Selfhosted

40296 readers

322 users here now

A place to share alternatives to popular online services that can be self-hosted without giving up privacy or locking you into a service you don't control.

Rules:

Be civil: we're here to support and learn from one another. Insults won't be tolerated. Flame wars are frowned upon.
No spam posting.
Posts have to be centered around self-hosting. There are other communities for discussing hardware or home computing. If it's not obvious why your post topic revolves around selfhosting, please include details to make it clear.
Don't duplicate the full text of your blog or github here. Just post the link for folks to click.
Submission headline should match the article title (don’t cherry-pick information from the title to fit your agenda).
No trolling.

Resources:

selfh.st Newsletter and index of selfhosted software and apps
awesome-selfhosted software
awesome-sysadmin resources
Self-Hosted Podcast from Jupiter Broadcasting

Any issues on the community? Report it using the report flag.

Questions? DM the mods!

founded 1 year ago

MODERATORS

HybridSarcasm@lemmy.world

HybridSarcasm@lemmy.hybridsarcasm.xyz

Mirror seeing half the write IOPS on one disk than the other, is this normal? (discourse.practicalzfs.com)

submitted 2 months ago* (last edited 2 months ago) by lightrush@lemmy.ca to c/selfhosted@lemmy.world

15 comments fedilink hide all child comments

I'm syncoiding from my normal RAIDz2 to a backup mirror made of 2 disks. I looked at zpool iostat and I noticed that one of the disks consistently shows less than half the write IOPS of the other:

                                        capacity     operations     bandwidth 
pool                                  alloc   free   read  write   read  write
------------------------------------  -----  -----  -----  -----  -----  -----
storage-volume-backup                 5.03T  11.3T      0    867      0   330M
  mirror-0                            5.03T  11.3T      0    867      0   330M
    wwn-0x5000c500e8736faf                -      -      0    212      0   164M
    wwn-0x5000c500e8737337                -      -      0    654      0   165M

This is also evident in iostat:

     f/s f_await  aqu-sz  %util Device
    0.00    0.00    3.48  46.2% sda
    0.00    0.00    8.10  99.7% sdb

The difference is also evident in the temperatures of the disks. The busier disk is 4 degrees warmer than the other. The disks are identical on paper and bought at the same time.

Is this behaviour expected?

you are viewing a single comment's thread
view the rest of the comments

[–] Shadow@lemmy.ca 5 points 2 months ago (1 children)

You could just swap the two disks and see if it follows the drive or the link.

If the drive, rma it. I don't put a lot of faith in smart data.

[–] lightrush@lemmy.ca 2 points 2 months ago

Turns out the on-CPU SATA controller isn't available when the NVMe slot is used. 🫢 Swapped SATA ports, no diff. Put the low IOPS disk in a good USB 3 enclosure, hooked to an on-CPU USB controller. Now things are flipped:

                                        capacity     operations     bandwidth 
pool                                  alloc   free   read  write   read  write
------------------------------------  -----  -----  -----  -----  -----  -----
storage-volume-backup                 12.6T  3.74T      0    563      0   293M
  mirror-0                            12.6T  3.74T      0    563      0   293M
    wwn-0x5000c500e8736faf                -      -      0    406      0   146M
    wwn-0x5000c500e8737337                -      -      0    156      0   146M