---
title: "Limits"
slug: "dev-datastore-reference-limits"
updated: 2026-10-28T02:15:03Z
published: 2026-10-28T02:15:03Z
canonical: "docs.vastdata.com/dev-datastore-reference-limits"
---

> ## Documentation Index
> Fetch the complete documentation index at: https://docs.vastdata.com/llms.txt
> Use this file to discover all available pages before exploring further.

# Limits

*Applies to VAST Cluster 5.5.*

Sizes and counts for S3, NFS and multiprotocol use on VAST Cluster 5.5. Where the cluster is more permissive than AWS S3 (part size, object size), the table says so; keep to the AWS limits anyway if your code also runs against other S3 stores.

## S3

| Item | Limit | Notes |
| --- | --- | --- |
| Bucket name | 3–63 characters | Lowercase letters, digits, hyphens and dots, DNS-style; other names get `400 InvalidBucketName`. Unique across the cluster. |
| Object key | 1,024 characters, at most 198 `/` | Longer keys get `400 KeyTooLong`, more slashes `400 InvalidArgument`. |
| One part of a key (between slashes) | 255 characters by default | It's a file or directory name ([NFS and file names](/develop/docs/dev-datastore-reference-limits#nfs-and-file-names)); longer parts get `400 InvalidObjectName`. |
| Tags per object | 40 | 41 get `400 MalformedXML`. Keys unique per object, case-sensitive. |
| Tag key / value | 128 / 256 characters, ASCII | Longer keys or values, and any non-ASCII character, get `400 InvalidTag` with the message `Cannot provide multiple Tags with the same key`. A `+` set with `PutObjectTagging` is stored as a space: avoid it. |
| User metadata per object | 2 KB (2,048 bytes, keys and values together) | One byte more gets `400 MetadataTooLarge`. |
| Keys per listing call | 1,000 | A larger `MaxKeys` still returns 1,000. Use pagination for more. |
| Bucket policy | 20 KB (20,480 bytes), one per bucket | One byte more gets `400 InvalidPolicyDocument`. |
| Session policy (STS) | 2,048 characters | One more gets `400 PackedPolicyTooLarge`. |
| Temporary credentials (STS) | 15 minutes to 36 hours | Capped by the role's maximum session duration: a longer request gets `400 ValidationError` (`request duration exceeds role's MaxSessionDuration`). |
| Presigned POST policy | 4,800 bytes, counted on the request rather than the JSON | A policy of 3,450 bytes of JSON (4,600 bytes base64-encoded, as it's sent) was accepted, and one of 3,488 bytes (4,652 encoded) was refused with `400 InvalidRequest`. Keep the encoded policy well under 4,800 bytes. Object names must be ASCII. |
| Access key / secret key you supply | 21 / 41 characters | When your platform team creates a key pair from strings you provide. |
| Lifecycle rule | 15 MB | Admin-set rules. |
| Part numbers in a multipart upload | 1 to 10,000 | Other numbers get `400 InvalidPart`. |
| Part size | No minimum or 5 GiB maximum enforced | Parts of one byte, and a part of 5 GiB + 1 byte, were accepted. AWS requires 5 MiB to 5 GiB (except the last part); many clients enforce that. |
| Single `PutObject` | No 5 GiB maximum enforced | 5 GiB + 1 byte was accepted. The maximum object size isn't stated. |

## NFS and file names

| Item | Limit | Notes |
| --- | --- | --- |
| File or directory name (one path component) | 255 characters by default | A longer name fails with `File name too long`. A view policy can switch to each protocol's native limit ("Native Protocol Limit"). Files that use the longer names may then be unreachable over other protocols. |
| Characters in names | Those allowed by all supported protocols, by default | Also relaxable per view policy. |
| `nconnect` connections to one VIP | 16 |  |
| Byte-range locks per file | Depends on the length of the lock holders' host names | As a rough guideline, about 100,000 locks per file with 40-character host names. |
| Extended attribute name / value (NFSv4.2) | 128 / 256 characters by default | Larger with the native name-length setting; ask your platform team for the values that apply. |
| Extended attributes per file | No cluster limit | Some clients limit how many they can list. |

## VAST Catalog

If you find files and objects through the VAST Catalog, it supports paths up to 1,024 characters. See the [Catalog overview](/develop/docs/dev-catalog-overview).

## See also

- [S3 compatibility](/develop/docs/dev-datastore-reference-s3-compatibility) and the [NFS reference](/develop/docs/dev-datastore-reference-nfs).