still hesitating of using it as to the limited number of RW cycles. Now, I am considering it put them into client panel PCs. But I have some applications, where it would be nice to use it even in single stations, where some datalogging and archiving is done. Would you use it in that way or would you prefer standard hard disks?

Regards,
schnek

 

I have used SSDs in production test systems and was quite happy with the results. The reason for using them was to improve the reliability of the hardware and reduce downtime, and it was quite successful in achieving that.

There is no limit on the number of read cycles. There is a limit on the number of write cycles, but that limit is a lot higher than the bare flash specs would indicate. SSDs normally have their own embedded processor and firmware which shuffle data around to different areas of the disk to provide what is called "wear levelling". This can include moving existing data to new locations to free up blocks which have been written to fewer times. This is all transparent to the OS. In typical applications, this results in the flash write life of the drive being much longer than the expected life of the rest of the PC. If you still need a longer life, then you just use a larger disk which provides more area for the wear leveling algorithms to operate on.

However, if you have a database application which continuously writes and erases very large amounts of data, then you might reach this limit sooner. This is not an issue in typical automation applications though.

The big advantage of SSDs in automation applications is that they are not as susceptible to damage from vibration or impact as conventional drives are. In automation applications, this can be a very important criteria.

The main disadvantage of SSDs is that they are more expensive than conventional drives for the same capacity. In most automation applications, this is not a problem. They are quite cheap in the smaller sizes, and most people don't need to have hundreds of gigabytes of data available on line.

In most applications, the OS and application software are the largest consumers of disk space. If you plan on using either MS Windows Vista or 7 (the two are essentially the same thing) you will be in for a shock as to how much disk space they require. They won't even fit on the smaller SSDs. If you are using MS Windows, you will need to buy a larger drive to accommodate it.

One other point is read and write speeds. The specs for these are typically much better than for conventional drives. However, the drive will slow down after it has been in use for a while because it becomes fragmented. Normally though, even a fragmented drive is faster than a conventional drive. Drive speed is seldom a problem for automation applications, but it is something to keep in mind if speed was one of the reasons why you were looking at SSDs.