serverPools := z.getServerPoolsAvailableSpace(ctx)
        total := serverPools.TotalAvailable()
        // choose when we reach this many
        choose := rand.Uint64() % total
        atTotal := uint64(0)
        for _, pool := range serverPools {
                atTotal += pool.Available
                if atTotal > choose && pool.Available > 0 {
                        return pool.Index

xlHeaderVersion version == 1:

```
//msgp:tuple xlMetaV2VersionHeader
type xlMetaV2VersionHeader struct {
 VersionID [16]byte  // Version UUID, raw.
 ModTime   int64     // Unix nanoseconds.
 Signature [4]byte   // Signature of metadata.
 Type      uint8     // Type if the version
 Flags     uint8
}
```

The following flags are defined:

```
const (