preclear.sh - estimating time to run


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Been researching storage solutions and have decided that I like unRAID (at least from all I've read).

 

Been reading tons of posts from forums and wiki, so much so I can't remember where I saw what.

 

Thought I saw somewhere how to calculate how long preclear might take but of course now I can't find it anywhere.

 

Currently have the server parts on order but have the HDDs and thought I might preclear them before hand.

Put unRAID on SanDisk Cruzer and plugged it into my laptop, rebooted, came up fine, able to get to menu via http://tower

 

Plugged a USB Docking Station to laptop, put in one of the drives into it (2TB WD20EADS [have 3 of them to clear]- no jumpers required - correct?)

 

started preclear.sh and seems to be working well so far except maybe the speed.

 

pre-read is currently 32.5M/sec. (suspect because of USB docking station???)

 

So if I recall, pre-read is the fastest phase. At that speed, I'd be looking at approx 18hrs just for pre-read correct?

 

Any benchmarks on what percentage decrease the write and post-read phases would be based on 32.5M/sec ?

 

Just trying to figure out if its even worthwhile preclearing (and being without usage of my laptop) beforehand or just suck it up and wait until I get the parts and put the server together.

 

 

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Been researching storage solutions and have decided that I like unRAID (at least from all I've read).

 

Been reading tons of posts from forums and wiki, so much so I can't remember where I saw what.

 

Thought I saw somewhere how to calculate how long preclear might take but of course now I can't find it anywhere.

 

Currently have the server parts on order but have the HDDs and thought I might preclear them before hand.

Put unRAID on SanDisk Cruzer and plugged it into my laptop, rebooted, came up fine, able to get to menu via http://tower

 

Plugged a USB Docking Station to laptop, put in one of the drives into it (2TB WD20EADS [have 3 of them to clear]- no jumpers required - correct?)

 

started preclear.sh and seems to be working well so far except maybe the speed.

 

pre-read is currently 32.5M/sec. (suspect because of USB docking station???)

 

So if I recall, pre-read is the fastest phase. At that speed, I'd be looking at approx 18hrs just for pre-read correct?

 

Any benchmarks on what percentage decrease the write and post-read phases would be based on 32.5M/sec ?

 

Just trying to figure out if its even worthwhile preclearing (and being without usage of my laptop) beforehand or just suck it up and wait until I get the parts and put the server together.

 

 

No way to know, as you said, your USB port is slower than the disk connected directory to a SATA controller.  Normal read speed is somewhere around 80 MB/s.
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My 2TB EARS preclear faster than 35 hours... definitely under 30.  Hell I think without the jumper on, 1 of them had a successful preclear in around 27 hours.  Pretty sure it was even faster with the jumper in place (I didn't pay close attention when I was clearing it last week).

 

I'm using an Abit AB9 Pro motherboard with a few Rosewill PCI-E 2 port SATAII cards.

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OK, <sigh> sounds like I might just need to be patient and wait until I build the server. Since I put the order in this morning, guess I won't see it until Monday (earliest).

Just hope UPS doesn't bang up the case like they did last time. Had to RMA it to get replacement it was so bad.

 

Figure (if my thought process is correct) it'd be approx 54hrs if I got the consistent 32.5mb/s (doubtful)

 

(2TB * 1048576 [to get MB] * 3 [pre-read, write, post-read]) / 32.5 =  193583.26 secs / 3600 [to get hrs] = 53.77

 

Way too long for me to be without my laptop.

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You won't get any faster transfer over USB than what you are getting now.  The good news is it should be consistent since your slowest drive speed at the spindle would be well over 35 MB/s.  When I connect my USB drive to unRAID to pull data off, I don't get any faster than the 30s.  Running a 7200 rpm 2TB drive at full speed (120 - 70 MB/s depending on head position) I usually get 32 - 35 hours on a preclear cycle.  So, your estimate of 54 hours may be closer to 60.  And I usually run 3 cycles, not just 1.

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Wow, my newest 2 TB EARS just took 64 hours to preclear!  I think something must be wrong with it....

Or the power supply, or the cable to it, or your BIOS is set to a legacy IDE mode for that port, or your server was doing something else of a higher priority.

 

Joe L.

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  • 3 months later...

Plugged a USB Docking Station to laptop, put in one of the drives into it (2TB WD20EADS [have 3 of them to clear]- no jumpers required - correct?)

 

started preclear.sh and seems to be working well so far except maybe the speed.

 

 

Just a question, not very relevant to the thread. Did you do something specific in order to get the USB docking to allow preclear? Because i tried the exact procedure on my laptop (using an Unraid stick) and, although it sees the drive on the dock, it cannon preclear. I might add that hdparm is also not working...

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Over the last month I have precleared 8 2TB EARS drives and 3 2TB EADS drives as well as a 2TB caviar black drive.  All drives got 3 cycles except one of the EARS drives (which became almost completely non-responsive after the first preclear cycle and was RMA'd.)  The EARS and EADS drives ranged between 25 and 27 hours per cycle and the caviar black drive was just under 24 hours per cycle.  Didn't seem to matter much if the drives were on the mother board or the supermicro controllers.  Also didn't seem to be a consistent difference between the EARS and EADS drives.

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