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XL: Implement strided erasure distribution. (#1772)

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Strided erasure distribution uses a new randomized
block distribution for each Put operation. This
information is captured inside `xl.json` for subsequent
Get operations.
This commit is contained in:
Harshavardhana
2016-05-26 19:55:48 -07:00
committed by Harshavardhana
parent 6dc8323684
commit d65101a8c8
7 changed files with 36 additions and 18 deletions
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14
xl-v1-metadata.go
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@@ -20,6 +20,7 @@ import (
"bytes"
"encoding/json"
"io"
"math/rand"
"path"
"sort"
"sync"
@@ -254,16 +255,15 @@ func (xl xlObjects) writeXLMetadata(bucket, prefix string, xlMeta xlMetaV1) erro
// randErasureDistribution - uses Knuth Fisher-Yates shuffle algorithm.
func randErasureDistribution(numBlocks int) []int {
rand.Seed(time.Now().UTC().UnixNano()) // Seed with current time.
distribution := make([]int, numBlocks)
for i := 0; i < numBlocks; i++ {
distribution[i] = i + 1
}
/*
for i := 0; i < numBlocks; i++ {
// Choose index uniformly in [i, numBlocks-1]
r := i + rand.Intn(numBlocks-i)
distribution[r], distribution[i] = distribution[i], distribution[r]
}
*/
for i := 0; i < numBlocks; i++ {
// Choose index uniformly in [i, numBlocks-1]
r := i + rand.Intn(numBlocks-i)
distribution[r], distribution[i] = distribution[i], distribution[r]
}
return distribution
}