diff --git a/ctl/server.go b/ctl/server.go
index 07fdf887a..c72f7d379 100644
--- a/ctl/server.go
+++ b/ctl/server.go
@@ -18,7 +18,6 @@ import (
 	"fmt"
 	"time"
 
-	"github.com/pilosa/pilosa/v2"
 	"github.com/pilosa/pilosa/v2/server"
 	"github.com/pilosa/pilosa/v2/storage"
 	"github.com/spf13/cobra"
@@ -106,7 +105,7 @@ func BuildServerFlags(cmd *cobra.Command, srv *server.Command) {
 	// Transactional storage engine
 	// Note: the default for --tx must be kept "" empty string. Otherwise we
 	// cannot detect and honor the PILOSA_TXSRC env var over-ride.
-	flags.StringVarP(&srv.Config.Txsrc, "txsrc", "", "", fmt.Sprintf("transaction/storage to use: one of roaring, rbf, bolt, or a blue-green setup: rbf_roaring, roaring_rbf, bolt_roaring, roaring_bolt, bolt_rbf, etc. The default is: %v. The env var PILOSA_TXSRC is over-ridden by --txsrc option on the command line.", pilosa.DefaultTxsrc))
+	flags.StringVarP(&srv.Config.Txsrc, "txsrc", "", "", fmt.Sprintf("transaction/storage to use: one of roaring, rbf, bolt, or a blue-green setup: rbf_roaring, roaring_rbf, bolt_roaring, roaring_bolt, bolt_rbf, etc. The default is: %v. The env var PILOSA_TXSRC is over-ridden by --txsrc option on the command line.", storage.DefaultBackend))
 
 	// Storage
 	// Note: the default for --storage.backend must be kept "" empty string.
diff --git a/executor_test.go b/executor_test.go
index 906d0d276..8c5323303 100644
--- a/executor_test.go
+++ b/executor_test.go
@@ -540,7 +540,7 @@ func TestExecutor_Execute_Count(t *testing.T) {
 
 func roaringOnlyTest(t *testing.T) {
 	src := os.Getenv("PILOSA_TXSRC")
-	if src == pilosa.RoaringTxn || (pilosa.DefaultTxsrc == pilosa.RoaringTxn && src == "") {
+	if src == pilosa.RoaringTxn || (storage.DefaultBackend == pilosa.RoaringTxn && src == "") {
 		// okay to run, we are under roaring only
 	} else {
 		t.Skip("skip for everything but roaring")
diff --git a/fragment_internal_test.go b/fragment_internal_test.go
index fa45aace4..780a6d0b7 100644
--- a/fragment_internal_test.go
+++ b/fragment_internal_test.go
@@ -38,6 +38,7 @@ import (
 	"github.com/davecgh/go-spew/spew"
 	"github.com/pilosa/pilosa/v2/pql"
 	"github.com/pilosa/pilosa/v2/roaring"
+	"github.com/pilosa/pilosa/v2/storage"
 	"github.com/pilosa/pilosa/v2/testhook"
 	"github.com/pkg/errors"
 	"golang.org/x/sync/errgroup"
@@ -1720,7 +1721,7 @@ func TestFragment_RankCache_Persistence(t *testing.T) {
 
 func roaringOnlyTest(t *testing.T) {
 	src := os.Getenv("PILOSA_TXSRC")
-	if src == RoaringTxn || (DefaultTxsrc == RoaringTxn && src == "") {
+	if src == RoaringTxn || (storage.DefaultBackend == RoaringTxn && src == "") {
 		// okay to run, we are under roaring only
 	} else {
 		t.Skip("skip for everything but roaring")
@@ -1729,7 +1730,7 @@ func roaringOnlyTest(t *testing.T) {
 
 func roaringOnlyBenchmark(b *testing.B) {
 	src := os.Getenv("PILOSA_TXSRC")
-	if src == RoaringTxn || (DefaultTxsrc == RoaringTxn && src == "") {
+	if src == RoaringTxn || (storage.DefaultBackend == RoaringTxn && src == "") {
 		// okay to run, we are under roaring only
 	} else {
 		b.Skip("skip for everything but roaring")
diff --git a/pprof.go b/pprof.go
index 5c9b0b339..a13ef62d2 100644
--- a/pprof.go
+++ b/pprof.go
@@ -22,14 +22,18 @@ import (
 	"time"
 
