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Aleksei Sviridkin
a2db2aeb8c
A volume server started with -max 0 takes a slot count derived from disk rather than a fixed one, replication 001 spends a slot on each of the two servers per logical volume, and a collection claims COPY_2 volumes whenever it grows. So the bucket ceiling is set by the product of the size limit and COPY_2, and moving either number alone moves it. The mechanism is upstream in MaybeAdjustVolumeMax (weed/storage/store.go) and findVolumeCount (weed/topology/volume_growth.go). Do not divide these out of the nominal PVC size, because the count follows the space the filesystem makes available and not the volume's advertised size: the shipped 10Gi volume PVC was seen to give nine slots per server at the upstream 1000 and 19 at 500, which puts 400 at 23 to 24 by the same division, or eight collections against two. The span is the observation's own, since the free space behind 19 at 500 fits more than one filesystem geometry and those divide differently at 400; eight either way, because a collection that cannot get a whole batch of COPY_2 keeps the volumes it did get and writes into them. The division itself is measured: on a 1 GB image the master reports max as the filesystem's available space over the limit in every run, 25 slots and nine collections at the 40 and 3 that scale to this pair. Two is what the platform's own cozy-backups bucket and a single tenant bucket already use. Past that every S3 PUT to a new bucket times out while the disk still reads as nearly empty, and no COSI object reports anything wrong, because the claim and the access are both granted. 400 and 3 make the budget 1200 MB per collection. Splitting the reduction across both numbers rather than taking it out of the size limit alone keeps the cost off the curve that grows: open descriptors track stored bytes divided by the limit, so a 10 TiB server keeps roughly 52k of them at this limit against 21k upstream, where moving the size limit alone would have put it at 105k. A .dat and an .idx stay open per volume; the .vif beside them is written and closed. The ceiling reached is the same either way. Both figures describe the shipped replicationFactor of 2. The master picks its growth count from the replication the filer asks for, so at 1 and 3 copies it reads COPY_1 and COPY_3 instead and this COPY_2 does not apply; lowering the size limit still raises the ceiling there. The size limit was out of an operator's reach: it lived in the data-plane chart, which is pulled by ExternalArtifact from a component that declares no install section, so a Package-level values override for it is dropped before any merge. The app chart now declares master.volumeSizeLimitMB and sends it on every release, and 400 is set there. The data-plane chart keeps upstream's 1000 as its fallback on purpose. A platform upgrade can re-render that release from its artifact before the parent has sent anything new, and a lower fallback would then reach the master first and drop the limit ahead of an operator's own setting. COPY_2 is sent by nothing and lives in the data-plane chart, so it does land in that window, where a grow costs 3000 MB against the 6000 MB it cost before. The app chart also writes maxVolumes into dataDirs on every release, and because dataDirs is a list Helm replaces the data-plane chart's copy wholesale, so the zero that makes the slot count auto-derived at all comes from there. Losing it drops the server to the subchart's fixed seven without failing any render. The field is bounded at both ends, because either end takes an instance down. Zero is not a smaller limit but an off switch: the volume server leaves its slot calculation untouched at zero, keeps reporting no capacity, and nothing is ever grown. Past 30000 the master does not start at all. The bound sits in the values schema rather than in a template guard, so Helm refuses the value before any template runs. The apps API does not: it reads that schema only for defaults, so it accepts a value out of range, and the release then fails to render. An explicit null gets past both bounds, because Helm drops the key before it validates, and would render an empty -volumeSizeLimitMB= that the master exits on at start, measured on the shipped image, so the template requires the value. No bound against the disk goes with it, though the field invites one. A limit at or above the volume's own size does not break an instance: MaybeAdjustVolumeMax floors the slot count at one, measured on 4.31 with a 255 MiB disk against a 1000 MB limit, which reported Max 1 and served a write it then read back. Such a server is capped at a single slot rather than dead, so refusing it at render would be a capacity policy that stops a working release on every reconcile, not only on the upgrade. The field's description carries the relation instead, where the value is chosen. The growth count is deliberately not exposed beside the limit. The master picks which of its four growth counts to apply from the replication the filer requests, and the filer takes that from replicationFactor, so a field wired to COPY_2 would do nothing at 1 or 3 copies while still appearing to be a setting. A knob that is silently inert for two of the three supported values is worse than no knob. Two further prices. A collection absorbs the budget before it needs another grow, so growth requests arrive five times as often as at the upstream pair. A collection also starts with half as many writable volumes, and a volume server takes the writes into each volume one at a time (syncWrite holds that volume's dataFileAccessLock), so a heavily parallel writer spreads over fewer volumes until the collection grows again; that holds for instances kept at 1000 too. And lowering the limit on an instance that already holds data carries the other one: its volumes between the new limit and the old go oversized on the next heartbeat and leave the master's writable set, and each affected collection needs one successful grow before its next write lands. Nothing is lost and the volumes stay readable; the room left inside them for further