From Pure Storage FlashArray to Ceph

Pure Storage FlashArray is a polished, low-effort all-flash SAN, but it is a proprietary appliance with subscription/support costs and a hardware refresh cycle you don’t fully control. Ceph is the open-source, software-defined alternative: a distributed cluster that provides block (RBD), file (CephFS), and object (RGW) storage on commodity servers, with no per-array license. This is the biggest mindset change of any migration in this category, because you are not swapping one array for another, you are replacing a turnkey appliance with a distributed system you design, size, and operate. Respect that, and Ceph is excellent; underestimate it, and it will punish you.

The mindset shift: appliance → cluster

FlashArray hides complexity: you carve volumes, present them over iSCSI/FC/NVMe, and Pure handles data placement, redundancy, and dedup behind a simple UI. Ceph exposes the building blocks:

• OSDs (one per disk) store the data; you need enough across enough nodes for your chosen redundancy.
• Replication (3×) or erasure coding is your durability choice, and it directly sets your usable-vs-raw ratio and performance.
• CRUSH maps control placement across hosts/racks for failure-domain isolation.
• MON/MGR nodes run the control plane.

A safe Ceph cluster wants a minimum of three (ideally five) nodes and a fast, dedicated network. If you size it like a single appliance, you’ll be disappointed; size it like a distributed system and it scales further than the array ever could.

Shifting the data across

There is no array-to-array magic between Pure and Ceph; data moves at the host or hypervisor level:

1. Provision Ceph pools, RBD pools for block workloads, CephFS for shared file, sized with your replication/EC choice.
2. Present new storage to the consumers, map RBD images (or iSCSI via the Ceph iSCSI gateway) to hosts, or mount CephFS.
3. Move the data with host-level tools, rsync for file data, storage vMotion/live storage migration for VMs (let the hypervisor copy guests from Pure LUNs onto Ceph RBD), or application-native replication for databases.
4. Cut over per workload and validate before reclaiming the Pure volume.

Migrating at the hypervisor/host layer means you can move workload by workload with minimal downtime, rather than attempting a risky bulk array copy.

Re-presenting LUNs, then checking the tail latency

Re-presentation is straightforward once the pools exist, but the details decide whether rollback stays easy. Each FlashArray volume maps to one RBD image. RBD-aware consumers (KVM/QEMU, OpenStack, Kubernetes CSI) attach the image natively; hosts that still expect a SAN LUN reach it through the Ceph iSCSI gateway, where you recreate the target, the initiator groups (reusing the same host IQNs), and the LUN mapping. Keep the mapping one-to-one and leave the Pure volume intact but unmapped until the Ceph copy is verified in production, so a rollback is a single re-present rather than a rebuild.

Then validate before you reclaim anything. Capture the FlashArray baseline first: IOPS, throughput, and latency at the queue depths your workloads actually run. Replay that profile against the Ceph pool and compare the 99th-percentile latency under load, because FlashArray’s strength is consistency, and an average that looks fine can hide tail latency that a latency-sensitive application will feel. Run part of that test while a simulated OSD failure is rebalancing, since rebuild traffic is exactly when Ceph latency degrades. Only once the numbers hold, and a snapshot or RBD-mirroring DR test passes, should you release the Pure volume.

Performance and operational realities

• Latency profile differs. FlashArray delivers very consistent low latency from purpose-built hardware. Ceph latency depends on your media (use NVMe/SSD OSDs, never spinning disks for latency-sensitive block), network (10/25GbE+ minimum, separate public/cluster networks), and tuning. Benchmark your workload on the cluster before cutover, don’t trust generic numbers.
• Redundancy costs capacity. 3× replication means usable ≈ raw/3; erasure coding recovers space at a CPU/latency cost. Plan raw capacity accordingly.
• Operations are yours. Upgrades, rebalancing, failed-disk replacement, and capacity planning are now your team’s job (cephadm/Rook make this far easier than it used to be, but it’s still real work). Factor that engineering time into the comparison.

Where Pure still wins, don’t over-migrate

If your priority is predictable low latency with near-zero storage-admin overhead, a small footprint, or features like Pure’s effortless dedup/compression and support SLAs, the appliance may still be the better total-cost answer for that tier. Ceph’s economics come good at scale and where you have (or want to build) the operational capability. Move the bulk/general-purpose and growth workloads to Ceph; keep Pure for the latency-critical tier if the math favours it there.

Making the call

Pure FlashArray → Ceph removes appliance licensing and refresh lock-in, but you take on running a distributed storage system. Size the cluster properly (3–5+ nodes, fast dedicated network, flash OSDs), migrate workload by workload at the host/hypervisor layer, and benchmark your real latency before cutting over. Account for replication overhead and the operational time Ceph needs, and keep Pure for any truly latency-critical tier. Model the removed array subscription against cluster hardware and ops time in the calculator above.