Posted by Marc Büchel
With the introduction of the ZD-XL, storage specialist OCZ has a solution in their backpack that should help making the life of database administrators much easier, which see themselves confronted with databases that can't be accelerated anymore. When traditional methods don't help anymore OCZ's ZD-XL offers the potential to increase performance of SQL databases by up to a factor of 25.
For a few years back, storage specialist OCZ has been focused on the server and enterprise market and made its own goal to develop flexible and tailored solutions that will help to reduce a total cost of ownership and therefore provide peace of mind.
About one year ago, OCZ acquired Sanrad, a company based in Isreal, which is specialized in developing and deploying specific, integrated solutions which combine advantages of both software and hardware. Under the lead of their experienced and talented team they began to work on a solution, which combines the raw IO performance of an OCZ Z-Drive with the possibilities and opportunities of Sanrad's Software in virtual environments. Today, OCZ is going one step further and presents their approach to accelerate databases, combining an easy to deploy software.
PotentialFlash caches can not only accelerate heavily in virtualized environments, like we know it from OCZ's VXL solution. Also when it comes to databases, DBA's can expect performance explosions, when deploying flash caching solutions. Accelerating databases was possible with OCZ's VXL solution already, but since it was quite a complex process to, for example swap the TempDB partition to a flash drive, OCZ realized that there is an opportunity for potential growth in the enterprise market. Therefore the Sanrad team started to work on a solution, which makes it simple for a DBA to accelerate SQL databases by basically adding a PCI-Express flash drive to a database server and installing a specific software.
SimplicityWith the ZD-XL accelerator system engineers as well as database administrators get a tool, which they can accelerate an SQL database by up to factor of 25, whereas installing takes place in a Plug'n'Play manner. For this purpose the manufacturer offers predefined caching policies, which offer optimized caching from the first minute. Furthremore the DBA or system engineer recieves information on best practices, while installing the software. If you want to accelerate your SQL database using high performance PCIe based flash drives, the key to success is to not only to use a flash drive as caching device but also as a physical partition. This comes from the fact that Microsoft SQL Server consists of three main pillars. First of all there is the DB, which contains the actual data. Second there are the log files, which are needed in case of emergency (backup). Third is the TempDB, which is basically a swap partition and therefore used when the system runs out of memory. In reality it is best to have the TempDB as well as the log files on a physical partition and since, in most cases, it's not possible to keep a copy of the database on the flash drive, there has to be a caching layer. Furthermore there is a sophisticated cahcing algorithm, which makes sure that there is hot data in the cache all the time in order to guarantee high hit rates in the cache and therefore effectively accelerate an SQL database.
As we already mentioned, there is a caching layer between the actual SQL Server and the database. Basically this caching layer coordinates reads and writes from the SQL Server to the OCZ Z-Drive R4. The latter is a significantly faster storage device than for example a SAN. Since it is not possible to keep an exact copy of large databases in a flash cache, due to capacity constraints, the question is, which data actually needs to be cached. To address this problem, OCZ implemented a user space agent which monitors all data that is being read or written from or to the database. In the end the goal is to make sure that caching policies get altered in a way that only hot data gets stored on the flash drive and cold data remains on the slower storage device associated to the database. In other words the user space agent constantly analyzes which are the hot and which are the cold zones of a database. At the same time the caching layer receives commands which areas of the DB are to cache and which to ignore.
TCO reducedIn the past, if you wanted to accelerate an SQL Database, you either had to increase the memory of your SQL server towards terabyte regions or you had to upgrade your SAN. Both these opportunities are quite costly while the SAN upgrading also causes severe headaches, not only in the IT department of a company but also in the finance department. If at this point a DBA or a system engineer is offered the opportunity to deploy a high performance flash drive to accelerate an entire SQL environment, the cost factor gets predictable again and since the performance benefit is substantial - first use cases show at least factor of two - this solution becomes a highly attractive option, which at the end of the day leads to a lower total cost of ownership.
Last but definitely not the least, is OCZ move to upload a series of whiteboard videos to YouTube, where Chief Technology Officer explains the ZD-XL solution in detail.
English by Slobodan Simic and Marc Büchel - German by William Zwingenberger, Marc Büchel - French by Marine Degli Agosti - Italian by Francesco Daghini
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