writes is given up and does not return as capacity. Those grows compete for one pool, and the pool is smaller than it looks. An oversized volume is charged no headroom, while one below the limit is charged all of its unfilled room; a grow then claims a whole COPY_2 batch and takes as much of it as is there, and the volumes it creates are empty and charge their headroom straight back. Measured on a local SeaweedFS 4.31 setup: two oversized collections with two free slots between them, the first to write took both, and the second stayed refused with the disk still reporting a quarter of itself free. Collections that need no grow are not free either, since their volumes below the new limit were created six at a time and each can hold back a whole limit. Also measured there, with the limit and batch scaled down: a server with free space for one batch per collection refused the grow its one affected collection needed, because a second, nearly empty collection held the room, and the same free space without it let the grow through. The minFreeSpacePercent reserve only comes into it on a server whose writable volumes have all passed the limit, where nothing is charged headroom: from 8000 MiB of filesystem upward, a 10Gi PVC measuring 9979, five percent is at least 400 MB, and such a server then refuses a grow only once its disk is down to the reserve. Everywhere else the headroom charge decides, and a refusal can arrive with the disk far from full whatever the reserve. Deleting a collection gives the room back a slot per volume, however little it stored, since the headroom charged to those volumes leaves with them. So, on a variant that runs platform migrations, the upgrade does not change the limit on an existing instance unless its operator already set one, which the previous chart accepted and ignored. Platform migration 57 writes master.volumeSizeLimitMB: 1000 into every existing SeaweedFS instance that has not chosen a limit, and 400 applies only to instances created from here on. It leaves alone only an instance whose master is not an object, which no v1 chart renders, and names that one in its log. The default variant runs no platform migrations, so a cluster there that installed SeaweedFS by hand gets no pin, and the document below gives the same patch to apply before upgrading. A chosen limit is a whole number the new chart accepts; anything else counts as not chosen and is replaced with 1000, which is what the previous chart ran in its place, since it ignored the key and the new chart would refuse to render it. A valid value already set is kept, and since the previous chart ignored it, the upgrade is when it starts to apply; the document below lists the ones that change the limit ahead of it. Raised values are listed as well: existing buckets keep writing, but every volume below the new limit is charged up to it, and on a local SeaweedFS 4.31 setup seven nearly empty volumes left no free slot once the limit went up tenfold, so a new bucket was refused. The value goes into the application's HelmRelease, whose spec.values is the application spec, for an instance created through the API and for one the tenant module renders alike. The tenant module never renders spec.values on that release, and a Helm upgrade leaves a key alone that neither manifest carries: measured with Helm 4.3.0 on client-side, server-side and forced server-side apply, and read in createPatch at the v4.1.1 that helm-controller v1.5.0 runs. Where the migration runs, it is a pre-upgrade hook of the platform release, and the cozystack-packages source every application chart comes from is a manifest of that same release, applied only after its hooks; so no instance meets the new chart unstamped, and a failed migration stops the platform upgrade before that source moves. That holds while the platform source is pinned by digest, as it is out of the box; one that follows a tag, a semver range or a branch lets source-controller move cozystack-packages on its own schedule. Until cozystack-packages moves, each patched release keeps its old chart, which ignores the key, since no v1 release reads it or closes the master object in its schema. An instance kept at 1000 still gains, because at a replication factor of 2 a grow now claims three volumes rather than six, so it has room for roughly twice as many new buckets. Lowering an existing instance is left to its operator, and docs/operations/seaweedfs-lowering-the-volume-size-limit.md is the check for it. It lists each server's volume files and adds one limit for every volume below the limit and a batch for every collection with no volume at or below 90 percent of it, since the master grows such a collection on its own schedule without a write; measured the same way, a collection with every volume in that band and no writes got two new volumes per server within one pass. Where each disk type is served by as many volume servers as the replication factor, as the shipped two at a factor of 2 are, each collection's volumes sit on every server of that type, and that bounds the claim from above without assuming how the collections grew. The master places a new volume on any server of the requested disk type with room rather than where its collection already lives, whichever group or pool that server belongs to, and it reads an empty disk type as hdd; under MultiZone it also grows each zone on its own. So the document keeps zoned instances, and any disk type served by more servers than copies, at 1000. BREAKING CHANGE: on the default variant, which runs no platform migrations, set master.volumeSizeLimitMB to 1000 before upgrading on every SeaweedFS instance that has no valid value and whose master is an object, with the step in docs/operations/seaweedfs-lowering-the-volume-size-limit.md. On the variants that run platform migrations, migration 57 does this. If the step is skipped, every such instance drops to 400 on the upgrade: each of its volumes at or above 400 MB leaves the master's writable set, and a bucket whose volumes have all crossed that line takes no writes until it can grow. Assisted-by: LLM Signed-off-by: Aleksei Sviridkin <f@lex.la>