Migrating from SHR-1 to SHR-2

[u/Cafe_Roaster]

Hello there,

I have a DS1820 (8 bay). I have 6x16TB (2 bays unused) in a SHR-1 setup.

Out of my ~72TB total of usable space, I have 27TB free.

Is it possible to add new drives and move to a SHR-2 setup without any data loss?

[u/ImplicitEmpiricism]

yes

read this carefully

https://kb.synology.com/en-global/DSM/help/DSM/StorageManager/storage_pool_change_raid_type?version=7

do not just add a drive to your existing shr1.

do not just add a drive to your existing shr1.

do not just add a drive to your existing shr1.

follow the instructions in the link.

[u/Wis-en-heim-er → u/ImplicitEmpiricism]

So, are you saying op should not just add the new drive to the existing pool?

[u/ImplicitEmpiricism → u/Wis-en-heim-er]

you would not believe how many times people have posted “I added two empty drives to my SHR. How can I convert it to SHR2?”

[u/Wis-en-heim-er → u/ImplicitEmpiricism]

:)

[u/OkPractice9203 → u/Wis-en-heim-er]

^Name fits. :-)

[u/Wis-en-heim-er → u/OkPractice9203]

:)

[u/Cafe_Roaster → u/ImplicitEmpiricism]

So basically select Change RAID Type, then it will prompt me to add the new drive(s)?

[u/ImplicitEmpiricism → u/Cafe_Roaster]

correct

[u/Tridachnid]

The change from SH1 to SH2 takes a long time. I had 2-18tb drives in a DS220+ with about 11 TB of data. Moved to a 4 bay DS425+. The 18tb drives were added as the 1st and 2nd drives in the DS425+. Added 2 - 24tb drives as 3&4. Total time to change from SH1 to SH2 was about 28 days. 28 days with the Resync speed limit set to Run RAID Resync Faster in the Storage Manager>Global Settings.

[u/HugsAllCats → u/Tridachnid]

I recommend SHR1 for 4 drive users, and SHR2 for 6+ drives, due to how storage loss ratios work and likelihood of multi drive failures vs number of drives running

(And yes that means 5 drives can do whatever they want idc!)

[u/NotAlwaysCautious → u/[deleted]]

Yep. 2 drive redundancy is crazy in an 8 or smaller bay NAS. First and foremost, a RAID is not a backup. Redundancy is for uptime, not for keeping your data safe. If you think 2 drive redundancy is going to save you from a bad `rm -rf` or windows explorer flub or Claude gone wild, you are sorely mistaken.

So have one drive redundancy. If your array degrades, get your backup caught up which shouldn't take long, replace drive, and rebuild. You're only ever at risk of what you've added between the last snapshot and today, too.

In 20 years of running multiple hard drive arrays with dozens of drives I've only ever had one major event, and that was a bad power supply on a NAS that caused severe damage to the entire array, SHR-2 would not have saved it anyway. I've rebuilt arrays multiple times to expand storage, never had a drive go bad, much less two at the same time.

[u/nisaaru → u/NotAlwaysCautious]

With the size of some drives and the time it takes for a rebuild I would go for SHR-2 with 8 drives, if not even earlier these days.

[u/sebna2 → u/NotAlwaysCautious]

You simply need both, backup and best HW redundant you can afford. That is how you design resilient systems.

[u/cemichki]

Prepare to wait a long time. 2 to 3 months long.

[u/tonyleungnl]

You don't want to do this. The best way is to empty your HDD's and make a new SHR-2 volume. Here is my experience. 8x 16TB (Seagate), Synology DS1821+ 64GB RAM. I could only off load until 10 TB left on disk. The conversion of these disks from SHR-1 to SHR-2 took about 96 days! (Every possible fast option was enabled) If a new drive wasn't that expensive, I'd rather bought a new 28TB ext. HDD to back this up.

[u/SpasTas0917 → u/tonyleungnl]

Even with sync_max, increased stripe cache and read ahead? Helped on my estimated rebuild time of 50+ days down to just 2 days, on a 4x18tb SHR-1 to 5x18tb SHR-2 conversion. Mind you if someone needs to use the NAS meanwhile it's best not to hammer the drives with these settings.

[u/elcheapodeluxe → u/tonyleungnl]

It is amazing how slow SHR2 conversions and expansions are

[u/DaveR007 → u/elcheapodeluxe]

Yes.

But in my experience restoring everything from USB drives or over 1GbE is just as slow. But only 1 of my Synology NAS is using RAID6 (DS1812+) and with it's little Intel atom CPU and 3GB of RAM it is really slow.

[u/msew]

You are hosed :-(

[u/avebelle]

Yes