Can NAS storage pools be directly expanded by adding hard drives? My cousin put in a 4TB block, but the usable capacity didn't increase by a single byte

cousin's four-bay Synology machine, after a round of repairs last year and replacing it with a broken unit, now has two 4T Cool Wolf set mirror arrays in the cabinet, with the other two bays empty. Not long ago, Movie Kuga Photos was about to use up the 4TB available capacity, so he placed an order for a 4TB block. When it arrived, he slotted it into the empty spot. Synology clicked step by step in the backend and got a prompt for expansion successful—the available capacity was still 4TB, not a single byte had increased. His exact message to me was, "Did I buy a fake list?"

first, distinguish: having a space doesn't mean you have capacity just because you add it

drive doesn't take effect immediately after being plugged in. For Synology's types that can add to old pools, the official documentation clearly states: JBOD, RAID 5, RAID 6, SHR with at least two disks—adding to the pool increases capacity. RAID 1 is also on the list of add-ons, but with a terrible little note— adding hard drives to RAID 1 won't increase capacity, .

cousin stepped on this very thing. The two 4TB drives are RAID 1, meaning the two drives are mirrored together, and the available capacity is always equal to one drive. Add a third 4TB drive, and Synology accepts it all, making the three drives into three-channel mutual backup—safety is indeed higher, if two disks fail, no data loss, and usable capacity remains 4TB. I spent over 400 yuan on a "more stable" device, which is like spending money at all for a home movie storage machine.

the root of this was on the day the PC was installed. If you had built the pool according to the beginner's recommended SHR deck, two 4T blocks would have been 4T, and now adding a third 4T would instantly increase to 8T, doubling the amount. How to choose between SHR and RAID 1, and how to calculate mixed storage drives— I once calculated with 4TB and 8TB, so I won't repeat it here. By the way, don't rush to spend money when the day is full. my 4TB Feiniu cleaned a circle of , and the snapshots, recycle bin, and Docker logs combined brought back over 400GB. This cleaning step is zero-cost.

Which pools can you add, and how much does it change after adding: a chart to understand

first put the account on the table, add one 4T to the three common pools, and what happens if you put them in:

pattern is simple: pools order validation (SHR, RAID 5) increase by removing redundancy by ; Pure mirror pools (RAID 1) are adding up, increasing redundancy shares, while capacity remains stagnant. When chose RAID back then, how I took the line directly decided whether today's buying was just a bargain or a wasted effort.

there's another rule that's easy to overlook: for new projects added to the SHR pool, the capacity must be greater than or equal to the smallest part of the pool. For example, if the pool is 2T, 2T, or 4T SHR, if you add an 8T chunk, the extra portion won't be used. So don't be stingy with extra bets—buy according to the largest piece in the pool, or you'll waste the price difference. My cousin was lucky; both of his pools were 4T, and the new one he bought was also 4T, so at least he didn't get caught up in this one.

Synology buying is a two-step process. After clicking the first step, don't rush to close the page

When

helped him check, I flipped through the official documentation and tutorials. The complete process for adding a disk to the pool in Synology 7.x actually consists of two parts:

first paragraph, expand the storage pool. In Storage Manager, select Lao Chi, click the three dots in the upper right corner, choose 'Add Hard Drive,' check the box for the newly inserted drive, and confirm. After this step, the pool grows, but you still don't see the new capacity in the file system—many people get confused at this point, thinking they've failed again.

the second paragraph, expand storage space. After the pool is expanded, the storage (volumes) is still stuck at the old size, so you need to expand the storage space again to push the file system to the new pool size, and only then will the capacity truly fall into your hands. Sometimes Synology will proactively pop up prompts to guide you to step two, sometimes it doesn't. Pay attention to whether the storage space section still shows the old capacity.

time-consuming needs to be anticipated. Adding a new account isn't just about formatting the new account; the validation data for the entire pool must be rearranged across the board, with both old and new accounts written together. My cousin's three-panel 4TB mirror array can't get on the right path. I used Synology users' records for reference: SHR with three drives plus one 4TB usually takes over ten to twenty hours to reboot, which is on the same scale as rebuilding a whole drive. During this time, the machine worked as usual, but the speed was noticeably weaker. SMB copying files and Jellyfin database scanning slowed down by a beat.

the Customs of Expansion Day: Wait if you can, don't add fuel to the fire

rescheduled these days, there are a few things I specifically reminded him to remember.

first, don't run big projects. Reorder for full-disk read/write. At this point, arrange a full backup or a few TB download tasks, with both sides competing for disk, dragging rescheduling from one day to three days. My lesson was that backup tasks and hard drive rework were scheduled at different times, the about checking the stolen drive was specifically recorded for this record.

Second, don't cut off the power. During rescheduling, redundancy remains, and a broken drive doesn't lose data, but if the power suddenly goes out, you might have to redo the rearrangement from scratch, wasting more than ten hours. If your Synology machine doesn't have a UPS, make up for this lesson the night before expansion. I caught when the RAID rebuilt to 62% and broke down, and I didn't want to go back again.

third, don't be reckless and add drama halfway. Halfway through the rearrangement, I found another seat still empty, so I thought I might as well add two at once—no, I'll add one at a time, and after the run is stable, I'll add the next. It's the same as changing one block at a time for expansion.

Feiniu takes a different approach: there's no 'Add Hard Drive' button

my own N100 dual-drive Feiniu, the choice at full drive is different from that of Synology users. In Feiniu's graphical interface storage management, the official expansion method is to replace the large drive one by one—remove the small one, plug in the large disk, wait for the array to be repaired, then replace the next drive, and manually expand the capacity once after all replacements. Synology's approach of "directly adding to the old pond" is two different approaches.

trying to push drives into old banks on Feiniu isn't impossible. In the command line, mdadm drives are added, LVM is expanded, and file systems are supported. This whole setup can be done, and there are complete tutorials available online. But let me leave it this way: command line expansion has too low tolerance for error. If you mistype one drive letter, it's a whole different story. Regular players shouldn't touch this path. I mentioned in the about Feiniu and Synology function reconciliation, Feiniu really still has a breath to be sung in array online expansion.

So, for Feiniu users with available slots, the most practical method is actually the second method: don't move the old library, hang the new as a separate storage space, move the movie library over, and focus on photos and documents. Zero risk, done in ten minutes, but the cost is that the two pools are managed separately, and shared folders have to be moved over.

Seats are full but budget is empty: Try the three backup options in order

if all the slots are full, or like RAID 1, where adding pools is pointless, these are the next few points to go down:

clear first, then talk money. There are plenty of snapshots with dozens of gigabytes, uncleaned recycle bins, and Docker logs piled up for years. go through those five steps , you can probably squeeze out a buffer of about a month.

consider trading the larger market piece by piece. Replace all 4TBs with 8TBs, double the available capacity, follow the process the disc replacement and moving article the same: replace one piece at a time, fix it and replace the next. SHR's rules were also written in 928. This path is slow, but every old property can be resold for resale after retirement. Before second-hand list, clean up the data thoroughly don't skimp on this step.

really don't want to change the pool, I installed a portable hard drive on the USB port as a storage drive, storing some "no worries if lost" cold data. I've been running it for three months , just know the power supply and formatting pitfalls in advance. As for the total lack of bays and the old machine, that's a signal to upgrade. the two and four slot accounts how they calculated back then is now recalculated.

cousin's 4TB chip wasn't refunded in the end, so it was hung as a standalone download drive. The movie library was moved over, and Lao Chi freed up over 300GB to catch his breath. He said that when the movie library is full again next year, he will follow the path of switching the market. Alright, the process is all over here anyway.