Where would the disk details for SAN and NAS devices be held in the ServiceNow CMDB

[nareshTT]

Hello Friends,

I have a query (kind of confusion) about 2 tables. If I would like to discover SAN and NAS devices, in which table disk details would be stored ? I came across 2 tables i.e. cmdb_ci_san_disk in case of SAN device and another one is cmdb_ci_storage_device. 

Could you please help me out to understand where exactly disk details would be held for SAN and NAS devices  ?

Thanks,

Amit

[Maik Skoddow · Accepted solution]

Hi @nareshTT 

Okay, let's break down where disk details for SAN and NAS devices are typically stored in the ServiceNow CMDB. You've hit on the key complexity: the distinction between physical disks, logical units (LUNs), volumes, and file shares.

1. cmdb_ci_storage_device(Storage Device):

   • Purpose: This table is generally intended to represent physical disk drives (HDDs, SSDs).
   • Context: These CIs are often discovered within a host (server) or potentially within a storage array (SAN/NAS) if ServiceNow Discovery has the credentials and probes/patterns capable of interrogating the array's hardware components directly.
   • Relevance to SAN/NAS:
     • Physical Disks Inside the Array: If Discovery can identify the individual physical drives within a SAN array or NAS filer, they would likely be populated in this table, related back to the main CI for the array/filer (e.g., cmdb_ci_storage_server or cmdb_ci_nas_filer). However, discovering individual physical disks inside enterprise storage arrays is often less common or requires specific vendor integrations/probes.
     • Direct Attached Storage (DAS) in Servers: This table is very commonly used for disks directly attached to or inside discovered servers.

2. cmdb_ci_san_disk(SAN Disk - Often Represents LUNs):

   • Purpose: Despite the name "disk", this table is often used to represent Logical Unit Numbers (LUNs) presented by a SAN storage array to consuming hosts. It represents the logical block storage unit made available over the SAN fabric, not necessarily the physical disk(s) backing it.
   • Context: SAN Discovery typically finds SAN switches, fabrics, zones, storage arrays, and the LUNs they present.
   • Relevance to SAN: This is a primary table for representing the logical storage volumes (LUNs) provisioned from a SAN array and made accessible to servers via Fibre Channel or iSCSI. It will often have relationships to the Storage Array CI (cmdb_ci_storage_server), the presenting ports (cmdb_ci_fc_port, cmdb_ci_iscsi_interface), and potentially the consuming server.
   • Relationship to cmdb_ci_storage_volume: Often, a cmdb_ci_san_disk CI might be conceptually similar or directly related to a cmdb_ci_storage_volume CI. The cmdb_ci_storage_volume table is a more general representation of logical storage volumes that can apply to SAN LUNs, server logical volumes (LVM), etc. The specific implementation might vary slightly depending on the Discovery patterns used.

Where NAS "Disk" Details Fit:

• NAS Filers Themselves: The NAS device itself is typically represented by a CI in cmdb_ci_nas_filer or sometimes a more generic server class depending on the device/OS.
• Physical Disks (Less Common): As mentioned for SAN, if Discovery can probe the NAS appliance deeply enough, the physical disks inside it might appear as cmdb_ci_storage_device CIs related to the NAS Filer CI.
• File Shares (Primary Focus): NAS is primarily about file-level access. Discovery focuses on identifying the shares presented by the NAS device. These are stored in tables like:
  • cmdb_ci_nfs_export (for NFS shares)
  • cmdb_ci_cifs_share (for CIFS/SMB shares)
• Logical Volumes/Pools: Many NAS devices also manage storage internally using logical volumes or pools before creating shares on top. If discoverable, these might be represented in cmdb_ci_storage_volume or cmdb_ci_storage_pool, related to the NAS Filer CI.

Summary Table:

Concept	Most Likely ServiceNow Table(s)	Notes
Physical Disk Drive	cmdb_ci_storage_device	Inside servers (common) or storage arrays (less common/requires specific probes).
SAN Logical Unit (LUN)	cmdb_ci_san_disk, cmdb_ci_storage_volume	Represents the logical block volume presented by the SAN array. cmdb_ci_san_disk is SAN-specific.
NAS File Share	cmdb_ci_nfs_export, cmdb_ci_cifs_share	Represents the accessible file share over the network.
Storage Array (SAN/NAS)	cmdb_ci_storage_server, cmdb_ci_nas_filer	Represents the overall storage appliance.
Storage Pool (Internal)	cmdb_ci_storage_pool	Represents aggregates of storage within an array from which volumes/LUNs are created.
Logical Volume (General)	cmdb_ci_storage_volume	Represents logical volumes on servers or potentially within arrays.

Conclusion:

• For physical disk drives (if discoverable within the array or attached to a host consuming storage), look primarily in cmdb_ci_storage_device.
• For SAN LUNs (the logical units presented by the SAN), look primarily in cmdb_ci_san_disk and potentially cmdb_ci_storage_volume.
• For NAS, the focus is usually on the filer itself (cmdb_ci_nas_filer) and the shares (cmdb_ci_nfs_export, cmdb_ci_cifs_share). Associated logical volumes might be in cmdb_ci_storage_volume, and underlying physical disks (if found) in cmdb_ci_storage_device.

Maik

[smridh]

HI @Maik Skoddow ,

Appreciate your effort explaining DAS, SAN and NAS.
I am not able to find the table "cmdb_ci_nas_filer". Can you confirm if the above-mentioned table is correct?

Thanks,
Smridh Makkar