Infrastructure Sizing

Overview

Sizing Ironcore Backup Solution (IBS) infrastructure is a balance of retention windows, deduplication efficiency, network capacity, and recovery objectives. This page provides reference sizing for the standard compliance retention pattern (7-day daily, 3-week weekly at Primary DC; 52-week weekly at Backup site) plus guidance for adjusting upward or downward.

Prerequisites

Administrator role on the Polystack platform
Knowledge of workload count, daily change rate, and average workload size
Inter-site bandwidth between Primary DC and Backup site

Inputs

Input	Source	Used For
Number of protected workloads	Compute inventory	Storage and throughput
Average workload size	Disk usage per workload	Initial full size estimate
Average daily change rate	Workload telemetry	Incremental size estimate
Retention windows	Compliance policy	Total retained generations
Deduplication ratio	Pilot measurement	Compression of storage estimate
Compression ratio	Pilot measurement	Compression of storage estimate
Backup window duration	Operational policy	Concurrent throughput target
Restore RTO	Recovery objective	Read throughput target

Storage Sizing

The fundamental formula:

Stored bytes = (Σ full snapshots × workload size + Σ incremental snapshots × change size)
               ÷ (dedup ratio × compression ratio)

Reference Calculation — Primary DC

Assumptions:

200 protected workloads
Average workload size: 100 GB
Average daily change rate: 2% (2 GB/day per workload)
Deduplication ratio: 5x (typical mixed workloads)
Compression ratio: 2.5x (typical mixed workloads)
Retention: keep-daily=7, keep-weekly=3

Layer	Snapshots	Raw Bytes	After Dedup + Compression
Daily incremental (200 × 7 × 2 GB)	1,400	2,800 GB	224 GB
Weekly full (200 × 3 × 100 GB)	600	60,000 GB	4,800 GB
Total Primary DC datastore		62,800 GB	~5,000 GB

Add 30% headroom for unexpected growth, deduplication misses, and metadata. Provision ~6.5 TB for Primary DC datastore.

Reference Calculation — Backup Site

Backup site holds 52 weeks of weekly fulls. Assumptions same as above plus retention keep-weekly=52.

Layer	Snapshots	Raw Bytes	After Dedup + Compression
Weekly full archival (200 × 52 × 100 GB)	10,400	1,040,000 GB	83,200 GB
Total Backup site datastore		1,040,000 GB	~83 TB

Add 30% headroom. Provision ~110 TB for Backup site datastore. Add rehydration capacity for restoring archived data during recovery — see the next section.

Deduplication ratio increases substantially when multiple workloads share an OS image, runtime, or dataset. Production environments often exceed 5x. Measure on a pilot before sizing — typical observed range is 3x to 8x.

Rehydration Capacity at the Backup Site

During recovery, archived data is rehydrated to a working datastore at the Backup site for compute access. Plan rehydration capacity for the largest single workload to be restored.

Scenario	Rehydration Capacity Required
Restore single workload (largest)	1 × largest workload size
Restore 10% of workloads simultaneously	20 × average workload size
Restore all workloads (disaster)	All workloads (potentially partial via live-restore)

Typical practice: provision rehydration capacity for 10% of total workload footprint to support routine restores plus a planned multi-workload drill. For the reference example above: 200 workloads × 100 GB × 10% = 2 TB rehydration capacity.

Use live-restore for the largest workloads — it begins serving the guest OS in seconds, avoiding the need to rehydrate the full disk to local storage before powering on.

Throughput Sizing

Throughput drives both backup window duration and restore RTO.

Backup Throughput

Backup ingest rate = (Σ incremental change bytes per day) ÷ backup window seconds

For the reference example:

Setting	Value
Total incremental per day	200 × 2 GB = 400 GB
Backup window	4 hours (14,400 s)
Required ingest rate	~27 MB/s
With 50% safety margin	~40 MB/s

A single backup server with a modern HDD or SSD datastore comfortably handles this load. For larger fleets (1,000+ workloads), distribute across multiple backup servers each owning a subset of namespaces.

Restore Throughput

Restore RTO = workload size ÷ restore throughput

Workload Size	Restore Throughput	RTO
100 GB	200 MB/s	~8 minutes
500 GB	200 MB/s	~42 minutes
1 TB	200 MB/s	~85 minutes
5 TB	200 MB/s	~7 hours

Live-restore shifts the perceived RTO to seconds for the guest OS, with background restore continuing while the workload is running.

Backup Server Compute Sizing

Resource	Per Backup Server	Notes
CPU	8-16 cores	Heavy compression and verification load
RAM	32-64 GB	Chunk cache improves dedup hit rate
Datastore disk	Sized per storage calculation	SSD or hybrid for primary; HDD or object for archival
Local OS disk	200 GB SSD	OS, logs, configuration
Network	10 GbE minimum	Both ingest and replication

For very large environments, scale horizontally — multiple backup servers each owning a partition of the datastore namespace.

