What data is the right data to load on the SSD depends on the use case. For example, if most of the server's data is going to be on shared storage and the primary task of the current mechanical storage in the server is to boot the server, than an entire replacement of the mechanical hard drive to bootable SSD technology like those we discussed about in our last entry may be in order.
There is value not only in dramatically increasing the speed at which a server can come back online, there is also value in making sure memory swap files are stored on these local drives. It improves performance when the server has to page out memory and it decreases traffic across the storage network.
Another data set to consider moving to local SSD is any data set that is transient in nature. For example, these could be log files that track the transactions of a database or email application, or small files that are constantly being read from and written to. The other common culprit is the above mentioned swap files used by operating systems and applications when physical RAM has been completely allocated. As is the case with log files, these are typically small files that have very active read/write patterns.
As the performance and I/O rate of these functions increase, it may be time to consider a PCIe-based SSD that allows for an even higher speed channel to the processor. With PCIe SSD flash memory, performance can be almost as fast as DRAM. But PCIe SSD can provide over 1 TB of cost-effective solid state performance where most servers are limited to well under 500 GB of DRAM.
Putting transient files on SSD is an ideal way to improve performance without having to change an application or physically relocate more permanent files. It can provide a quick and easy performance improvement to the server and actually improve network storage performance since this traffic would no longer be traversing the SAN, freeing it up for other requests.
Another way to leverage SSD in a way that is complimentary to the SAN is to use caching software. SSD caching, similar to other forms of caching, stores the most active data in the flash SSD inside the server. What server-based SSD cache changes is the amount of data that can now be cached, which reduces the chances of a cache miss.
As we discuss in our recent article "What to Look For In A Server SSD Cache," there are many solutions now available and several vendors are providing their own software bundles. In most cases, these solutions can work with shared SAN or NAS storage and keep the most active data close to the server, which provides better application performance and once again reduces the amount of traffic that has to travel the storage network.
SSD in a server is a great place to start with SSD. It improves the boot time of the systems and it improves the performance of shared storage that those servers may be attached to. In many cases we recommend a combination of booting from SSD to bring servers back online quickly and PCIe SSD with caching software to accelerate operating system and application transient data functions.
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