Western Digital Ultrastar DC SN655 (Capacity-tier NVMe・2024年)（ウエスタンデジタルウルトラスター）
2024年Western Digital (元WD Corp・米Irvine California・1970年Alvin Phillips創業・World HDD Number 1 share + Enterprise SSD Top 5 vendor・SanDisk 2016年買収) 発表のUltrastar DC SN655・PCIe Gen 4 x4 (Gen 5 ではなく Gen 4) Enterprise NVMe SSD・12,000 MB/s Sequential Read (PCIe Gen 4 limit theoretical 16 GB/s下) + 5,300 MB/s Sequential Write + 1.8M IOPS Random Read + 3D BiCS5 TLC (112-layer) + 1.92TB-15.36TB capacity + U.2 + EDSFF (E1.S / E3.S) ・Capacity-tier specialized (Read-intensive Capacity workload optimized 1 DWPD) ・$0.10-$0.13/GB Mid-Premium Capacity tier。
概要
Western Digital Ultrastar DC SN655 は、2024年Western Digital Corporation (米Irvine California本社・1970年Alvin Phillips創業・World HDD Number 1 market share (HDD 47% market share 2024年Q4・Seagate 33% / Toshiba 20% vs Top position) + Enterprise SSD Top 5 vendor・SanDisk 2016年$19B買収 + Western Digital + SanDisk NAND business unified strategy・Kioxia (元東芝Memory) Joint-Venture NAND manufacturing partnership 2000年代以来継続) が発表したCapacity-tier Enterprise NVMe SSD・PCIe Gen 4 x4 (PCIe Gen 5 ではなく Gen 4 Standard・Cost-effectiveness focus + Capacity-tier workload Gen 4 sufficient performance) + 12,000 MB/s Sequential Read (PCIe Gen 4 theoretical limit 8 GB/s actual 12,000 MB/s = Gen 4 dual-port equivalent + Throughput acceleration with on-controller optimization) / 5,300 MB/s Sequential Write + 1,800,000 IOPS Random Read + 3D BiCS5 TLC NAND (112-layer・Kioxia/Western Digital Joint-Venture BiCS5 NAND・前世代BiCS4 96-layer から Layer count increase) + 1.92TB-15.36TB capacity options + U.2 (2.5" 15mm) + EDSFF (E1.S / E3.S) Multi form factor + Capacity-tier specialized (Read-intensive Capacity workload optimized 1 DWPD・Cold Storage / Capacity warehousing focus) ・$0.10-$0.13/GB Mid-Premium Capacity tier (Micron 7500 $0.10-$0.15/GB vs $0.02-$0.05 cheaper・Cost-effective Capacity Enterprise NVMe)・Western Digital HDD Number 1 brand + SanDisk NAND integration + Kioxia BiCS Joint-Venture heritage の Capacity-tier Enterprise NVMe (Hyperscale Performance-tier ではなく Capacity-tier specialization)。
主な特徴・仕組み
- Interface: PCIe Gen 4 x4 (16 GT/s lane × 4 = 64 GT/s total bidirectional・Gen 5 ではなく Gen 4 standard)
- NAND: BiCS5 TLC NAND (112-layer・Kioxia/Western Digital Joint-Venture)
- Sequential Read: 12,000 MB/s (PCIe Gen 4 dual-port equivalent + Controller optimization)
- Sequential Write: 5,300 MB/s
- Random Read: 1,800,000 IOPS (1.8M IOPS)
- Random Write: 280,000 IOPS
- Capacity Options: 1.92TB / 3.84TB / 7.68TB / 15.36TB
- Endurance: 1 DWPD (Read-intensive Capacity-tier・Capacity warehousing focus)
- Form Factor: U.2 (2.5" 15mm) + E1.S (EDSFF) + E3.S (EDSFF Premium)
- Power: 10-18W TDP (Lower power due Gen 4 + Capacity-tier)
- Encryption: AES-256 (FIPS 140-3 Level 2 + TCG OPAL 2.0)
- MTBF: 2,500,000 hours
- Workload: Capacity-tier (Cold storage / Capacity warehousing / Read-intensive less-active data)
- Price: $0.10-$0.13/GB (Mid-Premium Capacity tier・Lower than Hyperscale Performance tier)
スペック比較表
| Enterprise NVMe SSD Capacity vs Performance tier (2024) | Interface | Tier | Read | Endurance | Price |
|---|---|---|---|---|---|
| WD Ultrastar DC SN655 | PCIe Gen 4 | Capacity-tier | 12,000 MB/s | 1 DWPD | $0.10-$0.13/GB |
| Micron 7500 | PCIe Gen 5 | Mid-Premium | 13,300 MB/s | 1-3 DWPD | $0.10-$0.15/GB |
| Kioxia CM7-R | PCIe Gen 5 | Hyperscale | 14,000 MB/s | 1 DWPD | $0.15-$0.20/GB |
| Samsung PM1745 | PCIe Gen 5 | Hyperscale | 14,800 MB/s | 3 DWPD | $0.15-$0.20/GB |
| Micron 9550 | PCIe Gen 5 | Hyperscale Top | 14,000 MB/s | 3 DWPD | $0.15-$0.20/GB |
具体例・対応製品
- WD Ultrastar DC SN655 1.92TB / 3.84TB / 7.68TB / 15.36TB: 4 capacity options
- WD Ultrastar DC SN840 (前世代・Mixed-use・2022年): $0.12-$0.16/GB・3 DWPD + Higher performance
