Replacing my SATA HDDs with SDDs - same size - TrueNAS Scale

[thstruenas]

Hello community !

I am currently running TrueNAS Scale (TrueNAS-SCALE-22.12.3.1) and trying to figure out the best way to replace my storage HDDs with new SDDs that I have recently acquired. Both the HDDs and SDDs are of the same size - 4Tb - each. My current setup for my data vdev/Pools are 4x 4Tb WD Red NAS drives currently operating on RAIDZ2 , currently providing ~ 7Tb of total storage. I plan on replacing these with 4 x 4Tb SSDs. I also use other storage devices (nvme's) as boot as well as for my Log and Cache vdev's , however these will remain unchanged. The server (HW) will also remain unchanged, this upgrade will ONLY affect the storage HDDs.

I am currently thinking of going to each of the HDDs and shutting them off / out of my data VDEV then replacing them with the SSD's and allow TrueNAS to "resilver" them as the drives are getting replaced, but I decided to post a question since technically speaking HDD/mechanical storage works differently from SSD/Flash storage and I may be missing something on the process here. I currently don't have a separate server that I can turn on with the new SSDs and do a vdev migration, so I am asking to check what would be the best way to proceed here. Thanks in advanced for your time and attention to the matter here.

 

[sretalla]

It will "work" as you describe... but...

SSDs and HDDs probably don't have the same exact size, despite what's written on the packaging... and even worse... SSDs are probably quite a bit (more than 2GB) smaller, so you won't actually get it to work with a "like for like" size replacement.

 

[HoneyBadger]

Hello @thstruenas - as mentioned above, complications may arise if the SSDs are significantly smaller in raw size than your existing HDDs.

If you can connect a single SSD to the system and run lsblk -bd this will give you a listing of the top-level devices and their byte sizes. Compare the SSD to the HDD - if it's more than 2GB smaller, replacing "in-place" won't be possible, even with workarounds such as disabling the swap file temporarily.

If you have sufficient connectivity, you can create a second SSD based pool and copy the data over using a ZFS send.

 

[thstruenas]

It will "work" as you describe... but...

SSDs and HDDs probably don't have the same exact size, despite what's written on the packaging... and even worse... SSDs are probably quite a bit (more than 2GB) smaller, so you won't actually get it to work with a "like for like" size replacement.

Thank you for responding to my query. I will try to assess the new SSDs true size before replacing the HDDs !

 

[thstruenas]

Hello @thstruenas - as mentioned above, complications may arise if the SSDs are significantly smaller in raw size than your existing HDDs.

If you can connect a single SSD to the system and run lsblk -bd this will give you a listing of the top-level devices and their byte sizes. Compare the SSD to the HDD - if it's more than 2GB smaller, replacing "in-place" won't be possible, even with workarounds such as disabling the swap file temporarily.

If you have sufficient connectivity, you can create a second SSD based pool and copy the data over using a ZFS send.

Thanks for the info. I will plug one of the SSDs using a external enclosure just to double check the size before replacing the HDDs.