 	_ "net/http/pprof" // Imported for its side-effect of registering pprof endpoints with the server.
+
+	"github.com/pilosa/pilosa/v2/storage"
 )
 
+// CPUProfileForDur (where "Dur" is short for "Duration"), is used for
+// performance tuning during development. It's only called—but is currently
+// commented out—in holder.go.
 func CPUProfileForDur(dur time.Duration, outpath string) {
-
 	// per-query pprof output:
 	txsrc := os.Getenv("PILOSA_TXSRC")
 	if txsrc == "" {
-		txsrc = DefaultTxsrc
+		txsrc = storage.DefaultBackend
 	}
 	path := outpath + "." + txsrc
 	f, err := os.Create(path)
@@ -48,12 +52,14 @@ func CPUProfileForDur(dur time.Duration, outpath string) {
 	}()
 }
 
+// MemProfileForDur (where "Dur" is short for "Duration"), is used for
+// performance tuning during development. It's only called—but is currently
+// commented out—in holder.go.
 func MemProfileForDur(dur time.Duration, outpath string) {
-
 	// per-query pprof output:
 	txsrc := os.Getenv("PILOSA_TXSRC")
 	if txsrc == "" {
-		txsrc = DefaultTxsrc
+		txsrc = storage.DefaultBackend
 	}
 	path := outpath + "." + txsrc
 	f, err := os.Create(path)
diff --git a/server/server.go b/server/server.go
index 0709aeddf..702f57b30 100644
--- a/server/server.go
+++ b/server/server.go
@@ -55,6 +55,7 @@ import (
 	"github.com/pilosa/pilosa/v2/statik"
 	"github.com/pilosa/pilosa/v2/stats"
 	"github.com/pilosa/pilosa/v2/statsd"
+	"github.com/pilosa/pilosa/v2/storage"
 	"github.com/pilosa/pilosa/v2/syswrap"
 	"github.com/pilosa/pilosa/v2/testhook"
 	"github.com/pkg/errors"
@@ -291,17 +292,17 @@ func (m *Command) SetupServer() error {
 	envTxsrc := os.Getenv("PILOSA_TXSRC")
 	if m.Config.Txsrc == "" {
 		// INVAR: No -tx flag on the command line.
-		// We defer to the environment, and then the DefaultTxsrc
+		// We defer to the environment, and then the DefaultBackend
 		if envTxsrc == "" {
 			// no env variable requested either.
-			m.Config.Txsrc = pilosa.DefaultTxsrc
+			m.Config.Txsrc = storage.DefaultBackend
 		} else {
 			// Tell the "regular" prod server what to use.
 			m.Config.Txsrc = envTxsrc
 		}
 	}
-	// INVAR: m.Config.Txsrc is valid and not "", but pilosa.DefaultTxsrc could be bad.
-	txty := pilosa.MustTxsrcToTxtype(m.Config.Txsrc) // will panic on unknown Txsrc.
+	// INVAR: m.Config.Storage.Backend is valid and not "", but storage.DefaultBackend could be bad.
+	txty := pilosa.MustTxsrcToTxtype(m.Config.Storage.Backend) // will panic on unknown Backend.
 	os.Setenv("PILOSA_TXSRC", m.Config.Txsrc)
 	m.logger.Printf("using Txsrc '%v'/%v", m.Config.Txsrc, txty)
 	if len(txty) == 2 {
diff --git a/stattx.go b/stattx.go
index 02b60d6e1..8004e795f 100644
--- a/stattx.go
+++ b/stattx.go
@@ -24,9 +24,9 @@ import (
 	"sync"
 	"time"
 
+	"github.com/pilosa/pilosa/v2/debugstats"
 	"github.com/pilosa/pilosa/v2/roaring"
 	txkey "github.com/pilosa/pilosa/v2/short_txkey"
-	//txkey "github.com/pilosa/pilosa/v2/txkey"
 )
 
