Can SSD performance degrade over time and is there a way to prevent this? The answer is YES and YES. the same solution that addresses the inefficiencies of iops in Windows , SQL and VMs can also help you to maintain the performance of your solid state disks.
The reason for this degradation is an undesirable SSD phenomenon called the Write Amplification Factor (WAF), . This is a numerical value that indicates the actual amount of data that was written to an SSD in relation to the amount of data that was requested to be written from the Host (i.e. Windows OS System)
WAF = the data written to the SSD / the data written by the host
For example, an application on the Windows Server system writes out 128kb of data to the SSD, but internally on the SSD, 512kb of data is written on the SSD for this to occur. This will degrade SSDs write performance.
In this example, the WAF = 512kb/128kb = 4 ! This is bad, a 128kb write from the host that resulted in 512kb of internal writes on the SSD
Ideally, you want a WAF = 128KB/128KB = 1
Why does this occur. Unlike HDDs, data cannot be directly overwritten on a disk. On SSDs, data can only be written to erased spaces. When you have a brand new initialized SSD, all of the pages are in a free/erased state, and there is no problem for it to find free/erased spaces to write new data. But as the SSD starts to fill up with data, resulting in erased spaces having to be created that causes the WAF to increase. I can go into more detail on this but will save it for another time. Suffice to say, a higher WAF value means SSD performance degradation.
Do SSDs degrade over time?
The answer is YES but this has to do more with the SSDs filling up over time. Some recommendations on the web advise to keep free space on SSDs anywhere from 10% to 30% to avoid this degradation. With less free space on a highly I/O intensive system, a couple of things occur:
-There are less free spaces to write to, extra overhead may have to occur like block erasures to allow the new updates to occur. This increases the WAF – Not a good thing.
– With less free space, file data may get spread out to different locations on the SSD. For example, in the best case, 10 pages of file data that is being updated are all on the same block.
– When the block needs to be erased to be updated, then just that one block needs to be updated. If those 10 pages are on 10 different blocks, then in the worst case, those 10 blocks have to be erased and re-written – More overhead and a higher WAF.
The result is
➣SSDs are overprovisioned. For example, a 1TB SSD actually contains 1.1TB of data space. This extra space (seen only by the SSD internals) helps to allow the WAF to remain low.
➣SSD Garbage collection and Trim. Both of these processes include freeing/erasing spaces in the background so new writes can occur quickly on these newly erased spaces.
How doies DymaxIO™ help with SSDs Degrading?
DymaxIO has technology to keep the WAF low.
The patented IntelliWrite® technology enforces efficient Sequential Writes to occur rather than smaller Random Writes from the Windows Host. Sequential writes are more likely to place data in the same blocks which can decrease the WAF –
Optimization engines keep the free space contiguous when needed on the host logical side. This will help enforce larger sequential writes to occur which decrease the WAF.
There are also a few more benefits of enforcing larger sequential writes.
– Sequential I/Os out-perform Random I/Os on storage, both HDDs and SSDs, so this ensures you are getting the optimal performance from your storage.
– Keeping the WAF low and writes lower on the SSD helps to extend the lifetime of the SSD.
IntelliWrite technology in DymaxIO does both of these functions automatically
– Keep sufficient free space on your SSDs
– Enforce Sequential Writes rather than Random Writes.
Fix at the source. 2X SQL application performance, accelerate Windows throughput 40+%, extend hardware life 2 to 3 years, reduce timeouts, crashes, and more. A software solution to software problems Just install, DymaxIOno code changes, no reboot necessary.
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