TRIM Performance:
While SSDs offer many benefits, there are some downsides to using flash memory. One of the biggest issues people run into is performance degradation. Over time, an SSD will run out of fresh blocks and will have to write over data the file system has marked as deleted. This procedure is very complicated and can slow an SSD's write speeds considerably.
To address this problem, most manufacturers have added TRIM support to their SSDs. The TRIM command allows an operating system, such as Windows 7, to tell an SSD which data blocks are no longer in use. Using this information, the drive proactively erases these blocks and adds them to the free block pool.
To test the S55's TRIM function, I first put the drive in a "dirty" state. I used Iometer to fill the entire drive and then ran a random write test for about 30 minutes. This had very little effect on the S55's read speed. However, its average write speed dropped to 73.9 MB/s.
Silicon Power S55 240GB - Dirty
To see how well the S55 could recover, I let the computer sit for a couple of hours and then reran the test. The drive wasn't able to reach the factory fresh performance shown in our earlier tests. However, its average write speed climbed up to 233.1 MB/s.
Silicon Power S55 240GB - After Trim
Lastly, I used Parted Magic to perform a secure erase on the S55. With the drive wiped clean, its write speed jumped back up to 294.2 MB/s.
Silicon Power S55 240GB - Secure Erase
Final Thoughts:
Silicon Power's new Slim S55 SSD is a great choice for the cost-conscious consumer looking to improve the performance of their existing desktop, notebook or tablet computer. Powered by Phison's PS3108 controller, this ultra-slim drive combines MLC NAND flash with a sizeable DRAM cache to deliver a fast and responsive computing experience. In our sequential read and write tests, the S55 was able to read at speeds as high as 556 MB/s and write at speeds in excess of 360 MB/s. It also did relatively well in our random write tests, producing more than 57,000 IOPS at low queue depths. Given, these numbers aren't nearly as high as what we saw with Silicon Power's Slim S70 SSD, but the S55 is still a huge step up over traditional hard drives.
While the Velox V55 is available at Amazon, I could not find the Slim S55 in stock at any of the major US retailers. If the S55 is priced similarly, the 120GB drive should run about $70 with the 240GB version reviewed here going for as little as $100 when it finally ships.
Highs:
- Available in 60GB, 120GB, 240GB and 480GB capacities
- Slim 7mm form factor
- Phison PS3108-S8 controller
- Good sequential and random read and write performance
- SATA 6Gb/s interface
- Supports SMART, TRIM and Garbage Collection
- Well constructed design
- Reasonably priced
- 3 year warranty
Lows:
- Not as fast when writing incompressible data
- Hard to find in some markets
