What size drive should I use?

September 19, 2014

I was going to call this “size does matter” … but out of respect for the young lady who vets these posts I won’t go there :-)

So this is all about the issue of choosing the right size drives to suit your performance requirements. Now a lot of people just choose the number of drives based on capacity, and what overall size they need, but there are a few considerations that should be looked at when it comes to size of drive and performance. I’ll break this into two sections – spinning media and SSD:

Spinning Media …

As a general statement (bound to cause me some grief), the performance of spinning media is pretty much the same across a family of drives, no matter what the size. If you look at something like Seagate’s Constellation 2 SATA drives, they quote seek, read and write speeds of exactly the same numbers for 250GB up to 2TB drives. So while they get bigger, they don’t get faster.

So why does this matter. Well, in spinning media RAID arrays, generally the number of spindles has a major impact on the performance of the array. For example, a mirror (2 drives of 6TB drives – 6GTB capacity) will not be anywhere near as fast in streaming data as 8 x 1TB drives in a RAID 5 (7TB capacity or thereabouts). The additional spindles in the RAID 5 allow for small reads and writes from each drive, speeding things up considerably.

To do some really rough maths on streaming data – if a drive does 120MB/sec read speed, then theoretically the best speed you can get from the mirror is 240MB/sec and from the RAID5 is would be 840MB/sec. That’s all in a perfect world of course, but you get the idea.

Of course, the RAID configuration matters and needs to suit the data type you are building for, but in general, with spinning media, you can say that more spindles equals more performance. Yes, there are power usage considerations, and cost considerations (though not a great deal), and those all need to be taken into account, but I’m talking about performance here, so stay focused on that side of the equation.


On the SSD side of the equation, there is in fact a big difference between the performance numbers of a small drive vs those of a large drive. Yes there are cost differences as well, but let’s look at the numbers …

Looking at Intel’s DC3500 SSD (a very, very good product imho), there is not a great deal of difference in the IOPs speed from the 80GB to the 800GB drives (70K to 75K respectively), but in the streaming speed there are some pretty dramatic differences. The 80GB drive claims a sequential read speed of 340MB/sec, while the 800GB drives claims a sequential read speed of 500MB/sec. The write speed difference is even more dramatic, with the 80GB drive writing at a claimed 100MB/sec, and the 800GB drive writing at a claimed 450MB/sec.

So why does this matter? Continue reading


It’s a regular blogathon at PMC …

September 17, 2014

Corporate “asked” me if they could link to this blog. That’s a bit like the wife asking “Do I look good in this?” … we all know the answer to that one :-)

So where is it linking to, and what’s in there? Well http://blog.pmcs.com/ is the place of pace at PMC … these boys really know their technical stuff and there’s terminology in there that I need Google to get me through, but it shows the breadth and depth of the technical teams at PMC – from our simple RAID cards, through SSD controllers all the way to “OTN” (Optical Transport Networks – I think).

Now these guys know their stuff, and this is one heck of an informative blog if you are interested in this stuff.

So I’ll just stick to RAID and waffling about our products, but if you want the duck’s guts on what PMC is up to, take a look at our corporate blog … I’ll have to go and read it myself :-)



I’ve never done this before …

September 17, 2014

All IT Support Tech’s know the feeling … a new customer, a new machine, a new environment and you’re under pressure to fix the beeping screaming in the back corner (and that’s just the customer … wait till you get to the server).

I’ve been there and done that. Back in the day I had to stumble my way through Novell 3.11 servers that I had little idea how to operate, and spent many a night reading books and playing with the server on my own time to get my skills up to date to support the box. Unfortunately I was in a position of the customer not having a support contract, and I didn’t have anyone friendly that I could call to discuss how to even get it working in the first place … a very, very painful situation.

You might be finding the same situation with VMware or Xenserver today – all of a sudden you are being called on to fix something that you are not 100% comfortable with.

Now of course Google comes to the rescue big time in today’s environment – you can find just about anything you need to know if you know what to search for. Then once you sort the chaff from the oats and work out exactly which video clip or document is going to be the most help you still have to actually implement the solution or make the changes – all with a racing heartbeat and a certain amount of sweat on the brow.

And so it goes with RAID …

A lot of techs don’t know much about RAID, or they are familiar with one particular vendor’s management software and BIOS screens, but have no idea about another’s and their different terminology.

So what to do? …

Google? Yes, that works, but it still leaves some doubt. Why not call and talk to someone who can help? Now there’s a novel idea – actually talking to an individual. Email works as well but generally takes longer as the tech normally never provides quite enough information for the vendor to make an informed judgment and recommendation.

So next time you are faced with a RAID issue on an Adaptec card … or you just want to know how it works and what your options are … give us a call.





Documentation Infocenter (our best-kept secret) …

September 11, 2014

You’ve just got to love it when you find out stuff accidentally … of course it would be better to be told this stuff but them’s the breaks so to speak.

Was trolling around in our website (as you do) when I came across the “Documentation Infocenter” … which is a new section buried in the support pages of our website. This is a new tool that brings all documentation for a single product into a single tool – which is searchable. Continue reading