Replacing WD drive with 4k sectors: how?

[odedia]

Hi,
One of my drives reported failure so I had it replaced. I had 4 WD 2TB green drives in my NAS4FREE box. I now replaced the faulty drive with a WD RED model, also 2Tb.

When I setup my NAS box, I did that "advanced 4k format" checkbox to solve the 4k misalignment issue with WD drives. I think I also did .nop trick so it will work find but honestly it was so long ago that I can't remember.

Should I do anything special regarding the 4k sectors as part of the replacement process? I just followed the guide here step by step without doing anything special (Didn't even to a format of the drive because it was brand new, nas4free seemed to be fine with it).

http://www.wiki.nas4free.org/doku.php?id=faq:0149

Thanks for your help.

[odedia]

Interesting, I just took a look at the SMART panel and while the green drives show the following:

Sector Size: 512 bytes logical/physical


The RED drive shows the following:

Sector Sizes: 512 bytes logical, 4096 bytes physical

Does this mean that there are no issues at all with the RED drives in NAS4FREE? Seems that it should be able to properly identify the physical sector size and work with that, right?

[b0ssman]

you can use the wd red drive like a normal drive. if its not aligned you will loose some performance. (5-30%)

however if your array was not aligned before the creation, you cant align it afterwards

[siftu]

bOssman is right. I'm at the point of recommending that everyone use advanced format even if your drive isnt 4k drives. I think the performance hit of formatting a 512b sector drive to 4k is far less the other way around.

If I were you I would backup my data and recreate my pool with both devices as advanced format. This will also future proof you when you replace your next drive.

[b0ssman]

there is no performance hit using advanced format on a 512b drive.

only a tiny storage hit.

[odedia]

Thanks for the info,
As I said in the first post, I DID format the drives originally as 4k drives (meaning I checked the "advanced format drive" checkbox).

However, I have now replaced one drive in the pool (did a zpool replace command). The new drive was not formatted beforehand.

Should the fact that I am replacing an old 4k drive formatted drive with a new drive automatically align it correctly? Hope my question is clear...

If I had to format it as a 4k drive before doing the replace command, I can always just take that last drive offline, format it to 4k then resilver, right?

Thanks for that help.

[siftu]

Ok it sounds like your are fine then. If the output of "zdb | grep ashift" is 12 and not 9 there is no problem and you are good to go.

[siftu]

there is no performance hit using advanced format on a 512b drive.

only a tiny storage hit.

That is my suspicion but I had heard others say there is a slight performance hit. Do you have any sources or benchmarks? I would love to see the numbers myself

[odedia]

Ok it sounds like your are fine then. If the output of "zdb | grep ashift" is 12 and not 9 there is no problem and you are good to go.

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nas4free:~# zdb | grep ashift
            ashift: 12

Thanks!

[françois ROLAND]

And, is it possible to change it after replace 1 or 2 HD by WD red series?

Or should I backup my data, erase and re creat a pool ZFS using advanced format 4Kb ?

[b0ssman]

you can not change the alignment after the pool is created.

[françois ROLAND]

I tried to re create a new pool with 4x1To HD, but I checked advanced format 4k

When I remove one HD to replace it by a WD RED 2 To, I got same message :

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 state: ONLINE
status: One or more devices are configured to use a non-native block size.
        Expect reduced performance.
action: Replace affected devices with devices that support the
        configured block size, or migrate data to a properly configured
        pool.
  scan: resilvered 45K in 0h0m with 0 errors on Sat Jun 20 17:46:14 2015
config:

        NAME        STATE     READ WRITE CKSUM
        pool1       ONLINE       0     0     0
          raidz1-0  ONLINE       0     0     0
            ada0    ONLINE       0     0     0
            ada1    ONLINE       0     0     0
            ada2    ONLINE       0     0     0
            ada3    ONLINE       0     0     0  block size: 512B configured, 4096B native