/// <summary>
/// "All disks holding extents for a given volume must have the same sector size"
/// </summary>
public static int?GetBytesPerSector(List <DynamicColumn> columns)
{
foreach (DynamicColumn column in columns)
{
int?bytesPerSector = DynamicColumn.GetBytesPerSector(column.Extents);
if (bytesPerSector.HasValue)
{
return(bytesPerSector.Value);
}
}
return(null);
}
public override void WriteSectors(long sectorIndex, byte[] data)
{
int sectorCount = data.Length / this.BytesPerSector;
List <ArrayPosition> writePositions = TranslateSectors(sectorIndex, sectorCount);
int bytesWritten = 0;
foreach (ArrayPosition writePosition in writePositions)
{
byte[] stripeBytes = new byte[writePosition.SectorCount * this.BytesPerSector];
Array.Copy(data, bytesWritten, stripeBytes, 0, stripeBytes.Length);
DynamicColumn column = m_columns[writePosition.DiskIndex];
column.WriteSectors(writePosition.SectorIndex, stripeBytes);
bytesWritten += stripeBytes.Length;
}
}
public override byte[] ReadSectors(long sectorIndex, int sectorCount)
{
List <ArrayPosition> readPositions = TranslateSectors(sectorIndex, sectorCount);
byte[] result = new byte[sectorCount * BytesPerSector];
int bytesRead = 0;
foreach (ArrayPosition readPosition in readPositions)
{
DynamicColumn column = m_columns[readPosition.DiskIndex];
byte[] stripeBytes = column.ReadSectors(readPosition.SectorIndex, (int)readPosition.SectorCount);
Array.Copy(stripeBytes, 0, result, bytesRead, stripeBytes.Length);
bytesRead += stripeBytes.Length;
}
return(result);
}
public override byte[] ReadSectors(long sectorIndex, int sectorCount)
{
CheckBoundaries(sectorIndex, sectorCount);
List <ArrayPosition> readPositions = TranslateSectors(sectorIndex, sectorCount);
byte[] result = new byte[sectorCount * BytesPerSector];
int bytesRead = 0;
foreach (ArrayPosition readPosition in readPositions)
{
DynamicColumn column = m_columns[readPosition.DiskIndex];
byte[] stripeBytes;
if (column.IsOperational)
{
stripeBytes = column.ReadSectors(readPosition.SectorIndex, readPosition.SectorCount);
}
else
{
stripeBytes = new byte[readPosition.SectorCount * BytesPerDynamicDiskSector];
for (int index = 0; index < m_columns.Count; index++)
{
if (index != readPosition.DiskIndex)
{
byte[] currentBytes = m_columns[index].ReadSectors(readPosition.SectorIndex, readPosition.SectorCount);
stripeBytes = XOR(stripeBytes, currentBytes);
}
}
}
Array.Copy(stripeBytes, 0, result, bytesRead, stripeBytes.Length);
bytesRead += stripeBytes.Length;
}
return(result);
}
// We support degraded arrays
public override void WriteSectors(long sectorIndex, byte[] data)
{
CheckBoundaries(sectorIndex, data.Length / this.BytesPerSector);
int numberOfColumns = m_columns.Count;
int sectorCount = data.Length / this.BytesPerSector;
List <ArrayPosition> writePositions = TranslateSectors(sectorIndex, sectorCount);
int bytesWritten = 0;
foreach (ArrayPosition writePosition in writePositions)
{
DynamicColumn column = m_columns[writePosition.DiskIndex];
byte[] stripeBytes = new byte[writePosition.SectorCount * this.BytesPerSector];
Array.Copy(data, bytesWritten, stripeBytes, 0, stripeBytes.Length);
// first we obtain the necessary data from the other columns
long stripeIndexInColumn = writePosition.SectorIndex / m_sectorsPerStripe;
int parityColumnIndex = (numberOfColumns - 1) - (int)(stripeIndexInColumn % numberOfColumns);
List <byte[]> segment = new List <byte[]>();
for (int index = 0; index < numberOfColumns; index++)
{
if (m_columns[index].IsOperational)
{
byte[] bytes = m_columns[index].ReadSectors(writePosition.SectorIndex, writePosition.SectorCount);
segment.Add(bytes);
}
else
{
segment.Add(null);
}
}
int missingColumnIndex = segment.IndexOf(null);
if (missingColumnIndex >= 0)
{
if (missingColumnIndex != parityColumnIndex && missingColumnIndex != writePosition.DiskIndex)
{
// let's calculate the missing data stripe
byte[] missingBytes = segment[parityColumnIndex];
for (int index = 0; index < numberOfColumns; index++)
{
if (index != missingColumnIndex && index != parityColumnIndex)
{
missingBytes = XOR(missingBytes, segment[index]);
}
}
segment[missingColumnIndex] = missingBytes;
}
}
if (column.IsOperational)
{
column.WriteSectors(writePosition.SectorIndex, stripeBytes);
}
if (missingColumnIndex != parityColumnIndex)
{
// lets calculate the new parity disk
segment[writePosition.DiskIndex] = stripeBytes;
byte[] parityBytes = new byte[writePosition.SectorCount * this.BytesPerSector];
for (int index = 0; index < numberOfColumns; index++)
{
if (index != parityColumnIndex)
{
parityBytes = XOR(parityBytes, segment[index]);
}
}
m_columns[parityColumnIndex].WriteSectors(writePosition.SectorIndex, parityBytes);
}
bytesWritten += stripeBytes.Length;
}
}
public SpannedVolume(DynamicColumn column, Guid volumeGuid, Guid diskGroupGuid) : base(volumeGuid, diskGroupGuid)
{
m_column = column;
}