- WD Ultrastar DC HC580 (HDD Capacity-tier・Compare reference): 30TB HDD $0.02/GB Cold tier (NVMe SN655 vs HDD Cost ratio 5-6x差)
- WD SanDisk SkyHawk AI (Consumer/SOHO・Surveillance): $0.05-$0.08/GB Consumer + Surveillance focus
- 競合 Solidigm D7-PS1010: $0.14-$0.18/GB・PCIe Gen 5 + Hyperscale tier (Higher performance + Higher price)
自作PCでの選び方・注意点
Western Digital Ultrastar DC SN655 は「Capacity warehousing (Cold storage / Read-intensive less-active data tier)」「Cost-effective Enterprise NVMe (PCIe Gen 4 standard + $0.10-$0.13/GB)」「Hyperscaler Capacity-tier (Hot Performance tier $0.15-$0.20/GB vs $0.05+/GB cheaper)」用途のCapacity-tier Enterprise NVMe SSD。Consumer / 自作PC範囲外・Server / Storage Array deployment専用・PCIe Gen 4 standard (Performance Gen 5 ではなく Cost-effectiveness focus) で Capacity workload Gen 4十分performance + Cost reduction $0.05+/GB cheaper (Hyperscale Performance tier $0.15-$0.20/GB vs $0.10-$0.13/GB)・Capacity warehousing use case (Cold storage / Read-intensive less-active data / Tier-2 capacity) で Cost-effective + Capacity scale-out economical positioning。Western Digital HDD Number 1 share (47%) + SanDisk NAND integration + Kioxia BiCS Joint-Venture heritage + Long-term Enterprise Storage Customer relationship + Multi-form factor support (U.2 + E1.S + E3.S) で Customer Server configuration flexibility・Capacity-tier specialization position (Hyperscaler / Cloud Provider Capacity warehouse use case best fit) + Performance tier (Hyperscale workload) は Micron 9550 / Samsung PM1745 / Kioxia CM7-R / Solidigm D7-PS1010 等 PCIe Gen 5 vendors選択肢推奨。BiCS5 112-layer NAND (前世代BiCS4 96-layer から Layer count increase but Industry-leading 236-layer Samsung V8 / 232-layer Micron / 218-layer Kioxia CM7-R vs lower layer count = Storage density劣勢) で Cost-effective Lower-tier NAND positioning。
関連用語との違い
- vs Micron 7500: WDはPCIe Gen 4 + Capacity-tier + 112-layer・MicronはPCIe Gen 5 + Mid-Premium + 232-layer + Higher performance
- vs Hyperscale tier Kioxia CM7-R / Samsung PM1745 / Micron 9550: WDはCapacity-tier $0.10-$0.13・HyperscaleはPerformance tier $0.15-$0.20
- vs WD Ultrastar DC SN840 (前世代Mixed-use): SN655はCapacity-tier + Cost-down・SN840はMixed-use 3 DWPD + Higher performance
よくある質問（FAQ）
Q1: PCIe Gen 4 + Capacity-tier の戦略意義は？ A: Hyperscaler / Cloud Provider Customer base で Hot Performance tier (Active workload・Database OLTP・AI training) と Capacity warehouse tier (Cold storage・Read-intensive less-active data) を分離 + Cost optimization tier-based deployment・WD SN655 = Capacity-tier $0.10-$0.13/GB で Hyperscaler internal cost optimization alignment + PCIe Gen 4 standard で Cost-effective sufficient Performance + Capacity scale-out economical。
Q2: BiCS5 112-layer vs Industry-leading 236-layer 差は？ A: BiCS5 (Kioxia/Western Digital Joint-Venture 2020年世代) 112-layer + 前世代 BiCS4 96-layer から Layer count increase・but Samsung V8 236-layer / Micron 232-layer / Kioxia BiCS8 218-layer 等のNAND Big-3 layer count race中で Lower layer count = Storage density per chip area劣勢・but Cost-effective NAND + Mature production yield + Capacity-tier workload Performance十分。
Q3: Western Digital HDD + SSD integrated strategy は？ A: WD HDD Number 1 brand (47% market share) + SanDisk NAND (2016 $19B買収) + Kioxia BiCS Joint-Venture (2000年代以来) で Enterprise Storage Multi-product portfolio (HDD + SSD) + Customer Long-term Storage Strategic relationship + Tier-based deployment optimization (HDD Cold tier + SSD Capacity tier + SSD Performance tier hierarchy) で Total Storage cost optimization。
まとめ
WD Ultrastar DC SN655 = 2024年Western Digital発表のCapacity-tier Enterprise NVMe SSD。PCIe Gen 4 + BiCS5 112-layer + 12,000 MB/s + Capacity-tier 1 DWPD + $0.10-$0.13/GB・WD HDD Number 1 brand + SanDisk NAND integration + Kioxia BiCS Joint-Venture heritage + Capacity-tier Enterprise NVMe specialization Cost-effective tier。