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FStree doc improvements #3033

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Nov 29, 2024
Merged

FStree doc improvements #3033

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28a224b
fstree: comment typo fix
roman-khimov Nov 28, 2024
11f083c
docs: add a bit more notes for FSTree
roman-khimov Nov 28, 2024
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16 changes: 13 additions & 3 deletions docs/storage-node-configuration.md
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Expand Up @@ -203,13 +203,23 @@ blobstor:
| `flush_interval` | `duration` | `10ms` | Time interval between batch writes to disk. |

#### `fstree` type options
FSTree stores objects using file system provided by OS. It uses a hierarchy of
directories (tree) based on object ID, directory nesting level is controlled by
depth. To optimize writing performance for small object it can also combine
multiple objects into a single file, this behavior can be controlled as well.

The default FSTree settings are optimized for HDD and small files. In case of
deploying to SSD combined writer is recommended to be disabled completely
(combined_count_limit=1). For medium/large files or smaller drives depth is
recommended to be adjusted to 3 or even lower values. Larger values are only
relevant for big volumes with very high number of stored objects.
| Parameter | Type | Default value | Description |
|---------------------------|-----------|---------------|------------------------------------------------------------------------------------------------------------------------------|
| `path` | `string` | | Path to the root of the blobstor. |
| `perm` | file mode | `0640` | Default permission for created files and directories. |
| `depth` | `int` | `4` | File-system tree depth. |
| `no_sync` | `bool` | `false` | Disable write synchronization, makes writes faster, but can lead to data loss. |
| `combined_count_limit` | `int` | `128` | Maximum number of objects to write into a single file, 0 or 1 disables combined writing (disabling is recommended for SSDs). |
| `depth` | `int` | `4` | File-system tree depth. Optimal value depends on the number of objects stored in this shard, the number of lower-level directories used by FSTree is 58^depth, with depth 3 this is ~200K, with 4 --- ~11M |
| `no_sync` | `bool` | `false` | Disable write synchronization, makes writes faster, but can lead to data loss. Not recommended for production use. |
| `combined_count_limit` | `int` | `128` | Maximum number of objects to write into a single file, 0 or 1 disables combined writing (which is recommended for SSDs). |
| `combined_size_limit` | `size` | `8M` | Maximum size of a multi-object file. |
| `combined_size_threshold` | `size` | `128K` | Minimum size of object that won't be combined with others when writing to disk. |

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2 changes: 1 addition & 1 deletion pkg/local_object_storage/blobstor/fstree/fstree.go
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Expand Up @@ -71,7 +71,7 @@ const (
// different.
combinedPrefix = 0x7f

// combinedLenSize is sizeof(uint32), length is a serialized 32-bit BE integer.
// combinedLenSize is sizeof(uint32), length of a serialized 32-bit BE integer.
combinedLenSize = 4

// combinedIDOff is the offset from the start of the combined prefix to OID.
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