UNDERSTANDING TRIM AND GARBAGE COLLECTION
This is the first 2TB SSD ever reviewed that we are aware of and, as a result, more than a simple ‘we like it or not’ is necessary to tackle some of the interesting characteristics we discovered along the way. TRIM does not function but then again, do we need it with this SSD? Performance is remarkably low at times but then again, are we expecting capacity and a storage medium or a high performing SSD?
TRIM DOES NOT FUNCTION
TRIM does not function on the Solidata K8-1920E SSD and this isn’t a surprise as most SSDs that use RAID Controllers are in the same boat. For those that aren’t too clear on TRIM, it is simply the operating system letting the SSD know that data has been deleted so it can ignore that data during garbage collection. This is necessary in a SSD as, unlike a hard drive, we cannot simply just write new information over old information without first wiping the old information from the block to be written to. Surprisingly, many RAID enthusiasts have reported no drop in performance in their system configuration without TRIM and this is the result of great garbage collection. In these cases, there is also an added benefit to the use of LSI SandForce based SSDs, as with the one in use here.
Garbage collection is the process of cleaning or wiping a block of data to prepare for new data. Unlike TRIM, which may trigger the wiping of data within 10-15 seconds, background garbage collection, for the most part, occurs during idle time, hence the name Idle Time Garbage Collection or ITGC.
As seen here, the trick of garbage collection is that a block cannot be wiped until any valid data is moved from that block to another, increasing write amplification and the necessity for over provisioning. The Solidata K8-1920E has allotted 128GB of its memory for over provisioning. Without over provisioning and garbage collection, your SSD would slow significantly once all of the memory blocks have been filled with data, even data that had technically been deleted as it had not been wiped.
HOW THE SOLIDATA K8-1920e SSD ACCOMODATES
Data entropy can be described as the randomness of data itself and not how it is written (ie sequential vs random). High entropy data is also highly incompressible. Very rarely will we ever see a system work in 100% entropic data and, if this were the case, such an SSD certainly would not be sought for such. This is where the LSI SandForce flash storage processor (or processors in this case) actually provide an advantage to this SSD. The Solidata K8-1920E SSD has four SF-1222 FSPs behind the JMicron RAID controller. As long as the data stored is less than 100% entropic, you will gain free space from that so your OP will be higher than a non-DuraWrite SSD, therefore the performance will go up as the entropy goes down. This will ensure consistent performance over the duration and reasoning why this Solidata/LSI SandForce partnership is key for this SSD.
A more detailed explanation of TRIM can be seen in one our Beginner SSD Primer Series articles, entitled ‘Garbage Collection and TRIM In SSDs Expained – An SSD Primer‘.