Everything You Always Wanted to Know About SSDs (But Were Afraid to Ask)

Everything You Always Wanted to Know About SSDs (But Were Afraid to Ask)While the verdict is in on SSD optimization (consolidate free space instead of defragging your SSD), we still get a lot of questions about optimizing SSD write performance with PerfectDisk. Here are some of the most useful SSD performance threads discussed in the Raxco User Community:

SSD and Free Space Consolidation – How Does This Help?

I’m thinking of getting PerfectDisk mainly for the SSD Optimize feature. It seems the only thing SSD Optimize does is free space consolidation. I’ve been reading up on this topic and till now I’m not convinced that free space consolidation can help my SSD. My understanding is that free space   consolidation has to erase and write again to lump together free space. Won’t this constant erasing and writing make a SSD drive “dirty”? Does free space consolidation have any function that resembles garbage collection, (i.e., make the free space clean so that it can be immediately written to)? Or does it have to wait for garbage collection to make the free space clean?

The SSD Optimize pass identifies the largest consolidated free space chunk already existing on your SSD and grows it. This results in a larger consolidated free space chunk on the volume – but the primary reason for doing so is to maximize the number of blocks which can be trimmed by the OS or the device. This is increases the effectiveness of garbage collection (TRIM). Watch our video explanation:

SSD Optimize vs. Free Space Consolidation

I want to make clear here that while the SSD Optimize pass effectively increases free space consolidation it should not be confused with PerfectDisk’s Free Space Consolidation optimization method for HDDs:

  • The Free Space Consolidation pass defragments files and creates a large free space gap at the end of the drive (for HDDs).
  •  The SSD Optimize pass does not defragment files and it does not consolidate free space at the end of the drive, instead it grows the largest existing gap on the volume (for SSDs).

SSD Optimize is designed to do this without creating excessive erase/write cycles – and this is evidenced by how quickly this optimization pass runs. Our SSD optimization pass won’t have your SSD churning through data and can be run as often as you like.

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How Does SSD Optimize “Grow” Free Space?

What if there is permanent data (like Windows system files) on either side of the free space?

How SSD Optimize Grows Free Space:

By moving out data into blocks that are not full. This quickly eliminates as many partially full blocks as possible. This is done using a one shot method, so there is no use of swap space (no churn). The result is a marked increase in the number of blocks which can be trimmed in exchange for incurring a single read/write cycle for a very small number of partially full blocks. If there are any free blocks that can be used to relocate data, those are used instead since this is both faster (no read/write cycle), and aids wear-leveling a bit by not writing to a previously written to block. How we determine which blocks to target and how we target them is strictly proprietary.

Of course, this is a very simplistic description of the rules that govern the behavior of the algorithm because the behavior described operates within the context of growing out the largest consolidated free space chunk and not wholly consolidating all free space. Thus, no defragmentation of either free space or files is performed. This is why the primary action is referred to as “growing” free space. Also not to be confused with “freeing up” or “recovering” free space.

This eliminates one flaw in wear-leveling and TRIM in that partially full blocks are not trimmed. Only blocks that are verified as empty are reset by the SSD (based on block boundaries). This means that when organic writes are committed to the device, the wear-leveling algorithm has more trimmed blocks to work with. This helps both TRIM to restore performance and the wear-leveling algorithm to extend the life of the device.

SSD Optimize is designed to allow TRIM and the wear-leveling algorithm on your SSD to do the best job possible – any performance benefits or improved wear-leveling are solely the responsibility of the OS and the SSD firmware. In this sense, our SSD optimization pass is in some aspects a prep pass.

Excluded “Permanent” Files:

The algorithm respects excluded data and works around it. This is true of all things PerfectDisk. Files that are exclusively locked are simply unmovable since we stick to using the system API – thus, illegal moves are not possible with PerfectDisk.

Optiwrite and SSDs

I’m wondering why OptiWrite is disabled by default on SSDs. From what I know, OptiWrite doesn’t increase write frequency, so I’d like to understand the reasoning behind this.

I do know that fragmentation is not as much an issue with SSDs, so OptiWrite isn’t as important for them. But is that the whole reason–OptiWrite on an SSD would be wasted overhead? In that case, why do any optimization at all on SSDs?

OptiWrite® is designed to prevent file fragmentation. It does so at the expense of causing free space fragmentation. While file fragmentation impacts performance on HDDs, it doesn’t necessarily cause performance issues for SSD drives and free space fragmentation can affect write performance for SSDs. That is why OptiWrite is disabled for SSD drives.

PerfectDisk Optimize settings for Hybrid Drives (8GB NAND + HDD)?

I recently bought a new 1TB Hybrid Drive for my notebook PC and am curious what, if any, considerations need to be made for how PerfectDisk optimizes it.

The SSD part of the drive is used as cache to accelerate I/O. Data does not get written to the SSD.

There are no compatibility issues and you will still need to defragment the drive as a normal (HDD) drive.

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PerfectDisk doesn’t recognize SSDs in RAID as SSDs for SSD Optimize mode?

I have two SSDs in RAID 0 and was wondering: Do I have to manually run SSD Optimize as it is not preselected?

Correct. RAIDed SSD drives are not seen by Windows as an SSD drive. Since Windows doesn’t see it as an SSD, PerfectDisk won’t either. If you double-click the drive, you can override auto-detection and tell PerfectDisk that the drive is an SSD drive.

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