From 45e7b53b013999e4cc2f72c080651cc2ece5a346 Mon Sep 17 00:00:00 2001
From: Ludovic Pouzenc <lpouzenc@gmail.com>
Date: Sun, 28 Jun 2015 01:05:47 +0200
Subject: RAID 5 layout implementation (left/right (as)symmetric and RAID 0
impl.
---
myraid.py | 122 +++++++++++++++++++++++++++++++++++++++++---------------------
1 file changed, 82 insertions(+), 40 deletions(-)
(limited to 'myraid.py')
diff --git a/myraid.py b/myraid.py
index 5b44fc4..3706c36 100644
--- a/myraid.py
+++ b/myraid.py
@@ -22,6 +22,8 @@ import logging, numpy
class MyRaid():
"""Auxiliary class, managing RAID layer"""
+ RAID_TYPES = [ '0', '1', '5', '5+0' ]
+ RAID5_LAYOUTS = [ 'la', 'ra', 'ls', 'rs' ]
def __init__(self, *args, **kwargs):
self.disks = []
@@ -31,7 +33,7 @@ class MyRaid():
self.raid_chunk_size = 65536
self.raid_disk_order = []
self.raid_disk_count = 0
- self.raid_types = [ '0', '1', '5', '5+0' ]
+ self.raid_layout = 'ls'
def get_raid_start(self):
return self.raid_start
@@ -48,6 +50,9 @@ class MyRaid():
def get_raid_disk_order_str(self):
return ' '.join(map(str,self.raid_disk_order))
+ def get_raid_layout(self):
+ return self.raid_layout
+
def set_disks(self, disks):
self.disks = disks
@@ -79,6 +84,12 @@ class MyRaid():
self.raid_disk_order = new_raid_disk_order
self.raid_disk_count = len(new_raid_disk_order)
+ def set_raid_layout(self, new_raid_layout):
+ if new_raid_layout in MyRaid.RAID5_LAYOUTS:
+ self.raid_layout = new_raid_layout
+ else:
+ raise ValueError('raid_layout has to be one of %s'%' '.join(RAID_LAYOUTS))
+
def sizeof_raid_result(self, raid_type):
size = self.raid_end - self.raid_start
if size <= 0 :
@@ -86,14 +97,11 @@ class MyRaid():
else:
return {
'0' : size * self.raid_disk_count,
- '1' : size,
+ '1' : size if self.raid_disk_count == 2 else 0,
'5' : size * (self.raid_disk_count - 1) if self.raid_disk_count >= 3 else 0,
'5+0': size * (self.raid_disk_count - 2) if self.raid_disk_count >= 6 and self.raid_disk_count % 2 == 0 else 0,
}[raid_type]
- def sizeof_disk_parity(self, raid_type):
- return self.sizeof_disk_xor(raid_type) / self.raid_sector_size * 16
-
def sizeof_disk_xor(self, raid_type):
size = self.raid_end - self.raid_start
if size <= 0:
@@ -101,16 +109,20 @@ class MyRaid():
else:
return {
'0' : 0, # TODO Could contain some plain text error message
- '1' : size,
+ '1' : size if self.raid_disk_count == 2 else 0,
'5' : size if self.raid_disk_count >= 3 else 0,
'5+0': size if self.raid_disk_count >= 6 and self.raid_disk_count % 2 == 0 else 0,
}[raid_type]
+ def sizeof_disk_parity(self, raid_type):
+ return self.sizeof_disk_xor(raid_type) / self.raid_sector_size * 16
+
def xor_blocks(self,fd_list, offset, size):
- """TODO"""
+ """Compute bitwise XOR against a bunch of disks slice"""
logging.info("Enter xor_blocks(fd_list,%d,%d)"%(offset, size))
- assert(size % 8 == 0), "Size must be multiple of 8"
+ if size % 8 != 0:
+ raise ValueError('xor_blocks : size must be multiple of 8')
dt = numpy.dtype('<Q8')
fd_list[0].seek(offset)
@@ -146,53 +158,83 @@ class MyRaid():
#logging.warn(binascii.hexlify(numpy_b1))
return (result,numpy_b1)
+ def read_disk_xor(self,raid_type,offset,size):
+ raid_disks = [ self.disks[i] for i in self.raid_disk_order ]
+ return self.xor_blocks(raid_disks,offset,size)[1].tostring()
+
def read_disk_parity(self,raid_type,offset,size):
- """TODO"""
- logging.warn("Enter check_data(%s,disks,%d,%d)"%(raid_type,offset,size))
+ """Returns textual information about parity status of each sector"""
+ logging.warn("Enter read_disk_parity(%s,%d,%d)"%(raid_type,offset,size))
raid_disks = [ self.disks[i] for i in self.raid_disk_order ]
start = self.raid_start + offset * self.raid_sector_size / 16
end = start + size * self.raid_sector_size / 16
- result = ''.join(
- [ '0x%011x %c\n'%( addr, self.xor_blocks(raid_disks, addr, self.raid_sector_size)[0])
- for addr in range(start, end, self.raid_sector_size)
- ])
-
- logging.warn("Exit. check_data(%s,disks,%d,%d)"%(raid_type,offset,size))
- return result
+ #TODO : improove for nested levels
+ if raid_type in ['1','5', '5+0']:
+ result = ''.join(
+ [ '0x%011x %c\n'%( addr, self.xor_blocks(raid_disks, addr, self.raid_sector_size)[0])
+ for addr in range(start, end, self.raid_sector_size)
+ ])
+ else:
+ result = None
- def read_disk_xor(self,raid_type,offset,size):
- raid_disks = [ self.disks[i] for i in self.raid_disk_order ]
- return self.xor_blocks(raid_disks,offset,size)[1].tostring()
+ logging.warn("Exit. read_disk_parity(%s,%d,%d)"%(raid_type,offset,size))
+ return result
def read_raid_result(self,raid_type,offset,size):
- """TODO"""
+ """Returns actual RAID data"""
+ raid_disks = [ self.disks[i] for i in self.raid_disk_order ] # TODO A garder en attribut ?
