Question Copy Video From SSD Crawls To A Halt

[gabstero]

So I am trying to copy some video clips from an SSD to a RAID5 array on Win 10 about 15Gb.
The copying starts out well at about 350Mb/sec then after about 30sec the speed drops to a puny 1.5 Mb/s or 2 at most.

Can this be an SSD or a RAID5 array issue? How can I test this?

Thanks!
Gabster

 

[Satan-IR]

If the Windows is on any either SSD or one of the disks it would affect speeds. Repositioning while writing will decrease the performance drastically. Things like the a downloader running in parallel for example.

What brand model SSD? The initial high speed could be because of RAM caching and then it drops down. However, the sustained copying speed I think should be more than 1-2Mb/s, from any single SSD to any single HDD (not RAID).

When dealing with RAID5 one can expect a penalty and occurrence of write amplification.

Parity RAID adds a somewhat complicated need to verify and re-write parity with every write that goes to disk. This means that a RAID5 array will have to read the data, read the parity, write the data, and finally write the parity. That is a total of four operations for each effective one and this means a write penalty of four on RAID5.

One more thing is that write speed of a RAID5 depends upon the controller implementation heavily. RAID software and the actual controller play a role. I said software because you didn't mention a RAID card or the presence of a RAID controller on the motherboard.

 

[nick_v15]

Sounds like a sata controller issue.

 

[USAFRet]

What drives is this RAID 5 based on, and writing to what system?

That looks very much like the initial speed of 350MB/s is just filling up the cache, and then writing to the actual physical drives.

What happened after that initial slowdown?