% % %

Your Database Needs 3 TB of Memory. Your Server Has 2 TB of DRAM Slots. Now What?

This is the moment when the budget meeting gets tense. Option A: buy a 4-socket R860 with 64 DIMM slots at $85,000 もっと. Option B: live with the performance bottleneck. Option C was not on the table because most IT teams do not know it exists — Intel Optane Persistent Memory 300 シリーズモジュール, which plug into the same DDR5 DIMM slots as DRAM, but deliver 512 GB per module instead of 64-256 GB. Populate four Optane modules in four DDR5 channels, and you add 2 TB of memory to a server that was already full of DRAM — without adding a single DIMM slot, CPU socket, or server node.

技術仕様

パラメータ	仕様
モデル	Intel Optane Persistent Memory 300 シリーズ (Crow Pass, 4th Gen Xeon)
容量	512 GB per module (また: 128 GB, 256 GB)
Memory Technology	Intel Optane (3D XPoint) — byte-addressable, persistent, non-volatile
フォームファクタ	DDR5 DIMM (DDR-T2 interface, 288-ピン)
インタフェース	DDR5 memory bus — connects to CPU memory controller, not PCIe
Memory Mode (App Direct)	Byte-addressable persistent memory accessed via DAX (Direct Access) filesystem or PMDK library. Data survives power loss.
Memory Mode (Memory Mode)	Volatile, used as system memory with DRAM as cache. OS sees total Optane capacity as volatile RAM. DRAM acts as L4 cache.
Latency (App Direct, 4K random read)	~350 nanoseconds (vs ~90ns DRAM, ~10,000ns NVMe SSD)
帯域幅 (per module, sequential read)	~15 GB/s (DDR5-4400 equivalent)
持久力	100% of capacity written per day for 5 年 (essentially wear-out-proof for data center workloads)
力 (アイドル状態 / アクティブ)	~3W / ~15W
Data Persistence	はい (App Direct mode) — data retained across power cycles without battery backup
暗号化	AES-256 hardware encryption (always-on, transparent to OS)
Compatible CPUs	4th Gen Intel Xeon Scalable (Sapphire Rapids), LGA 4677
Max Modules per Socket	4 Optane modules + 16 DRAM DIMMs per CPU (mixed configuration)
OSサポート (Memory Mode)	ヴイエムウェア ESXi 7.0 U3+, 8.0+ \| Windowsサーバー 2022/2025 \| RHEL 9.x \| SLES 15 SP4+
OSサポート (App Direct)	RHEL 9.x, SLES 15 SP4+ (DAX filesystem), Windowsサーバー 2022+ (DAX volume)
保証	3-year (with server)

Optane PMem vs DRAM vs NVMe — The Performance Pyramid

属性	DRAM (DDR5 RDIMM)	Optane PMem 300	NVME SSD (Gen4)
Latency (4K random read)	~90 ns	~350 ns	~75,000 ns (75 us)
帯域幅	~38 GB/s (5600 MT/秒)	~15 GB/s	～7 GB/秒
Max capacity per DIMM/slot	256 GB (3DS RDIMM)	512 GB	30.72 結核 (U.3 SSD)
Cost per GB (relative)	100% (baseline)	~60%	~3%
Byte-addressable	はい (volatile)	はい (persistent)	いいえ (block storage)
Data survives power loss	いいえ	はい (App Direct mode)	はい
Best for	Active working set, hot data	Large in-memory datasets, database buffer pool extension, Redis/Memcached tier	Bulk storage, cold data, backups

Use Case: Database Buffer Pool Extension

An Oracle database with a 1.5 TB working set and a server with 1 TB of DRAM has a 500 GB gap that spills to NVMe storage — where every page fault costs 75 microseconds instead of 90 nanoseconds. With 2x Optane PMem 300 512 GB modules (1 TB total) in Memory Mode, the DRAM acts as a 1 TB cache backed by the Optane modules as the buffer pool extension. Page faults that would have gone to NVMe instead hit Optane at 350 nanoseconds — over 200x faster. The difference between a database that runs at 10,000 transactions per second and one that runs at 14,000 TPS is this 500 GB gap and how it is filled.

互換性のあるプラットフォーム

Requires 4th Gen Intel Xeon Scalable (Sapphire Rapids) processors and BIOS support for Optane PMem. Compatible with Dell PowerEdge R660, R760, R770, R860, R960, xFusion フュージョンサーバー V7 (1288H/2288H/2488H/5288/5885H). Not compatible with AMD EPYC platforms (R7715) or earlier Xeon generations (R740, R750). Verify the server BIOS has Optane PMem configuration enabled — not all system boards enable it by default.