disk_count = len(self.raid_disk_order) # TODO doublon ?
- raid_disks = [ self.disks[i] for i in self.raid_disk_order ] # A garder en attribut ?
-
- # This code is RAID 5 only (left-assymetric)
- if disk_count < 3:
- return None
-
- slice_no = offset / self.raid_chunk_size
- slice_off = offset % self.raid_chunk_size
- segment=slice_no/(disk_count-1)
- par_disk=(disk_count-1) - (segment % disk_count) # TODO : equivalent a : segment-1 % disk_count ?
- data_disk=( par_disk + 1 + (slice_no % (disk_count-1)) ) % disk_count
- off_disk = self.raid_start + segment * self.raid_chunk_size + slice_off
-
- size2 = min(size, (slice_no+1) * self.raid_chunk_size - offset)
-
- logging.info("raid.read_result(%s): offset=%d,slice_no=%d,slice_off=%d,segment=%d,par_disk=%d,data_disk=%d,off_disk=%d,size2=%d,slice_off+size2=%d"
- % (raid_type,offset,slice_no,slice_off,segment,par_disk,data_disk,off_disk,size2,slice_off+size2) )
+ if raid_type == '0':
+ segment_no = offset / self.raid_chunk_size
+ segment_off = offset % self.raid_chunk_size
+ stripe_no = segment_no / disk_count
+ par_disk = -1
+ data_disk = segment_no % disk_count
+ off_disk = self.raid_start + stripe_no * self.raid_chunk_size + segment_off
+ size2 = min(size, (segment_no+1) * self.raid_chunk_size - offset)
+
+ elif raid_type == '1':
+ segment_no = -1
+ segment_off = -1
+ stripe_no = -1
+ par_disk = 1
+ data_disk = 0
+ off_disk = self.raid_start + offset
+ size2 = size
+
+ elif raid_type == '5':
+ segment_no = offset / self.raid_chunk_size
+ segment_off = offset % self.raid_chunk_size
+ stripe_no = segment_no / (disk_count-1)
+
+ if self.raid_layout in ['ls','la']:
+ par_disk = (disk_count-1) - (stripe_no % disk_count)
+ else: # self.raid_layout in ['rs','ra']:
+ par_disk = stripe_no % disk_count
+
+ if self.raid_layout in ['ls','rs']:
+ data_disk = (par_disk+1 + (segment_no % (disk_count-1)) ) % disk_count
+ else: # self.raid_layout in ['la','ra']:
+ data_disk = segment_no % (disk_count-1)
+ if data_disk >= par_disk:
+ data_disk = data_disk + 1
+
+ off_disk = self.raid_start + stripe_no * self.raid_chunk_size + segment_off
+ size2 = min(size, (segment_no+1) * self.raid_chunk_size - offset)
+
+ logging.info("raid.read_result(%s): offset=%d,segment_no=%d,segment_off=%d,stripe_no=%d,par_disk=%d,data_disk=%d,off_disk=%d,size2=%d,segment_off+size2=%d"
+ % (raid_type,offset,segment_no,segment_off,stripe_no,par_disk,data_disk,off_disk,size2,segment_off+size2) )
+
+ #TODO recorver from parity if damaged sectors in data_disk
data_fd = raid_disks[data_disk]
data_fd.seek(off_disk)
data = data_fd.read(size2)
-
+
# This kills performance but don't make short reads before EOF
- #if size2 < size:
+ #if size2 > 0 and size2 < size:
# data += self.read_result(self,raid_type,offset+size2,size-size2)
return data
--
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