How does setting the Compression flag for drives affect read/write speed?

[Vitalius]

Hi guys,

Let's say I have two 120GB SSD's in RAID 0 (to combine both volume and speed), but I set that drive to be compressed. How would this influence read/write speeds?

I copied a 5GB file there from a single SSD, and I saw it start out at 200-300MB/s, but then peter down to 50MB/s at 25% done, then kick back up to 300MB/s twice before falling back to 50MB/s.

Just curious. I plan to use this drive to record gameplay video to, so I wanted to know how compressing it might affect the performance. And possibly the quality (720p24).

Thanks,
Vitalius

[brob]

NTFS compression is lossless so quality is not afected. However performance is. CPU resources are required to compress and uncompress the data. It is also of questionable benefit.

 

SSD compress data to save space. The saved space is not reported as available to the system. Rather it is used to improve wear leveling on the drive. Using NTFS compression means more can be stored on the drive. But at the cost of less space available to extend life of the drive.

 

But this behavior may explain the variable performance you noted. When data is compressed by the o/s the SSD cannot compress it any further and so has to write the entire amount. If an o/s uncompressed block is written, the SSD can compress then write it. Because the SSD compressed the block, the write may be faster (less to write).

[Vitalius]

NTFS compression is lossless so quality is not afected. However performance is. CPU resources are required to compress and uncompress the data. It is also of questionable benefit.

 

SSD compress data to save space. The saved space is not reported as available to the system. Rather it is used to improve wear leveling on the drive. Using NTFS compression means more can be stored on the drive. But at the cost of less space available to extend life of the drive.

 

But this behavior may explain the variable performance you noted. When data is compressed by the o/s the SSD cannot compress it any further and so has to write the entire amount. If an o/s uncompressed block is written, the SSD can compress then write it. Because the SSD compressed the block, the write may be faster (less to write).

That was a great & concise explanation. Thanks. Disabling it now.