Super User is a question and answer site for computer enthusiasts and power users. It's 100% free, no registration required.

Sign up
Here's how it works:
  1. Anybody can ask a question
  2. Anybody can answer
  3. The best answers are voted up and rise to the top

I have a NAS where I have temporarily stored about 2.2TB of data while I rebuilt my “heavy lifter” workstation. My heavy lifter has no SATA on-board, but I use an LSI 9550sx-12 PCI-X RAID card for my on-board RAID-5 array (five drives in total: 3 in array, one hotspare plugged in and one coldspare in drawer). For the first time, I decided to use a SATA drive (on the LSI card, port 0) for my boot drive instead of using an IDE drive (my needs are not great, I don’t need performance all that much).

What I am experiencing now, however, is a great big problem: When I transfer my data back onto my RAID-5 array (my D: drive, newly created with brand new drives), it is completely soaking my main boot drive (my C: drive) -- 100% active time, almost 0kb/s disk transfer rate. Why?

None of the other single drives attached to the LSI card (E:, temp storage; F:, a staging drive for BitTorrent and other duties) are being soaked -- only the boot drive. This is causing massive latency in almost every running program, as my main boot drive is almost completely unresponsive until the data transfer is finished. Plus, the drive doesn’t get soaked until about 2-5 minutes into the transfer, and remains soaked until about 2-5 minutes after the data has completed being transferred to my D: drive (the data transfer window shuts down).

FYI, I am using Windows 8. Just as an experiment, nothing more.

share|improve this question
Use Resource Monitor to find out which file the I/O is going to. – David Marshall Jun 15 '13 at 16:45
Sorted by file path under Disk Activity, turned off almost every single running program that was accessing C:, nothing gave me a total B/sec over 20K. On the other hand, D: was still being hammered with multiple file copy actions with total access speeds of 300K+B/sec (some at 400K+). The Write column was particularly telling -- nothing with a file path under C: was showing significant amounts, yet the drive itself was still “soaked” in the graphs. – René Kåbis Jun 15 '13 at 17:23
By 'soaked' I assume you mean 100% utilisation. – David Marshall Jun 15 '13 at 17:30
Technically, yes. Under Windows 8, you have a separation of stats in the Task Manager, and this is carried over to the graphical display of the Resource Monitor. One is called Active Time, “Percentage of time the disk is processing read or write requests”. That is sitting at 100%. The other is called Disk Transfer Rate, “Read and write activity on this disk”. This is sitting at close to 0KB/sec, especially when I am not doing anything else (like operating a web browser). – René Kåbis Jun 15 '13 at 18:15
My D: drive (the destination for the data) is also showing 100% active time, but unlike C: drive it is also showing relatively high disk transfer rate, on the order of 3-4MB/sec. So this is really confusing me - why is C: showing 100% active time when there is virtually nothing being written to or read from the drive? All the action is clearly on D:, and yet C: is being soaked to the point of rendering the entire system unusable. – René Kåbis Jun 15 '13 at 18:16

Have you tried a tool like:

WinDirStat ( to know which files are taking up the room?

It seems like the client you use to copy doesn't copy it directly to the D: drive and instead temporarily puts it in C:

Which client and protocol do you use for transferring ?

share|improve this answer
(part 1): The problem with WinDirStat is that it is so drive-intensive that the move operation would complete long before that program would be allowed to finish. Remember -- my C: drive is getting utterly soaked. Starting any sort of a program takes about 15 minutes. Do something unusual in any program, and it locks up (not responding) for anywhere from thirty seconds to five minutes. Any attempt by any program to access C: is delayed and slowed down by (at least!) a factor of 100. – René Kåbis Jun 15 '13 at 17:08
(part 2): I have also confirmed that there is no change in drive usage from before a move operation to during the move by looking at the properties of the drive itself (right-click -> Properties). All I am using is the basic Windows Explorer file copy/move functionality. That is, I am dragging and dropping from my NAS onto the D: drive, with the shift held down to change a copy to a move. – René Kåbis Jun 15 '13 at 17:11

Your Answer


By posting your answer, you agree to the privacy policy and terms of service.

Not the answer you're looking for? Browse other questions tagged or ask your own question.