How often do you run a parity check and do you think monthly is necessary?


ashman70

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Just curious, my biggest unRAID server with dual parity takes (which is a backup server and runs Plex and a few other dockers) a day and a half to do a parity check and while that really isn't that big of a deal in of itself, I am curious about what others do and think about how often a parity check should be run. I could tolerate running it every two months, is that too long? Am I taking too big a risk by waiting that long? If I dropped down to a single parity drive would it reduce the parity check time by half or more?

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2 hours ago, ashman70 said:

Just curious, my biggest unRAID server with dual parity takes (which is a backup server and runs Plex and a few other dockers) a day and a half to do a parity check and while that really isn't that big of a deal in of itself, I am curious about what others do and think about how often a parity check should be run. I could tolerate running it every two months, is that too long? Am I taking too big a risk by waiting that long? If I dropped down to a single parity drive would it reduce the parity check time by half or more?

How often you run a parity check is really up to you.   In theory parity checks are completely optional, but they are seen as a way of getting early visibility of potential problems.

 

in terms of elapsed time it is the size of the largest parity drive that is the key determinant of the time it will take - not whether you have dual or single parity.

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I am doing parity checks every 2-3 months.

 

Always do one before and after any disk / hardware activity.

 

Between parity checks, I do md5 verification runs, which serve a similar purpose to parity check, but they check for file corruption instead of parity corruption.

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  • 2 weeks later...

@SSD Can you explain how you do the md5 verification.

 

The parity check on my unraid machine takes more than 36h to run, so i am looking for an early warning system for problems.
The drives now all have auto error correction/bad sector swap, but they need to be 'told' that there is a problem and that can be done by reading everything on the drive.

 

I love Spinrite by Steve Gibson to do drive maintenance with but the current version is to slow to run on the modern drives, waiting for version 6.1 so i can do drive maintenance on my unraid drives.

 

Currently running unraid version 6.3.5 with 8x 4TB data disk and 1x 4TB parity disk

 

Rob

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Running smart tests on all drives now, will report.

 

Yesterday i got my weekly Array health report back with all OK.
 I though that the longer parity check was caused by the addition of new data drive.

Parity check i ran at oct 2nd was 10h / 109 MB/s

 

Don't have any other parity check reports any more, deleted them. Will archive them from now on to see the trend

 

Report back when smart tests are done

 

Rob

 

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Nothing really jumps out, you're using a SASLP, not really a good performer but there's only 4 disks there, so not a big bottleneck, there also appears to be disk activity during the checks, make sure you do it once without any activity, disable mover, etc.

 

Also, it's taking longer than expected but not as long as you said:

 

Oct 23 01:00:01 mediaserver kernel: md: recovery thread: check P ...
....
Oct 23 22:48:12 mediaserver kernel: md: sync done. time=78490sec
Oct 23 22:48:12 mediaserver kernel: md: recovery thread: completion status: 0

So ~22hours

 

And the canceled check was canceled on the same day, not the next:

 

Oct 30 01:00:01 mediaserver kernel: md: recovery thread: check P ...
...
Oct 30 20:29:55 mediaserver kernel: md: md_do_sync: got signal, exit...
Oct 30 20:29:55 mediaserver kernel: md: recovery thread: completion status: -4

 

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At the time i cancelled the last parity check it was at about 45% if i remember correctly.

 

I will change my backup of the computer and pauze sabnzbd during the parity check. Now i only need a way to pauze radarr and sonarr from scanning during the parity check.

 

Rob. 

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7 hours ago, rvank said:

The parity check on my unraid machine takes more than 36h to run, so i am looking for an early warning system for problems.

Currently running unraid version 6.3.5 with 8x 4TB data disk and 1x 4TB parity disk

 

My Parity checks with 6 4TB HGST drives was easily under 9 hours. Hell, even my mixed 6*4TB+3*8TB Parity Check is half your parity check time.

 

2017-04-01, 11:43:17 -- 8 hr, 43 min, 16 sec -- 127.4 MB/s = 6 * 4TB HGST

 

2017-07-01, 21:17:13 -- 18 hr, 17 min, 12 sec -- 121.5 MB/s = 6 * 4TB HGST + 3 * 8TB Seagate Archival

 

2017-10-24, 10:47:46 -- 15 hr, 37 min, 32 sec -- 142.2 MB/s = 4 * 8TB Seagate Archival

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23 hours ago, rvank said:

The parity check on my unraid machine takes more than 36h to run, so i am looking for an early warning system for problems.

 

36 hours on a 4TB parity drive is definitely way too long.  It takes less than 16 hours with my 8TB parity drive in my main system and 10.5 hours on my backup system with a 4TB drive.  They are both 7200 RPM drives so, if you have 5400 RPM drives it could takes a bit longer; however, not 36 hours.  Something else is an issue.  Have you tried a different SATA cable or a different motherboard SATA port for the parity drive?

 

Parity check times are not a function of how many data disks you have.  All other things being "normal" the size and speed of the parity drive itself and the speed of your slowest disks are the biggest factors in how long the process will take.

 

If other disk or CPU-intensive processes are running at the same time, that will impact speed, but your 36 hours is more than three times longer than it should take with a 4TB parity drive.  If SMART reports are all good and you are not seeing errors on any disks that would indicate cabling issues, something else has changed since your 10 hour parity run on Oct. 2.  That is more like what it should be with a 4TB parity disk.

Edited by Hoopster
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On 10/18/2017 at 5:26 PM, Zonediver said:

I do these checks every 3 months because they take a long time and need much energy.

It takes around 12 hours with single-parity.

If there is something with the Cables or HDDs, i always do a check after fixing all problems.

 

Hi wondering if you manually check every three months or schedule it via the GUI, im currently set for monthly but would like to change it to every 2 maybe 3 months

the gui seems a bit confusing when i set to custom, it appears with Every Day and Every week then pick your months.

too me it sounds like it will literally do this every single day in the months i pick

 

59fa0905ae5c7_ScreenShot2017-11-01at11_46_53AM.png.df07f508a4b3a144cbf63e939fb25935.png

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16 minutes ago, Can0nfan said:

 

Hi wondering if you manually check every three months or schedule it via the GUI, im currently set for monthly but would like to change it to every 2 maybe 3 months

the gui seems a bit confusing when i set to custom, it appears with Every Day and Every week then pick your months.

too me it sounds like it will literally do this every single day in the months i pick

 

59fa0905ae5c7_ScreenShot2017-11-01at11_46_53AM.png.df07f508a4b3a144cbf63e939fb25935.png

 

I do it manually

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12 minutes ago, Zonediver said:

 

I do it manually

 

 

I see...I did apply the config I posted and so far it hasnt tried to run parity check. under my current setup I guess I'll have to wait to December to check

 

Devs' what I would like to see is more options under monthly like you can for hourly in the mover.

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15 minutes ago, Can0nfan said:

 

 

I see...I did apply the config I posted and so far it hasnt tried to run parity check. under my current setup I guess I'll have to wait to December to check

 

Devs' what I would like to see is more options under monthly like you can for hourly in the mover.

This would run a check on the first Tuesday of every other month at 0030 hours. What else would you like to customize?

 

765BA874-F568-4B63-B226-F6749C6DCEFF.thumb.png.75dbad80118c84d805b056d3a0d46898.png

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