Raid 0 (128k) – Cache Write-Back Enabled/Disabled
Now we have left the single disk territory and are in RAID land, the Intel controller has a nice feature called “Cache Write-Back” which Intel recommends you enable for an extra performance boost. (Cache Write-Back = CWB)
How much of a boost can we expect?
(#we’ll repeat the benchmark descriptions, for quick reference and to help those jumping through random pages to find their way#)AS SSD BenchmarkAS SSD Benchmark
. A raw translation of the German details below:
The synthetic tests to determine the sequential and random read and write performance of the SSD. These tests are carried out without the use of the operating system caches. In the program Seq-test measures how long it takes to read a 1 GB large file, respectively, to write. In the 4K test will determine the read and write performance for random 4K blocks. The 4K-64-THRD-test corresponds to the 4K procedure except that the read and write operations are spread across 64 threads (typical start of a program).
In all three synthetic test is the test file size of 1GB. Last, still determines the access time of the SSD, the access of which is determined to read through the entire capacity of the SSD (Full Stroke). Write access test only to be met with a 1 GB big test file.
First up are READ speeds:
With the CWB enabled we see a small boost in sequential read speed, but random performance is slightly slower. Latency remains approx. the same.
Write performance with CWB doesn’t impress. No dramatic drops in throughput, write access times does increase by ~20%. But seeing as we’re in the 0.xx milliseconds area here, it’s hardly dramatic.
Next up the “normal” copy/paste tests, which don’t bypass the OS cache;
In the copy test (menu Tool-copy benchmark) the following test folders are created: (ISO) two large files, programs) (typical program folder with many small files) and games (folder of a game with small and large files. These three folders are copied with a simple copy command of the operating system. The cache is turned on for this test.
With CWB we see a noticeable boost in this test, COPY game gets +60%, COPY ISO not really worth mentioning.HD Tune
The synthetic benchmark HD Tune
is more widely known.
Sequential read performance gets a very nice boost with CWB enabled, up to 2x faster!
Sequential write doesn’t get a large boost with CWB but noticeable nonetheless.
The Random Access tests display average throughput using different size file chunks:
Enabling CWB has no positive effect on random read/write performance; worse case scenario a ~20% drop.FC TestFC Test
, or File-Copy Test is a small straight forward application. You can measure the time it takes to create files of different size, then measure how long it takes to copy them between volumes, and also measure how long it takes to delete them. For our test we were interested in the write/creation speeds. So we used the PROG,WIN,MP3 and ISO templates to measure the disk speed.
The real world tests shows a 13~17% performance increase with CWB.PassMark
The last benchmark used in this article is PassMark
, a system benchmark tool which sports a quite complete HDD performance test. Allowing you to define different “worker” threads that can replicate “real world” drive usage. We used PassMark patterns: Database, FileServer and Workstation, we also created a custom random write thread.Database: 10% Sequential / 90% Random IO, 90% Read / 10% Write, 2k file chunks, Asynchronous 128 queue
FileServer: 0% Sequential / 100% Random IO, 80% Read / 20% Write, 16Kb file chunks, Asynchronous 128 queue
Workstation: 20% Sequential / 80% Random IO, 70% Read / 30% Write, 16Kb file chunks, Synchronous
Custom: 0% Sequential / 100% Random IO, 0% Read / 100% Write, 4k file chunks, Synchronous
With small file chunks and random operations the CWB doesn’t help performance, but as the file chunks get bigger the CWB does pay off, a 30% “free” performance boost.
Summary? Just enable it, it won’t do any harm, worse case scenario you won’t notice a difference, best case scenario you get a nice throughput boost.