(unknown)

[Nitin Kshirsagar <nshirsagar-FZ1t8LVTR2ZWk0Htik3J/w@public.gmane.org>]

Hello Kent,

I have setup bcache and run fio data verification test on write back and write through caches.
The fio tests are passed, however I have found following issues while using bcache.

Issue1: Cache is not created as per user specified options  
--------------------------------------------------------------------------------------------------------
Steps:
1.Create cache by specifying mode writeback and cache replacement policy as fifo
[root@annu bcache]# make-bcache --cache  /dev/sdc --bdev /dev/sdd  --writeback --cache_replacement_policy=fifo 
UUID:                   e25f2840-f02b-46af-81e7-28948b2737cc
Set UUID:               68da5b89-1e87-457a-80c7-2c822737f969
nbuckets:               2048
block_size:             1
bucket_size:            1024
nr_in_set:              1
nr_this_dev:            0
first_bucket:           1
UUID:                   a3ce52e6-631b-4c74-afa2-9f8b0088c7f4
Set UUID:               68da5b89-1e87-457a-80c7-2c822737f969
nbuckets:               20480
block_size:             1
bucket_size:            1024
nr_in_set:              1
nr_this_dev:            0
first_bucket:           1

[root@annu bcache]# echo /dev/sdc > /sys/fs/bcache/register
[root@annu bcache]# echo /dev/sdd > /sys/fs/bcache/register


2. Cache mode should  be "writeback" instead of "writethrough"
[root@annu bcache]# cat /sys/block/bcache2/bcache/cache_mode
[writethrough] writeback writearound none
[root@annu bcache]# cat /sys/block/bcache2/bcache/writeback_running
1

3. Cache policy should be "fifo" instead of "lru" 
[root@annu ~]# cat /sys/block/bcache2/bcache/cache/cache0/cache_replacement_policy
[lru] fifo random


Issue2: Cache dirty data value should not be negative.
-------------------------------------------------------------------------------------------------------
Steps:

1.Create cache by specifying mode writeback and cache replacement policy as fifo
2.To make bcache devices known to the kernel
    [root@annu bcache]# echo /dev/sdc > /sys/fs/bcache/register
    [root@annu bcache]# echo /dev/sdd > /sys/fs/bcache/register
3.Create FS on cache  /dev/bcacheN and mount in directory
4.Create Data set by using fio or dd on mount point.
5. Change cache node from "writethrough" to "writeback"    
    [root@annu ~]# echo writeback >  /sys/block/bcache2/bcache/cache_mode
    [root@annu ~]# cat /sys/block/bcache2/bcache/cache_mode
    writethrough [writeback] writearound none
6.Check cache dirty data should not be negative value 
   [root@annu ~]# cat /sys/block/bcache2/bcache/dirty_data
   -9.4M


-- 
Thanks & Regards

Nitin Kshirsagar
Software Engr, QA
Cell 997.566.3985

STEC india private Limited, Pune | The SSD Company TM
NASDAQ STEC • Web www.stec-inc.com

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