A B-tree updates a page where the row lives, which means a random-key write pattern turns into a random-page write pattern. An LSM tree refuses that trade: it appends, and rewrites in bulk later. Everything else about the design — the memtable, the bloom filters, the compaction policy — follows from that one refusal. ...
A sparse regular file can have a large logical length while allocating storage for only part of its address range. Reads from holes within that length return zero bytes. File length, byte content, and filesystem allocation are therefore different measurements. Understanding their relationship matters when budgeting virtual disks, copying backups, or deciding whether a zero-filled region actually reserves space for future writes. ...
A container is ephemeral by design, so a PersistentVolumeClaim is the handle that pins real storage to it even when the Pod is recreated. The split is deliberate: a PersistentVolume declares capacity that exists, a PersistentVolumeClaim requests capacity that is needed, and a controller matches one to the other. With a StorageClass the claim can create its own volume through a provisioner, so nobody has to pre-build the storage. ...
An NFS export is a directory on the server plus a list of clients allowed to reach it; the file that describes it is not what serves it. /etc/exports is read by exportfs, which writes the master export table to /var/lib/nfs/etab, which rpc.mountd consults on a client’s MOUNT request. Three files: one that people edit, two that decide what happens. ...
RDB and AOF preserve different representations of Redis state. Choosing between them starts with two questions: how much recent data may be lost, and how long recovery may take? A persistence setting alone answers neither. You need a recoverable artifact, an understood acknowledgment policy, and a restore procedure tested against actual values. ...
An unlogged PostgreSQL table keeps normal SQL transaction behavior while giving up crash recovery for its contents. It is useful for reproducible staging data, but a committed row is not guaranteed to survive a server crash. The distinction is between clean operation and recovery after an unclean shutdown, not between ordinary queries and every restart. ...
Versioning turns an overwrite and a delete into appends. Instead of replacing bytes, a versioned bucket mints a new version ID and keeps the old one, so a mistaken PUT or a mistaken DELETE is reversible. That is genuine cheap disaster recovery for anything you manage through the bucket rather than through a database. ...
A Redis bitmap is a string interpreted as individual bits, not a separate key type. It is useful for dense yes/no membership such as daily activity. Ten million contiguous flags need 1,250,000 payload bytes, but that estimate excludes keys, object metadata, allocation overhead, and any mapping from business identifiers to bit positions. ...