I was on my way to Singapore yesterday. At the departure lounge, I just started reading “Data Center Storage” by Hubbert Smith (ISBN#: 978-1439834879) yesterday and I learned something very interesting immediately. Then my thoughts started stirring and I thought I have a bit of fun with what I have learned from the book.
The single, most significant piece of the storage solution is the hard disk drive (HDD). Regardless of SAN or NAS protocols, the data is stored and served from the hard disk drives. And there are 4 key metrics of a HDD, which are
- Price
- Performance
- Capacity
- Power
As storage professionals, we are often challenged to deliver the best storage solution to meet the customer’s requirements. Therefore, it is not about providing the fastest IOPS or the best availability or the lowest price. It is about providing the best balance of the 4 key metrics above.
The 4 metrics are of little help when they are standalone but if they are combined in relation to each other, you as a customer, can obtain some measurable ratios that will be useful to size for a requirements, keeping the balance of the 4 key metrics better defined rather than getting fluff and BS from the storage vendor.
In the book, the following table was displayed and I found it to be extremely useful:
| Key Ratios for HDDs |
Ratio |
| Performance/Price | IOPS/$ |
| Performance/Power | IOPS/watt |
| Capacity/Price | GB/$ |
| Capacity/Power | GB/watt |
The relational ratios in red are going to be useful in determining the right type of storage for the requirement. And we will come back to this later. We begin our quest to obtain the information that we want – Performance, Capacity, Price, Power.
Capacity is the easy one because it is a given fact the size of the HDDs.
IOPS for each type of HDDs is also easy to obtain. See table below:
| Disk Type | RPM | IOPS Range |
| SATA | 5,400 | 50-75 |
| SATA | 7,200 | 75-100 |
| SAS/FC | 10,000 | 100-125 |
| SAS/FC | 15,000 | 175-200 |
| SSD | N/A | 5,000-10,000 |
The watt of each HDDs is also quite easy. Just ask the vendor to give the specification of the HDDs.
The pricing part would be part where we can have a bit of fun with the storage vendor. Usually, storage vendors do not release the price of a single HDD in the quotation. The total price is lumped together with everything else, making it harder to decipher the price. So, what can the customer do?
Easy. Get 4-5 quotations from the storage vendor, each with different type of HDDs. This is the customer’s rights. For example, I have created several fictitious quotations, each with a different type of HDDs/SSD and pricing.
Quote #1 (SATA 7200 RPM)
Quote #2 (SAS 10,000 RPM)
Quote #3 (SAS 15,000 RPM)
Quote #4 (SSD)
From the 4 quotations, we cannot ascertain the true price of a single disk, but we can assume that the 12 units HDDs/SSDs take up 50% of the entire quotation. With all things being equal, especially the quantity of 12, we can establish the very rough estimate of the price. Having fun asking the storage vendor to run around with the quotations is the added bonus.
But we can derive the following figures (rough estimates but useful when we apply them to the key ratios above)
1TB SATA = 3333.33; 300GB 10,000 RPM SAS = 5000.00; 300GB 15,000 RPM SAS = 6250.00; 100GB SSD = 10416.66
When we juxtapose the information that we have collected i.e. price, performance and capacity (ok, I am skipping power/watt because I am lazy to find out), we come up with a table below:
In the boxed area, we can now easily determine which HDDs/SSDs that give the best value for money either Performance/$ or Capacity/$. The higher the key ratio, the better the value.
From this aspect, the customer can now determine methodically which type of disk he should invest into, in order to get the best value.
This is just a very simplistic method to find the value of the storage solution to be purchased. Bear in mind that there are many other factors to consider as well, such as rack unit height, total power consumption, storage efficiency, data protection and many more.
I am not taking credit for what Hufferd Smith has proposed. All kudos to him but I am using his method to apply to what is relevant to us on the field.
In conclusion, the customer won’t be baffled and confused thinking that they got the best deal at lowest price or fastest performance. This crude method can help turn perception into something that is more concrete and analytical. It’s time we, as customer, know our rights, and know what we are buying into and have a bit of fun too with the storage vendor.
