November 10, 201312 yr I pulled this from another topic http://lime-technology.com/forum/index.php?topic=13054.1125 I'm about to buy another 2 4TB drives and intend to preclear them both at the same time. I've got a machine that can be dedicated just to preclearing and it will be running virtually stock unRAID 5.x apart from the addition of a few small-footprint apps like unMENU and screen. It has 3GB of RAM. The last time I precleared a single 4TB drive, on a machine running a ton of add-ons, but with 8GB of RAM, I was getting lots of memory errors (but no crash of the preclear process). I imagine that's because I was running out of lowmem while using the other apps. The command line I used was: preclear_disk.sh -r 65536 -w 65536 -b 25600 /dev/sdb Can someone please advise what would be the optimum or suggested command line parameters to preclear 2x 4TB drives with 3GB RAM? I guess you'd want a combination of speed + memory safety. Cheers! I wrote it, and I would not even guess. I would not use more than -b 2000 personally. You are asking it to read in 1.6 GB chunks. 65536 * 25600 Changing the parameters significantly decreases the preclear time on large drives. I have heard of OOM issues when running multiple preclears on 4TB drives. It may be that OOM is all about lowmem and difficult to work out. I am going to be preclearing 6 3TB drives at the same time on new system that only has 4GB of ECC RAM and no drives currently in it yet. I am going to preclear at minimum 3 times and keep going till I get the last 2 preclears to pass. As you can see I may be preclearing for a week or so before I get my system up and running. If I remember correctly the last time I had to preclear 3TB drives it would take almost 2 days per cycle. If I could shave some time off by changing some flag parameters that would be great. What preclear flags would you recommend? Where can I find a list of flags with their explanations? I seem to remember a flag that will skip the pre-read which would not be recommended for a single cycle but if I am running multiple cycles using the "-c NN" I would be I would be fine. The reasoning behind this was that after the post read of the fist cycle would turn around and do a pre-read of the next cycle. I had found a post about it about a year ago but can't seem to find it now.
November 10, 201312 yr When you run multiple cycles the pre-clear script automatically skips the pre-read after the first cycle. I'd run 3 at-a-time and do two sets. Doing 6 at-a-time may have memory issues.
November 10, 201312 yr Author Should I use -r, -w, -b, or any other flags that could speed up the process?
November 10, 201312 yr There's really no reason to use any of these. The only flags I ever use are -c , to set the number of cycles, and -n, which skips BOTH the pre-read and post-read => it's useful to pre-clear a "known good" drive ... perhaps one from another system that's been in use for a while, or a previous parity drive. A -n cycle takes about 1/4th the time of a full pre-clear pass. When you do multiple cycles with -c, the pre-read is automatically skipped for all cycles after the 1st.
November 10, 201312 yr Should I use -r, -w, -b, or any other flags that could speed up the process? They would not speed up the process, but they might prevent you from running out of memory when running multiple preclear's concurrently.
November 10, 201312 yr Author Should I use -r, -w, -b, or any other flags that could speed up the process? They would not speed up the process, but they might prevent you from running out of memory when running multiple preclear's concurrently. What parameters should I use for 4GB of RAM? Sent from my iPad using Tapatalk
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