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MyDigitalSSD MLC Drive

MyDigitalSSD is a private label MLC drive distributed by MyDigitalDiscount of Oswego, New York.

The basic design suggests two basic problems when this drive is used as a bare device without MFT. The first of these is that the MLC version has a very slow native random write speed: +/- 4 random writes per second. This is the same speed as is found on MLC USB sticks as well as CF Cards. This is troubling as linear write speed is a very good (for MLC) 56mb/sec. The other dramatic problem with the drive when used in native mode is that the device uses an 8mb erase block. This means that for each random write, 8mb of data have to be written. On the one hand, this explains the high random write rate. On the other, using an 8mb erase block, rather than the 2mb used by most other manufacturers, means that the write life of the drive is reduced by a factor of 4.

In short, we would strongly discourage use of this device without MFT except for specific applications. These would be any environments where the drive is to be either used almost exclusively read only (possibly, some web servers), or where the drive will be used together with large video or sound image on demand systems. Here, the drive's extremely low cost combined with its high linear speeds are desirable.

For general computing use, this product must be used with MFT. And what is exciting is that when it is used with MFT, its effective speed improves 183-fold (see Aggregate results) to a level somewhat above CF cards, and soundly in the middle-ground of performance. Just as importantly, MFT overcomes the wear problems of this device. While the expected write life of most flash devices improve somewhat more than 50-fold, when used with MFT this drive's life actually improves over 200-fold, because MFT negates the disadvantage of the 8mb erase block design choice. Even more interesting is the notion that if the manufacturer of this drive were able to speed up the very slow random access speed, performance of this device using MFT would probably accelerate a further 3- to 4-fold, making it a top performer in the MLC class and almost on par with fast SLC drives. Thus, it demonstrates how MFT can give designers freedom to make radical design choices.

Because of the very large erase block size of this device, we don't really recommend the use of this device in large arrays.  For example, with a raid-5 array of 8 drives, this would create an "effective erase block size of 56 MB ( (8 drives - 1) * 8 MB ).  While MFT does handle this situation, MFT's kernel memory footprint starts to get large and the array can get a bit "bursty" as reads are locked out during writes that can take many milliseconds.  While these drives are unquestionably good solutions at up to 4 drives, larger arrays should be tested before any large scale deployment.

MyDigitalSSD MLC Drive Manufacturer's Specifications
My Digital SSD
Manufacturer's Page http://MyDigitalSSD.com
Manufacturer's Warranty 1 Years
Flash Media Type MLC
Flash Media Erase Life 10,000
Size 2.5"
Case Metal (Plastic for IDE)
Format SATA-I and IDE
Linear Read Speed 120mb/sec
Linear Write Speed 56mb/sec
Access Time 0.43ms (slow!)
Sizes and Models
16GB 2.5" 16
32GB 2.5" 32
64GB 2.5" 64
128gb 2.5" 128
MyDigitalSSD
Performance Results for MyDigitalSSD MLC Flash Drive
Block
Size
Random Read Tests: Random Write Tests Random Write with MFT
1 Thread 10 Threads 1 Thread 1 Thread
IOPS BW IOPS BW IOPS BW IOPS BW
4k 2,182 8.5 2,263 8.8M 4 18.3K 12,270 47.9M
8k 2,020 15.7M 2,055 16.0M 4 36.7K 6,266 48.9M
16k 1,747 27.3M 1,801 28.1M 4 75.1K 3,272 51.1M
32k 1,406 43.9M 1,446 45.2M 4 147.1K 1,662 51.9M
64k 1,020 63.8M 1,047 65.4M 4 288.0K 831 51.9M
256k 383 95.8M 390 97.5M 4 1228.7K 186 46.5M
1mb 111 111.0M 112 112.6M 4 9.5M 47 47.2M
Aggregate IOPS without MFT 13 Higher is better. A single 15,000 rpm SAS drive has a value of 250, and a 7,200 rpm SATA drive rates at 70. Click here for explanation of calculation methodology.
Aggregate IOPS with MFT 2,386
MFT Overall Performance Multiplier 183
MyDigitalSSD MLC Random Writes Permissible for 5-Year Drive Life
  7,200 rpm
SATA HDD
15,000 rpm
SAS HDD
16GB
Drive
32GB
Drive
64GB
Drive
128GB
Drive
Maximum write throughput per day without MFT 19GB 69GB 0.12GB 0.25GB 0.50GB 1.00GB
Maximum write throughput per day with MFT n/a n/a 26GB 52GB 104GB 209GB
Hours per day needed to finish read/write activity 24.00 24.00 .28 0.57 1.14 2.28
Drive Utilization Percentage 100% 100% 1% 2% 5% 10%
Thruput per day is based upon an average data size of 10.66kb and a read/write mix of 70% reads and 30% writes. The values shown for the 7,200 and 15,000 rpm Hard Disks are the maximum possible attainable values if these drives are run at 100% duty cycle 7x24. Values for the flash media are calculated as described here. Here, the limit to throughput is not time, but rather the number of safely available write cycles based upon a goal-life of at least five years.
Distributors Offering this Product Bundled with MFT