do not have to use the same distributionAlgo as first pool (#19031)

when we expand via pools, there is no reason to stick
with the same distributionAlgo as the rest. Since the
algo only makes sense with-in a pool not across pools.

This allows for newer pools to use newer codepaths to
avoid legacy file lookups when they have a pre-existing
deployment from 2019, they can expand their new pool
to be of a newer distribution format, allowing the
pool to be more performant.

cmd/erasure-server-pool.go

@@ -72,15 +72,15 @@ func (z *erasureServerPools) SinglePool() bool {
 func newErasureServerPools(ctx context.Context, endpointServerPools EndpointServerPools) (ObjectLayer, error) {
 	var (
 		deploymentID       string
-		distributionAlgo   string
 		commonParityDrives int
 		err                error
 
 		formats      = make([]*formatErasureV3, len(endpointServerPools))
 		storageDisks = make([][]StorageAPI, len(endpointServerPools))
 		z            = &erasureServerPools{
-			serverPools: make([]*erasureSets, len(endpointServerPools)),
-			s3Peer:      NewS3PeerSys(endpointServerPools),
+			serverPools:      make([]*erasureSets, len(endpointServerPools)),
+			s3Peer:           NewS3PeerSys(endpointServerPools),
+			distributionAlgo: formatErasureVersionV3DistributionAlgoV3,
 		}
 	)
 
@@ -126,7 +126,7 @@ func newErasureServerPools(ctx context.Context, endpointServerPools EndpointServ
 
 		bootstrapTrace("waitForFormatErasure: loading disks", func() {
 			storageDisks[i], formats[i], err = waitForFormatErasure(local, ep.Endpoints, i+1,
-				ep.SetCount, ep.DrivesPerSet, deploymentID, distributionAlgo)
+				ep.SetCount, ep.DrivesPerSet, deploymentID)
 		})
 		if err != nil {
 			return nil, err
@@ -137,10 +137,6 @@ func newErasureServerPools(ctx context.Context, endpointServerPools EndpointServ
 			deploymentID = formats[i].ID
 		}
 
-		if distributionAlgo == "" {
-			distributionAlgo = formats[i].Erasure.DistributionAlgo
-		}
-
 		// Validate if users brought different DeploymentID pools.
 		if deploymentID != formats[i].ID {
 			return nil, fmt.Errorf("all pools must have same deployment ID - expected %s, got %s for pool(%s)", deploymentID, formats[i].ID, humanize.Ordinal(i+1))
@@ -157,10 +153,6 @@ func newErasureServerPools(ctx context.Context, endpointServerPools EndpointServ
 			z.deploymentID = uuid.MustParse(deploymentID)
 		}
 
-		if distributionAlgo != "" && z.distributionAlgo == "" {
-			z.distributionAlgo = distributionAlgo
-		}
-
 		for _, storageDisk := range storageDisks[i] {
 			if storageDisk != nil && storageDisk.IsLocal() {
 				localDrives = append(localDrives, storageDisk)