Should you be using SSD?

July 8, 2015

Came across a customer the other day who (remaining nameless) was using some sort of fancy data capture software in heavy industry – data logging large amounts of data from rolling mills etc. The software vendor indicated that SATA drives were not acceptable, and that the RAID system needed to use 15K SAS drives in a RAID 10 array to provide acceptable performance to allow for “maximum capture of logging data”.

So we were discussing how to set up a system – and I indicated that I thought SSD would be the best way to go here. Capture large numbers of small writes – which then get moved on to a database at a point in time (so the data volume is not great). It was all about speed of small writes. So when I suggested that we use SSD (SATA) I found it very surprising that the customer told me the software vendor had indicated no, SSD should not be used – they should use 15K SAS spinning media in a RAID array.

Hmmm … how does the software application (a Windows app) know what sort of drives are underpinning the storage? We take a bunch of drives and combine them into a RAID array. We present that logical drive to the OS and handle all the reads and writes via our own on-board RAID processor. I can understand that the application can measure the speed of the storage (write speed in this case) and judge it to be sufficient or not, but it can’t see what sort of drives are attached – that’s hidden from a properly-written application.

Considering this system will be in a very computer-unfriendly industrial environment, I would have thought that using drives that can handle vibration (there will be lots of that), don’t use lots of power nor generate a lot of heat … along with having by far the highest writing speed of the drives that a user could choose for this application, would be the ducks guts for this job.

So … my guess is that the recommendation on the software vendor’s website for using 15K SAS drives is probably 5-10 years old and would have made a lot of sense back then, but now it’s just plain out of date. If this isn’t an ideal application for 4 x SSDs on a 71605E in a RAID 10 I don’t know what is.

Lessons to be learned from this:

  1. Information on websites is not always up to date.
  2. Not everyone has jumped on the SSD bandwagon yet.
  3. You need to do a lot of investigation with vendors to find out what options you have for innovative storage solutions in today’s fast-moving environment.
  4. Telling me stuff ends up on a blog :-)

Enough said …

Ciao
N

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