Network Sizing

Within a Site

Backup traffic between workloads and the local backup server is intra-DC, typically over 10 GbE or 25 GbE. The 27 MB/s figure above sits well within either capacity.

Between Sites

Inter-site replication runs over a metro or WAN link. Size for the weekly archival sync.

Inter-site bandwidth = (weekly archival data) ÷ sync window

For the reference example with 200 workloads:

Setting	Value
Weekly full snapshots per week	200
Per-snapshot size (after dedup + compression)	~8 GB
Total weekly archival	1,600 GB
Sync window	6 hours overnight Sunday
Required sustained bandwidth	~75 MB/s
With 50% safety margin	~110 MB/s = ~1 Gbps

For typical enterprises, 1 Gbps dedicated inter-site link is sufficient for the reference example. Use bandwidth throttling on the sync job to coexist with other traffic during business hours.

Sizing Worksheet

Use this worksheet to derive a custom sizing.

Input	Your Value
Number of protected workloads	_________
Average workload size (GB)	_________
Daily change rate (%)	_________
Deduplication ratio	_________
Compression ratio	_________
Retention: keep-daily	_________
Retention: keep-weekly (Primary)	_________
Retention: keep-weekly (Backup)	_________
Backup window (hours)	_________
Inter-site sync window (hours)	_________

Derived:

Daily incremental volume = workloads × workload_size × daily_change_pct
Weekly full volume = workloads × workload_size

Primary DC raw retained =
  (daily_incremental × keep_daily) +
  (weekly_full × keep_weekly_primary)

Backup Site raw retained =
  weekly_full × keep_weekly_backup

Primary DC datastore size =
  Primary_DC_raw × 1.3 ÷ (dedup × compression)

Backup Site datastore size =
  Backup_Site_raw × 1.3 ÷ (dedup × compression)

Inter-site bandwidth =
  (weekly_full × workloads) ÷ sync_window × 1.5

Reference Sizing Table

Fleet Size	Primary DC	Backup Site	Inter-site
50 workloads, 100 GB avg	1.5 TB	25 TB	250 Mbps
200 workloads, 100 GB avg	6.5 TB	110 TB	1 Gbps
500 workloads, 200 GB avg	32 TB	540 TB	5 Gbps
1,000 workloads, 500 GB avg	160 TB	2.7 PB	25 Gbps

Assumes 5x dedup, 2.5x compression, 2% daily change rate, keep-daily=7, keep-weekly=3 at Primary and keep-weekly=52 at Backup site.

Growth Planning

Metric	Source	Action
Datastore fill rate (GB/week)	Datastore statistics panel	Project fill date; expand at 70% used
Inter-site sync duration	Sync job history	Expand bandwidth or shorten retention if duration grows
Restore time trends	Restore task history	Tune live-restore usage or storage tier
Verification job duration	Verification task history	Expand backup server compute or partition datastore

At 80% datastore utilisation, plan immediate expansion. At 95%, IBS refuses new backups to protect data integrity. Free-space alerts at 80% and 90% are configured automatically — confirm they dispatch to your operations notification group.

Multi-Region Topology

For platforms with multiple Primary sites and a shared Backup site: Size the Backup site for the sum of all Primary sites. Deduplication extends across all sources sharing the datastore — workloads that share an OS image at any Primary site contribute only one copy.

Next Steps

Datastores

Provision the sized datastores

Replication and Sync

Configure replication to match the sized inter-site bandwidth

Retention Policies

Adjust retention windows to match the sized capacity

Architecture

Architectural background for the sizing factors

Core Services

Other Services

Overview

Inputs

Storage Sizing

Reference Calculation — Primary DC

Reference Calculation — Backup Site

Rehydration Capacity at the Backup Site

Throughput Sizing

Backup Throughput

Restore Throughput

Backup Server Compute Sizing

Network Sizing

Within a Site

Between Sites

Sizing Worksheet

Reference Sizing Table

Growth Planning

Multi-Region Topology

Next Steps

Datastores

Replication and Sync

Retention Policies

Architecture

​Overview

​Inputs

​Storage Sizing

​Reference Calculation — Primary DC

​Reference Calculation — Backup Site

​Rehydration Capacity at the Backup Site

​Throughput Sizing

​Backup Throughput

​Restore Throughput

​Backup Server Compute Sizing

​Network Sizing

​Within a Site

​Between Sites

​Sizing Worksheet

​Reference Sizing Table

​Growth Planning

​Multi-Region Topology

​Next Steps

Datastores

Replication and Sync

Retention Policies

Architecture

Overview

Inputs

Storage Sizing

Reference Calculation — Primary DC

Reference Calculation — Backup Site

Rehydration Capacity at the Backup Site

Throughput Sizing

Backup Throughput

Restore Throughput

Backup Server Compute Sizing

Network Sizing

Within a Site

Between Sites

Sizing Worksheet

Reference Sizing Table

Growth Planning

Multi-Region Topology

Next Steps