Average writes to Disk

fireodo

Extra space will get longer life, more room for TRIM to work with and at todays prices it is worth the investment IMHO.

I understand that all very well - its the Researcher in me that wants to find out what the real cause of all that is! Eliminating the symptoms dont eliminate the ill (if it is one) ;-)

AndyRH

@fireodo said in Average writes to Disk:

its the Researcher in me that wants to find out what the real cause of all that is!

Agreed.
Not everyone does that. I like to know how it works too.

fireodo

@johnpoz Is this process telling you (or somebody else) something?

zpool-zroot{txg_thread_enter}

This process is doing very much writing when I use
top -SH -o write (and after that "m")

johnpoz

I see that pop up every few seconds on mine as well

But I have no idea what it is or does to be honest..

Maybe a zfs guru will chime in - that sure isn't me ;)

fireodo

@johnpoz said in Average writes to Disk:

But I have no idea what it is or does to be honest..

I googled about it but I did not find anything concludent - that's why I was asking.

Would you show me your output of iostat -d 5 6 ?

johnpoz

here you go - but I don't have a ssd, this is on a netgate sg4860

fireodo

@johnpoz said in Average writes to Disk:

here you go - but I don't have a ssd, this is on a netgate sg4860

Thanks a lot - your values are similar to mine! You have also ZFS?

johnpoz

Yeah zfs.. Like I said I agree that 20GB a day seems like a lot - if your doing your math right, etc. But even at that your typical ssd should have a long life anyway..

My desktop model sg4860 has eMMC not ssd.. Which also have limited life writes..

fireodo

@johnpoz said in Average writes to Disk:

My desktop model sg4860 has eMMC not ssd.. Which also have limited life writes..

Is that eMMC replaceable?

johnpoz

I don't think so - not easy... But I think there is something missing here on what is actually being written.

So from my understanding zpool iostat shows total since boot..

[21.05.1-RELEASE][admin@sg4860.local.lan]/: zpool iostat
               capacity     operations    bandwidth
pool        alloc   free   read  write   read  write
----------  -----  -----  -----  -----  -----  -----
zroot        969M  25.1G      0     10    645   227K
[21.05.1-RELEASE][admin@sg4860.local.lan]/:

My box has been up for days.. Since I updated it to 21.05.1

Uptime 6 Days 02 Hours 12 Minutes 47 Seconds

edit: Well that can not be since boot... Not exactly sure what that reads to be honest.. But if you have it report every 2 seconds.

[21.05.1-RELEASE][admin@sg4860.local.lan]/: zpool iostat zroot 2
               capacity     operations    bandwidth
pool        alloc   free   read  write   read  write
----------  -----  -----  -----  -----  -----  -----
zroot        970M  25.1G      0     10    645   227K
zroot        970M  25.1G      0      0      0      0
zroot        968M  25.1G      0     34      0   552K
zroot        968M  25.1G      0      0      0      0
zroot        967M  25.1G      0     35      0   624K
zroot        967M  25.1G      0      0      0      0
zroot        967M  25.1G      0      0      0      0
zroot        967M  25.1G      0     38      0   532K
zroot        967M  25.1G      0      0      0      0
zroot        967M  25.1G      0     33      0   602K
zroot        967M  25.1G      0      0      0      0
zroot        967M  25.1G      0      0      0      0
zroot        967M  25.1G      0     34      0   520K
zroot        967M  25.1G      0      0      0      0
zroot        967M  25.1G      0     33      0   618K
zroot        967M  25.1G      0      0      0      0
zroot        967M  25.1G      0      0      0      0
zroot        967M  25.1G      0     33      0   531K
zroot        967M  25.1G      0      0      0      0
zroot        967M  25.1G      0     33      0   621K
zroot        967M  25.1G      0      0      0      0
zroot        967M  25.1G      0      7      0   114K
zroot        967M  25.1G      0     24      0   415K
zroot        967M  25.1G      0      0      0      0

fireodo

@johnpoz Here is my output - I'm also no ZFS expert!
As far as I see not much different ...
zpool iostat
capacity operations bandwidth
pool alloc free read write read write

zroot 808M 11.7G 0 12 319 214K

zpool iostat zroot 2
capacity operations bandwidth
pool alloc free read write read write

zroot 807M 11.7G 0 12 319 214K
zroot 808M 11.7G 0 35 0 623K
zroot 808M 11.7G 0 30 0 432K
zroot 808M 11.7G 0 1 0 8.00K
zroot 808M 11.7G 0 0 0 0
zroot 807M 11.7G 0 36 0 535K
zroot 807M 11.7G 0 0 0 0
zroot 807M 11.7G 0 32 0 442K
zroot 807M 11.7G 0 0 0 0
zroot 807M 11.7G 0 2 0 28.0K
zroot 807M 11.7G 0 35 0 618K
zroot 807M 11.7G 0 0 0 0
zroot 807M 11.7G 0 32 0 420K
zroot 807M 11.7G 0 3 0 22.0K
zroot 807M 11.7G 0 0 0 0
zroot 807M 11.7G 0 35 0 486K
zroot 807M 11.7G 0 0 0 0
zroot 807M 11.7G 0 32 0 442K
zroot 807M 11.7G 0 0 0 7.99K
zroot 807M 11.7G 0 0 0 5.98K
zroot 807M 11.7G 0 32 0 442K
zroot 807M 11.7G 0 0 0 0
zroot 806M 11.7G 0 1 0 14.0K
zroot 806M 11.7G 0 2 0 28.0K
zroot 806M 11.7G 0 1 0 14.0K
zroot 807M 11.7G 0 33 0 442K
zroot 807M 11.7G 0 0 0 0
zroot 807M 11.7G 0 31 0 428K
zroot 807M 11.7G 0 0 0 0
zroot 807M 11.7G 0 0 0 0
zroot 807M 11.7G 0 10 0 623K
zroot 808M 11.7G 0 33 0 547K
zroot 808M 11.7G 0 35 0 498K
zroot 808M 11.7G 0 1 0 14.0K

mcury

SG-3100 - 21.05.1 - pfblockerng dnsbl python mode enabled

iostat -d 5 6

fireodo

@mcury I guess FS is UFS and not ZFS ...

mcury

@fireodo said in Average writes to Disk:

@mcury I guess FS is UFS and not ZFS ...

