# Tips for diagnosing and speeding up large backup
**URL:** https://forum.duplicati.com/t/tips-for-diagnosing-and-speeding-up-large-backup/10199
**Category:** Uncategorized
**Created:** [July 1, 2020, 8:05pm UTC](https://forum.duplicati.com/t/tips-for-diagnosing-and-speeding-up-large-backup/10199 "2020-07-01T20:05:20Z")
**Posts on this page:** 2
**Page:** 1
### Author:  [@andrew-m-j](https://forum.duplicati.com/u/andrew-m-j)
#### Post date: [July 1, 2020, 8:05pm UTC](https://forum.duplicati.com/t/tips-for-diagnosing-and-speeding-up-large-backup/10199/1 "2020-07-01T20:05:20Z")
I’ve be running several backup jobs on a few computers. I had a large backup job that never ended up completing, and have since split it up into smaller jobs, but one remains ~500 GB. When I started the job I got between 1-2 MB/s according to the Duplicati interface, but after a short while it slowed to \< 1 MB/s. I have seen it get as low as 500 KB/s in previous attempts at this large backup task.
I’ve increased the dblock size to 150 MB and the block size to 5 MB. I’m working in Mac OS, to OneDrive. The computer is older, only 2 cores, 8 GB of RAM, and the source files are on an external hard drive.
I’m trying to find out where my slowdowns are so that I can speed up these large tasks (instead of having them take days and then stall out). I know the incremental backups will be much faster later. I have been using the OS activity monitor to check CPU % and RAM usage; in both cases they don’t seem fully utilized. Are there any settings I should modify, or other setups I could use to check for problems and speed up the process?
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### Author:  [@drwtsn32](https://forum.duplicati.com/u/drwtsn32)
#### Post date: [July 4, 2020, 2:14pm UTC](https://forum.duplicati.com/t/tips-for-diagnosing-and-speeding-up-large-backup/10199/2 "2020-07-04T14:14:48Z")
Hello and welcome to the forum!
I notice you are backing up data that is on an external (USB?) hard drive. I know from experience with some other backup products, using multiple readers on a single USB drive can reduce performance. I do not have experience with Duplicati backing up from a USB drive myself, but perhaps you can try adjusting the concurrency (threading) options to see if it makes a difference.
Try setting concurrency-max-threads to 1. Also maybe set concurrency-block-hashers and concurrency-compressors to 1.
I could be off base here, but thought I’d give you an idea to try since no one else has responded yet.
Good luck!