Solid State Disks in Database Servers

by Youngmin L
Solid State Disks (SSDs) are a data storage medium using flash memory. Hard drives on the other hand use rotating platters to store data. Compared to traditional hard disks, SSDs have faster data rates, are more resistant to physical shock, run cooler & quieter, and have lower access times. Because SSDs are a young technology, they are more expensive and have less capacity than traditional hard disks.

In the past, SSDs did not have the capacity for most production uses, and they were too expensive to implement. However, within the past few years, SSDs have dropped in price significantly and storage capacity has increased. This has allowed SSDs to infiltrate consumer and enterprise devices. SSDs are now slowly being adopted for Database servers. Many servers today have an extraordinary amount of RAM and processing power to handle heavy workloads. They however have been bottlenecked by hard drives. Although hard drives have dramatically increased in capacity, they have not significantly increased in speed. This is where SSDs come in as a solution. An enterprise grade SAS hard drive running at 15,000 RPM has a transfer rate of about 200 MB/s. In comparison, a Serial ATA SSD can provide almost 600 MB/s of throughput, limited only by the bus. PCI Express (PCIe) based SSDs can provide over 3000 MB/s (3 GB/s) of throughput.

SSDs can be used in multiple ways within a storage array in a database server. SSDs can be added as a portion of the storage in an auto-tiering array, used as a cache, or used as traditional disks.

Many servers use something called auto-tiering which stores the most frequently accessed data on the fastest storage medium such as a high performance SAS hard drive. However replacing that drive with an SSD makes the “fastest storage medium” even faster. Therefore, information that is accessed the most frequently can be accessed with less delay.

Another way SSDs can be used in an Database server is using the SSD as a flash cache. When the server is configured as a flash cache, the SSD becomes the secondary layer of caching. Even though this flash cache is slower than the normal layer of caching, it is still faster than using traditional hard drives. The flash cache is ideal for systems that often access the same block of data such as an OLTP Database. It is however not ideal for systems that do not use the same blocks of data repeatedly such as an SQL Server.

Lastly, SSDs can be used as traditional disks in a database server. This is the most expensive and least flexible way to use SSDs in a storage array. In this method, SSDs completely replace traditional hard drives. This is extraordinary costly because SSDs are still much more expensive than hard disks. If parts of the database are mostly idle, putting the entire database into SSDs does not make financial sense.

SSDs can be installed onto database servers in two different ways. They can be installed in a standard drive cage, which use SATA interface, or PCI Express based SSDs can be used. PCIe based SSDs plug in directly into the motherboard. There are advantages and disadvantages of both installation methods. Installing an SSD in a drive cage is very easy to install and remove. If the server is hot swappable, SSDs can be replaced and installed without taking the server offline. Another advantage is that the motherboard’s RAID controller can handle all the disk redundancy functions instead of using a software based RAID controller. A disadvantage is that SATA based SSDs max out at 600 MB/s. This is slower than current PCIe based SSDs. PCIe based SSDs connect directly to the motherboard through PCIe slots and therefore have much higher bandwidth. However, the biggest downside to PCIe SSDs is that there is no hardware RAID controller available. This means that a software RAID solution has to be used within the operating system.

The largest benefit of implementing SSDs into a database server is the improvement of server’s I/O operations. The hard disk has been a bottleneck for a very long time and SSDs aim to fix that bottleneck. There can also be other benefits from using SSDs. Because I/O operations are very fast, the server can be able to run with less RAM. For example, if a company is running SQL Server Standard Edition, it can be cheaper to install SSDs instead of upgrading to SQL Server Enterprise Edition and adding more RAM. (SQL Server Standard Edition has a limit of 64 GB of RAM). SSDs can provide immense performance benefits but it will not fix all performance issues. Optimized code is still very important. Optimized code along with an SSD based database server will bring many benefits to any company or enterprise.

Cherry, D. (2013, January 18). Using solid state disks in sql server storage solutions. Retrieved from http://sqlmag.com/storage/using-solid-state-disks-sql-server storage-solutions

Du, Y., Xiao, N., Liu, F., & Chen, Z. (2013). CSWL: Cross-SSD wear-leveling method in SSD-based RAID systems for system endurance and performance. Journal of Computer Science and Technology, 28(1), 28-41.  doi:http://dx.doi.org/10.1007/s11390-013-1310-z

Otey, M. (2013, December 27). Hot database industry trends. Retrieved from http://sqlmag.com/sql-server-2014/hot-database-industry-trends

Riley, D. (2013, September 8). Micron p420m ssd review: 1.4 tb of pci express-attached storage. Retrieved from http://www.tomshardware.com/reviews/p420m-pci-express-ssd,3603.html

16 thoughts on “Solid State Disks in Database Servers

  • February 17, 2014 at 6:43 pm
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    I thought your article was very interesting since I had previously only known about SSD’s and their popularity in new gaming desktops. It makes sense that they are being implemented in databases for their incredibly high transfer rates as you mentioned. I also found it interesting that you mentioned installing SSDs would be cheaper than upgrading SQL Server Enterprise edition and adding more RAM since I always assumed SSDs were still highly priced and would therefore be too costly for the majority of companies.

