preclear... does it really add anything?

[rcrh]

So, I'm 164 hours into the preclear on my 2tb drive and I'm wondering what I'm gaining for my week of time.  I've seen the threads that say "we got into trouble with a new drive", "I should have run a preclear".  But, I'm not seen anything discussion how a preclear would have helped avoid any problems. 

 

So, I'm wondering what everyone things preclear is doing that the normal SMART tests don't.

 

In the mean time I'm at 90% of step 10 and I hope it finished tonight or some time tomorrow.

 

Thanks.

Richard

[Hoopster]

Something is very wrong if it takes over 30 hours to preclear a 2TB drive.  All of my 2TB drives precleared in 24/25 hours and the 3TBs were done in 31 hours.

 

Preclear isn't your problem, something else is (SATA controller?, drive itself?)

 

The experts here will ask for your configuration information and a syslog, so, you might as well be proactive and post that information.

[rcrh]

I'm willing to bet everyone is going to point to my eSATA chassis and its port replicator.  But, I'm still surprised to see it taking this long. 

 

I'll go pull together my info.

 

Thanks.

[JonathanM]

So, I'm 164 hours into the preclear on my 2tb drive

How many passes is that? If that's the first pass, I agree with the above poster, something is very wrong. And if that's so, then you will have experienced first hand what preclear is good for, and that is finding issues with the drive BEFORE you commit your data to it.

[vca]

I have returned two WD 2TB drives because they took about 50-60 hours to preclear instead of the usual 30 hours.  So it could be that you have a marginal drive.

 

Regards,

 

Stephen

[rcrh]

So, I'm 164 hours into the preclear on my 2tb drive

How many passes is that? If that's the first pass, I agree with the above poster, something is very wrong. And if that's so, then you will have experienced first hand what preclear is good for, and that is finding issues with the drive BEFORE you commit your data to it.

 

It's one pass and every step has completed without any errors.

 

[rcrh]

I also just checked my activity monitor and noticed that three instances or preclear are running.  I'm going to double down on my bet of "port replicator" and add "user error" for 50. 

 

Is there any way to tell which two of the processes I can kill?

 

[WeeboTech]

Preclear is a good confidence test of your drive's ability to read/write data reliably.

 

The badblocks tool is even better at detecting issues (and even help correct them) since it can do a 4 pass write/read test of various patterns.

I've had bad drives come back to life by doing a badblocks 4 pass test. It exercises every sector with specific bit patterns.

 

Joe's preclear is an extremly useful utility as it captures early smart data, exercises the drive, then compares the smart data.

 

Badblocks is better in showing where and how many errors your drive has.

Joe's preclear is better in showing your drive's throughput.

 

Maybe one day we'll have the best of both worlds!

 

In any case, I would not add a drive to the array without a badblocks or a preclear test first.

 

[rcrh]

 

...In any case, I would not add a drive to the array without a badblocks or a preclear test first.

 

Thanks.

[dgaschk]

I also just checked my activity monitor and noticed that three instances or preclear are running.  I'm going to double down on my bet of "port replicator" and add "user error" for 50. 

 

Is there any way to tell which two of the processes I can kill?

 

It doesn't matter. Did you start more that one?

[rcrh]

 

... It doesn't matter. Did you start more that one?

 

I started one (maybe two) and had to close down the telnet session.  I assumed anything in the telnet session would end.  I'm guessing that's not the case.  I'll have to figure out how to "resume" a telnet session.

 

Thanks.

[JonathanM]

I started one (maybe two) and had to close down the telnet session.  I assumed anything in the telnet session would end.  I'm guessing that's not the case.  I'll have to figure out how to "resume" a telnet session.

"screen" is the command used to create a "resumable" session. If you didn't use screen, then anything in the foreground of the telnet session would end.

[rcrh]

"screen" is the command used to create a "resumable" session. If you didn't use screen, then anything in the foreground of the telnet session would end.

 

Well, I didn't use "screen" so I guess I was correct to restart the pre_clear process.  So I'm not sure why I ended up with three of them running.