File copy stalls on L1 flush to disk on external drive.

Found a bug? Report here
Post Reply
RobF99
Level 8
Level 8
Posts: 130
Joined: Fri Sep 19, 2014 5:14 am

File copy stalls on L1 flush to disk on external drive.

Post by RobF99 »

Windows OS:7
Hardware Information
    CPU: I7
    Main Board:
    Memory:32
    Hard Drives:
PrimoCache Version:4.1.0
Screenshot(s) of your PrimoCache's main dialog showing cache configuration and statistics:

I run backups using a program called SyncBack onto an external SSD - 4 Tb. I have L1 write for 15 seconds with Average Mode. 128 Kb block size. Flush L1 to L2 is checked.

I don't use a backup method but instead directory mirroring so that it makes an exact copy and therefore copies the actual files.

I find that when the backup is copying files to the external drive, if the deferred blocks get to above 20,000 and starts to flush then the backup file copy does not progress and will not progress until all of the write data is flushed. Once the data is flushed the the file copy progresses. I notice this also happens with other write modes too. I have not seen a pattern exactly when it happens. Sometimes it can get up to 40,000 unwritten blocks and then I have to wait for all of those to flush before it resumes. Sometimes it can happen at around 15,000 blocks. So it is kind of random in its behavior. It also does not try to write to L2 in the meantime. It just waits until all blocks are flushed before it continues.

Also important is that it doesn't happen until a file has been copied and before the next file is set to be copied. So it doesn't happen during a file copy, just between file copies.

Thanks.
User avatar
Support
Support Team
Support Team
Posts: 3623
Joined: Sun Dec 21, 2008 2:42 am

Re: File copy stalls on L1 flush to disk on external drive.

Post by Support »

The option "Flush L1 to L2" applies when specified defer-write latency hasn't expired. If the latency has expired, this means all deferred write data , whether in L1 or L2, should be flushed into disks.
I think this problem is caused because flushing occupies too much CPU utilization or disk IOs, leading to the temporary stall on file copies. We are working to tune flushing process and try to make it not affect other tasks.
Thanks.
Post Reply