 // statTx is useful to profile on a
@@ -69,29 +69,12 @@ func (w *callStats) reset() {
 	}
 }
 
-type LineSorter struct {
-	Line string
-	Tot  float64
-}
-
-type SortByTot []*LineSorter
-
-func (p SortByTot) Len() int {
-	return len(p)
-}
-func (p SortByTot) Less(i, j int) bool {
-	return p[i].Tot < p[j].Tot
-}
-func (p SortByTot) Swap(i, j int) {
-	p[i], p[j] = p[j], p[i]
-}
-
 func (c *callStats) report() (r string) {
 	txsrc := os.Getenv("PILOSA_TXSRC")
 	r = fmt.Sprintf("callStats: (%v)\n", txsrc)
 	c.mu.Lock()
 	defer c.mu.Unlock()
-	var lines []*LineSorter
+	var lines []*debugstats.LineSorter
 	for i := kall(0); i < kLast; i++ {
 		slc := c.elap[i].dur
 		n := len(slc)
@@ -105,9 +88,9 @@ func (c *callStats) report() (r string) {
 			totaltm = slc[0]
 		}
 		line := fmt.Sprintf("  %20v  N=%8v   avg/op: %12v   sd: %12v  total: %12v\n", i.String(), n, time.Duration(mean), time.Duration(sd), time.Duration(totaltm))
-		lines = append(lines, &LineSorter{Line: line, Tot: totaltm})
+		lines = append(lines, &debugstats.LineSorter{Line: line, Tot: totaltm})
 	}
-	sort.Sort(SortByTot(lines))
+	sort.Sort(debugstats.SortByTot(lines))
 	for i := range lines {
 		r += lines[i].Line
 	}
diff --git a/tx_test.go b/tx_test.go
index e9a74090c..b942651b2 100644
--- a/tx_test.go
+++ b/tx_test.go
@@ -24,6 +24,7 @@ import (
 	"github.com/pilosa/pilosa/v2"
 	"github.com/pilosa/pilosa/v2/http"
 	"github.com/pilosa/pilosa/v2/server"
+	"github.com/pilosa/pilosa/v2/storage"
 	"github.com/pilosa/pilosa/v2/test"
 )
 
@@ -61,9 +62,9 @@ func queryBalances(m0api *pilosa.API, acctOwnerID uint64, fldAcct0, fldAcct1, in
 
 func skipForRoaring(t *testing.T) {
 	src := os.Getenv("PILOSA_TXSRC")
-	// once txfactory.go DefaultTxsrc != RoaringTxn, this
+	// once txfactory.go storage.DefaultBackend != RoaringTxn, this
 	// will break, of course. Take out the src == "" below.
-	if (src == "" && pilosa.DefaultTxsrc == pilosa.RoaringTxn) || strings.Contains(src, "roaring") {
+	if (src == "" && storage.DefaultBackend == pilosa.RoaringTxn) || strings.Contains(src, "roaring") {
 		t.Skip("skip if roaring pseudo-txn involved -- won't show transactional rollback")
 	}
 }
diff --git a/txfactory.go b/txfactory.go
index 92018c03f..818bb8ac3 100644
--- a/txfactory.go
+++ b/txfactory.go
@@ -31,7 +31,6 @@ import (
 	"github.com/pilosa/pilosa/v2/roaring"
 	txkey "github.com/pilosa/pilosa/v2/short_txkey"
 	"github.com/pilosa/pilosa/v2/storage"
-	//txkey "github.com/pilosa/pilosa/v2/txkey"
 	"github.com/pkg/errors"
 	"github.com/zeebo/blake3"
 )
@@ -43,11 +42,6 @@ const (
 	BoltTxn    string = "bolt"
 )
 
-// DefaultTxsrc is set here. pilosa/server/config.go references it
-// to set the default for pilosa server exeutable.
-// Can be overridden with env variable PILOSA_TXSRC for testing.
-const DefaultTxsrc = RoaringTxn
-
 // DetectMemAccessPastTx true helps us catch places in api and executor
 // where mmapped memory is being accessed after the point in time
 // which the transaction has committed or rolled back. Since