Synology DiskStation DS1525+: capacity calculator
By Devin Chua · Data checked by Owen Nakamura · Updated In the Synology DiskStation DS1525+ with 5 × 8 TB in SHR you keep 29.10 TiB usable (32 TB in drive-maker terms), surviving 1 drive failing. The calculator below is preset to the 5 bays and the RAID types DSM 7.3 or newer actually offers on this model (including SHR, which uses mixed drive sizes), with the cost to fill in Canadian dollars from live Amazon.ca prices.
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Preset for the DS1525+: 5 bays, and only the RAID types this model actually supports.
SHR (Synology Hybrid RAID)
That is 32 TB the way drive makers label capacity. Your NAS shows you the smaller number because it counts in powers of two.
Drives: from CA$2,520 for 5 × 8 TB (CA$63.01/TB overall)
What to know about the DS1525+
Five bays is the interesting number: only from five drives does SHR-2 with double fault tolerance become economical without giving up more than a third of the capacity. Unlike the DS925+, the DS1525+ takes a 10-gigabit card.
The DS1525+ at a glance
| Bays | 5 × 3.5-inch SATA and 2.5-inch SATA SSD |
|---|---|
| Maximum raw capacity | 120 TB 5 × 24 TB, per the manufacturer |
| Processor | AMD Ryzen V1500B (4 cores, 8 threads) |
| Memory | 8 GB stock, DDR4 ECC SO-DIMM (2 slots) 32 GB official, ECC |
| M.2 NVMe | 2 slots 2 × M.2 NVMe. For both cache and storage pool Synology still requires a listed NVMe drive. |
| Network | 2 × 2.5GbE, expandable to 10GbE with the E10G22-T1-Mini |
| RAID types | SHR, SHR-2, Basic, JBOD, RAID 0, RAID 1, RAID 5, RAID 6, RAID 10 |
| Third-party drives | with a caveat Partly open, like the DS925+. Since DSM 7.3 (8 October 2025) third-party hard drives and SATA SSDs are unrestricted again; only M.2 NVMe stays tied to the Synology list. |
SHR is the real reason to buy the DS1525+
SHR subtracts only the largest drive from the total, instead of sizing to the smallest like RAID 5. On the DS1525+ that means you can start with two drives, add a larger one later, and actually use the gain. UGREEN and QNAP have no equivalent, and with mismatched drives that freedom is quickly worth several hundred dollars. With equal-size drives SHR is arithmetically the same as RAID 5, so there it is simply preference.
RAID 5 or RAID 6 across the DS1525+'s 5 bays?
With 5 bays the DS1525+ gives you the choice. RAID 5 (or SHR) leaves 4 of 5 drives as usable capacity and survives one failure; RAID 6 spends one more drive for two. The rule of thumb: from 16 TB drives up, the rebuild after a failure runs so long — easily a full day — that a second failure in that window stops being theoretical. That is when RAID 6 earns its cost on the DS1525+.
Which drives belong in the DS1525+?
CMR NAS drives rated for 24/7 use — Seagate IronWolf, WD Red Plus, Toshiba N300 or their Pro variants. Our drive picks for the DS1525+ with live prices show which of those currently offers the best capacity per dollar. If you are working back from a target capacity instead, the drive-count calculator works out how many drives you need.
Frequently asked questions
How much storage is left in the DS1525+ with 5 × 8 TB?
About 29.10 TiB usable — 32 TB in drive-maker terms — computed in SHR, the sensible default for this model. It survives 1 drive failing. The gap from the 40 TB raw goes to parity.
Which RAID types does the DS1525+ support?
DSM 7.3 or newer offers SHR, SHR-2, Basic, JBOD, RAID 0, RAID 1, RAID 5, RAID 6, RAID 10 on the DS1525+. SHR is the one that matters: it lets the DS1525+ use mixed drive sizes instead of leveling every drive down to the smallest.
Can I put third-party drives in the DS1525+?
Partly open, like the DS925+. Since DSM 7.3 (8 October 2025) third-party hard drives and SATA SSDs are unrestricted again; only M.2 NVMe stays tied to the Synology list.
How much memory does the DS1525+ take?
It ships with 8 GB (DDR4 ECC SO-DIMM (2 slots)). 32 GB official, ECC There are 2 slots.
Why does my NAS show less than the calculator says?
Because the maker and the OS count differently. A drive maker calls one trillion bytes a TB; the NAS counts in powers of two and calls that a TiB — about 9 percent less. That is why this calculator leads with the TiB figure: it is the number you will read off the screen.
Devin Chua works out which drives, RAM and NVMe cache fit which NAS model at nasdrives.ca, and what the RAID choice means for usable capacity, checked against what is in stock on Amazon.ca.
Data checked by Owen Nakamura, Technical editor (data checking)