  • February 20, 2014 at 12:21 pm
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    I really enjoyed the article, I personally have been dying to get a SSD for personal use but I did not think that they would benefit in a server based company. With the use of SSD in servers will increase production and create faster results. It amazes me how much hardware keeps improving

  • February 20, 2014 at 12:46 pm
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    This article was very informative and highly interested me because I have been in the market for a SSD. The price of SSD is dropping quickly as you have previously stated and there is evidence of this through using amazon and the website camelcamelcamel.com(which allows you to track the pricing history of any product on amazon). Using that website, the price of a 120gb SSD dropped by 35 dollars within 7 months. This article definitely helped convince me to pick up a SSD soon.

  • February 22, 2014 at 8:22 pm
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    There are now hybrid drive, which uses SSD cache, meaning that when the pc boots up it uses the ssd but otherwise uses hard drive for other non time consuming tasks. It is useful because although it is not as fast as a real ssd, it utilizes best of both worlds so that you still maintain the 1 tb or 750gb storage of the hard drives, and it costs much less

  • March 6, 2014 at 4:29 pm
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    With SSD being a popular choice in hard drives you definitely convinced me to buy one. They are only getting cheaper and its about time i joined the bandwagon and hopped on the the tech train. I recently just built my on desktop computer and i bought one just because of this article. I was skeptical at first as to whether or not i should invest in one but now that i built it and put my OS on it it runs beautifully and quite faster. Thank you again for helping me make a well informed purchase.

  • March 6, 2014 at 10:13 pm
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    I absolutely love the SSD I have! It has definitely changed made a significant improvement in the performance of my PC. It is no surprise that utilizing these in database servers would be beneficial for sustaining high rates of data flow.

  • March 11, 2014 at 2:27 pm
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    This was along time coming i was wondering when they were going to install SSD’s in servers. With this huge improvement in speed and also technology. With also the implementation of cloud computing the data we get will be ten times faster. Great Presentation BTW.

  • March 13, 2014 at 11:20 am
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    I am using ssd in my computer, so I know how much ssd speed faster than regular hard. When people use ssd in database. it can very helpful to people who acesses database. It was very interesting topic, and great presentation.

  • March 17, 2014 at 5:46 pm
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    I also use and SSD on my desktop, and it is noticeably faster than a standard hard drive. Using them in a server based system would be fantastic, but it would cost a fortune compared to normal hard drives. An SSD nowadays is going for roughly $0.75 per GB of storage, whereas a normal hard drive is around $0.06 per GB.

  • March 18, 2014 at 5:50 pm
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    Great post, using SSD for higher rate of data read/write rate is an great idea for database servers and greatly improve the performance. Just need to make sure the interface can stand the transfer rate, otherwise the bottleneck will limit the potential of SSDs. And like you mentioned the SATA and PCIe are on the motherboards therefore for big corporations with older version of motherboards( SATA and PCIe) the cost of changing over to SSD might be higher.

  • March 18, 2014 at 9:49 pm
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    This is such a great topic to talk about. I have always wanted to do more research on SSDs so it was good to hear more about them and also how they relate to databases. I’m excited to see how this technology progresses in the future.

  • March 19, 2014 at 10:16 pm
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    SSD is such an amazing and interesting topic. It is really cool to see how much of an upgrade a solid state can be to your computer. It is also really cool too see how it can help databases. That was something I did not think about when dealing with SSDs

  • March 20, 2014 at 1:36 pm
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    Very informative presentation. I did not know much about SSD drives and I’m considering getting one for my computer. I also think it is interesting that one of the models can be used through the PCI port. The price of SSD has gone down a bit over last year which makes it more appealing.

  • March 20, 2014 at 9:09 pm
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    i was thinking about to SSD for awhile ago but i don’t think that i were this it any time soon but after your presentation i just ordered one from amazon. the SSD transfer speed is amazing compare to old school hard drive. great information front the presentation.

  • March 20, 2014 at 9:27 pm
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    interesting information about this article and its uses that could be use in database servers, and take advantage of the data rate speed and resistance to shock and falls since they have no moving parts. I have upgrade my computer with one also since the price come down, and took advantage of the Thanksgiving sales and Christmas sales, now the start up and storage has increase and speed is much better than the old drive that came with it.

  • March 20, 2014 at 9:43 pm
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    I remember when I was buying my laptop, I had a choice between SSD or a HDD. I chose an HDD in the end (it had three times the capacity of the SSD offered at the time), but even still I think SSD might have been the better offer. Eventually SSDs will be superior to HDDs (in both price and performance), but seeing them currently in databases is unlikely. Sort of off topic, but does anyone know where I can find data on the two? It would be useful to quantify how much faster SSDs are to HDDs.

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