replacing HDDs and expanding pool

[AusNASath]

Hi All,

Noob here! built this NAS on centoOS in 2012, with 4x2T drives (WD caviar green, 64MB cache). recently migrated to FreeNAS-11.2-U6. two of those drives have errors (offline or unreadable sectors). I bought two replacements: seagate barracuda 7200rpm, 256MB cache. Of my ~3.5T capacity, i'm using 2.44T. I don't need more space anytime soon, but want to architect for expansion. Would love input on two options I see and confirmation that I understand VDEV expansion properly. Options: A) in each of the mirrored VDEV, place one old and one new HDD. B) VDEV1 is all new; VDEV2 is all old. I don't know if it is better to hedge my bets on those older (but still fully working) drives by pairing the old WD with a new Seagate. Or, if mixing old&new in same VDEV would create some issue due to read-write speed differences within the same mirrored VDEV. Then, can anyone also confirm: once I am ready to expand - can I move a VDEV which is currently 2x2T mirrored, to 2x3T or 2x4T by inserting the larger capacity HDD, resilver, then inserting the 2nd larger HDD, and once 2nd resilver the VDEV will expand to larger size?

Appreciate your time to help me think through these options and confirm my understanding on VDEV expansion.

 

[Chris Moore]

Or, if mixing old&new in same VDEV would create some issue due to read-write speed differences within the same mirrored VDEV.

The maximum performance of the vdev would be limited by the slower of the two drives. What was the model number of the new Seagate drives? The 256MB cache makes me suspicious. Most of the drives with large cache like that are SMR (Shingled Magnetic Recording) and they perform horribly on any activity after the initial data is written to the drive. I had bought a couple of them by mistake and ultimately needed to replace them because their poor performance was dragging down the performance of the entire pool.

Then, can anyone also confirm: once I am ready to expand - can I move a VDEV which is currently 2x2T mirrored, to 2x3T or 2x4T by inserting the larger capacity HDD, resilver, then inserting the 2nd larger HDD, and once 2nd resilver the VDEV will expand to larger size?

That should be the default behavior of the vdev. I have been through that process several times over the years, moving from 1TB, to 2TB to 4TB drives. Never had any trouble with it myself. Resilver performance is usually slow with the SMR drives, but they are even slower on a scrub and any time data needs to be modified.

I think I addressed the pressing issues here, but if you still have questions, please ask and someone will surely chime in. We have a pretty helpful group of volunteers on the forum.

 

[AusNASath]

Happy T-day all & thanks Chris! I've been shopping now to replace the 2T SMR (confirmed) Seagates. And now thinking to go ahead and take the step up move one VDEV up to 3T, leaving my two best (no error) older drives running the other VDEV. Do you (or anyone) have an opinion about WD Red WD30EFRX 3T. On Amazon sale for $70. If anyone has better price-value option to recommend based on HDD performance characteristics, i'm all ears. And, a bit more background about my NAS use: 1) general family file storage; 2) lightroom (classic) photos, low intensity (i'm no photographer); 3) family home movies. i don't do much streaming or other intensive activities on the NAS, other than the family photos and home movies.

 

[Jessep]

At one point in time WD 3TB drives had issues, think that has been resolved.

64MB cache so not SMR.

Should be fine.

Personally not a fan of mirrors, single drive redundancy makes me edgy.

Now you can start planning your backup strategy.

 

[Johnnie Black]

WD 3TB is CMR only, currently only 2 and 6TB drives are available from WD with SMR.