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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

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Inputs

InputSourceUsed For
Number of protected workloadsCompute inventoryStorage and throughput
Average workload sizeDisk usage per workloadInitial full size estimate
Average daily change rateWorkload telemetryIncremental size estimate
Retention windowsCompliance policyTotal retained generations
Deduplication ratioPilot measurementCompression of storage estimate
Compression ratioPilot measurementCompression of storage estimate
Backup window durationOperational policyConcurrent throughput target
Restore RTORecovery objectiveRead throughput target

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Storage Sizing

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

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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
LayerSnapshotsRaw BytesAfter Dedup + Compression
Daily incremental (200 × 7 × 2 GB)1,4002,800 GB224 GB
Weekly full (200 × 3 × 100 GB)60060,000 GB4,800 GB
Total Primary DC datastore62,800 GB~5,000 GB
Add 30% headroom for unexpected growth, deduplication misses, and metadata. Provision ~6.5 TB for Primary DC datastore.

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Reference Calculation — Backup Site

Backup site holds 52 weeks of weekly fulls. Assumptions same as above plus retention keep-weekly=52.
LayerSnapshotsRaw BytesAfter Dedup + Compression
Weekly full archival (200 × 52 × 100 GB)10,4001,040,000 GB83,200 GB
Total Backup site datastore1,040,000 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.

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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.
ScenarioRehydration Capacity Required
Restore single workload (largest)1 × largest workload size
Restore 10% of workloads simultaneously20 × 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.

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Throughput Sizing

Throughput drives both backup window duration and restore RTO.

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Backup Throughput

Backup ingest rate = (Σ incremental change bytes per day) ÷ backup window seconds
For the reference example:
SettingValue
Total incremental per day200 × 2 GB = 400 GB
Backup window4 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.

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Restore Throughput

Restore RTO = workload size ÷ restore throughput
Workload SizeRestore ThroughputRTO
100 GB200 MB/s~8 minutes
500 GB200 MB/s~42 minutes
1 TB200 MB/s~85 minutes
5 TB200 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.

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Backup Server Compute Sizing

ResourcePer Backup ServerNotes
CPU8-16 coresHeavy compression and verification load
RAM32-64 GBChunk cache improves dedup hit rate
Datastore diskSized per storage calculationSSD or hybrid for primary; HDD or object for archival
Local OS disk200 GB SSDOS, logs, configuration
Network10 GbE minimumBoth ingest and replication
For very large environments, scale horizontally — multiple backup servers each owning a partition of the datastore namespace.

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Network Sizing

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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.

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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:
SettingValue
Weekly full snapshots per week200
Per-snapshot size (after dedup + compression)~8 GB
Total weekly archival1,600 GB
Sync window6 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.

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Sizing Worksheet

Use this worksheet to derive a custom sizing.
InputYour 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

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Reference Sizing Table

Fleet SizePrimary DCBackup SiteInter-site
50 workloads, 100 GB avg1.5 TB25 TB250 Mbps
200 workloads, 100 GB avg6.5 TB110 TB1 Gbps
500 workloads, 200 GB avg32 TB540 TB5 Gbps
1,000 workloads, 500 GB avg160 TB2.7 PB25 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.

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Growth Planning

MetricSourceAction
Datastore fill rate (GB/week)Datastore statistics panelProject fill date; expand at 70% used
Inter-site sync durationSync job historyExpand bandwidth or shorten retention if duration grows
Restore time trendsRestore task historyTune live-restore usage or storage tier
Verification job durationVerification task historyExpand 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.

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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.

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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