Indeed, UFS here, noatime in fstab

fireodo

@mcury said in Average writes to Disk:

@fireodo said in Average writes to Disk:

@mcury I guess FS is UFS and not ZFS ...

Indeed, UFS here, noatime in fstab

So it seams to cristallise that ZFS is the problem ...

keyser

@mcury said in Average writes to Disk:

SG-3100 - 21.05.1 - pfblockerng dnsbl python mode enabled

iostat -d 5 6

This is really interesting because your box does not suffer from sustained writing from UNBOUND (caused by pfBlockerNG in python mode).
That would suggest it’s a setting or configuration detail that causes the issue.

I wonder what that might be. I think my setup is fairly default, but I have pfBlockerNG creating alias lists instead of it’s own rules.

Maybe we should start a thread with pfBlockerNG configs to see if we can find the root configuration cause for sustained writing to disk in pfBlockerNG?

keyser

@keyser Just as a follow up I think I have now tried EVERY possible setting in my pfBlockerNG setup in terms of making it “quiet” on disk writes.
Nothing sticks - No lists, no logging enabled anywhere, nothing - and still I have a UNBOUND process that writes on average about 380 Kb/s to disk if python mode is enabled.
If I disable Python mode or disable pfBlockerNG in general, UNBOUND no longer does it’s sustained disk writing.

So what could cause that behavior?

fireodo

@keyser said in Average writes to Disk:

Just as a follow up I think I have now tried EVERY possible setting in my pfBlockerNG setup

Good Morning (here it is),

I do not think pfblockerNG (in my case) is the culprit - I just set up a APU2 machine that was yesterday with ZFS and now with UFS and ... voilà: the writings are GONE!

iostat -d 5 6
md0 ada0 pass0
KB/t tps MB/s KB/t tps MB/s KB/t tps MB/s
0.00 0 0.00 22.55 13 0.30 0.38 0 0.00
0.00 0 0.00 0.00 0 0.00 0.00 0 0.00
0.00 0 0.00 0.00 0 0.00 0.00 0 0.00
0.00 0 0.00 4.00 0 0.00 0.00 0 0.00
0.00 0 0.00 4.00 0 0.00 0.00 0 0.00
0.00 0 0.00 0.00 0 0.00 0.00 0 0.00

This seams to prove my suspicion from yesterday that ZFS is causing the heavy writings to disk even if no service is activated on the firewall.

PS. Here the same machine with the same config but ZFS:
iostat -d 5 6
md0 ada0 pass0
KB/t tps MB/s KB/t tps MB/s KB/t tps MB/s
0.00 1 0.00 16.67 41 0.67 0.38 0 0.00
0.00 0 0.00 11.29 26 0.28 0.00 0 0.00
0.00 0 0.00 14.13 19 0.26 0.00 0 0.00
0.00 0 0.00 12.38 21 0.25 0.00 0 0.00
0.00 0 0.00 14.70 19 0.27 0.00 0 0.00
0.00 0 0.00 14.06 21 0.29 0.00 0 0.00

Have a good trip to weekend ...
fireodo

tomashk

I hope I remember correctly, but zfs by default writes every 5 seconds if there is anything to write. Also it depends on type of write operation (synchronous or asynchronous). Because it is easy to revert copy of the pfsense configuration I changed a little zfs configuration on my device (but with it there is a little bit bigger chance of problems in case of not clean shutdown)

So for my device I changed the following:

make all writes asynchronous (probably won't help much here, but software doesn't have to wait for OS to finish writing)

zfs set sync=disabled zroot

System -> Advanced -> System Tunables - set vfs.zfs.txg.timeout to 180 - it will increase time between writes from 5s to 180s; during this time all operations will happen in RAM; but writes could happen earlier if there is too much to write (also OS is able to force writing earlier - I'm not expert so I don't know all conditions); for me write happens once or twice during said 3 minutes
because there is bigger chance of failure with 180s I made zfs to write everything twice (I have 100GB SSD so it is not problem); this won't guaranty data safety, but still (works only for newly written data - old won't be touched)

zfs set copies=2 zroot

That works for me. Please read about it before changing anything. Or at least have configuration backup before you try.

tohil

I use ZFS also but with RAM disks. this will reduce the writes to the ssd massively, right?

  KB/t tps  MB/s   KB/t tps  MB/s   KB/t tps  MB/s   KB/t tps  MB/s
  0.00   1  0.00   0.00   1  0.00  13.97   1  0.01   0.00   0  0.00
  0.00   0  0.00   0.00   0  0.00   0.00   0  0.00   0.00   0  0.00
  0.00   0  0.00   0.00   0  0.00   0.00   0  0.00   0.00   0  0.00
  0.00   0  0.00   0.00  12  0.00   7.86  23  0.18   0.00   0  0.00
  0.00   2  0.00   0.00   2  0.00   0.00   0  0.00   0.00   0  0.00
  0.00   3  0.00   0.00   0  0.00   0.00   0  0.00   0.00   0  0.00