Re: [Scst-devel] Thin Provisioning and Ceph RBD's

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Hi Vlad,

On Mon, Jul 25, 2016 at 10:44 PM, Vladislav Bolkhovitin <vst@xxxxxxxx> wrote:
> Hi,
>
> I would suggest to rebuild SCST in the debug mode (after "make 2debug"), then before
> calling the unmap command enable "scsi" and "debug" logging for scst and scst_vdisk
> modules by 'echo add scsi >/sys/kernel/scst_tgt/trace_level; echo "add scsi"
>>/sys/kernel/scst_tgt/handlers/vdisk_fileio/trace_level; echo "add debug"
>>/sys/kernel/scst_tgt/handlers/vdisk_fileio/trace_level', then check, if for the unmap
> command vdisk_unmap_range() is reporting running blkdev_issue_discard() in the kernel
> logs.
>
> To double check, you might also add trace statement just before blkdev_issue_discard()
> in vdisk_unmap_range().

With the debug settings on, I am seeing the below output - this means
that discard is being sent to the backing (RBD) device, correct?

Including the ceph-users list to see if there is a reason RBD is not
processing this discard/unmap.

Thank you,
--
Alex Gorbachev
Storcium

Jul 26 08:23:38 e1 kernel: [  858.324715] [20426]: scst:
scst_cmd_done_local:2272:cmd ffff88201b552940, status 0, msg_status 0,
host_status 0, driver_status 0, resp_data_len 0
Jul 26 08:23:38 e1 kernel: [  858.324740] [20426]:
vdisk_parse_offset:2930:cmd ffff88201b552c00, lba_start 0, loff 0,
data_len 24
Jul 26 08:23:38 e1 kernel: [  858.324743] [20426]:
vdisk_unmap_range:3810:Unmapping lba 61779968 (blocks 8192)
Jul 26 08:23:38 e1 kernel: [  858.336218] [20426]: scst:
scst_cmd_done_local:2272:cmd ffff88201b552c00, status 0, msg_status 0,
host_status 0, driver_status 0, resp_data_len 0
Jul 26 08:23:38 e1 kernel: [  858.336232] [20426]:
vdisk_parse_offset:2930:cmd ffff88201b552ec0, lba_start 0, loff 0,
data_len 24
Jul 26 08:23:38 e1 kernel: [  858.336234] [20426]:
vdisk_unmap_range:3810:Unmapping lba 61788160 (blocks 8192)
Jul 26 08:23:38 e1 kernel: [  858.351446] [20426]: scst:
scst_cmd_done_local:2272:cmd ffff88201b552ec0, status 0, msg_status 0,
host_status 0, driver_status 0, resp_data_len 0
Jul 26 08:23:38 e1 kernel: [  858.351468] [20426]:
vdisk_parse_offset:2930:cmd ffff88201b553180, lba_start 0, loff 0,
data_len 24
Jul 26 08:23:38 e1 kernel: [  858.351471] [20426]:
vdisk_unmap_range:3810:Unmapping lba 61796352 (blocks 8192)
Jul 26 08:23:38 e1 kernel: [  858.373407] [20426]: scst:
scst_cmd_done_local:2272:cmd ffff88201b553180, status 0, msg_status 0,
host_status 0, driver_status 0, resp_data_len 0
Jul 26 08:23:38 e1 kernel: [  858.373422] [20426]:
vdisk_parse_offset:2930:cmd ffff88201b553440, lba_start 0, loff 0,
data_len 24
Jul 26 08:23:38 e1 kernel: [  858.373424] [20426]:
vdisk_unmap_range:3810:Unmapping lba 61804544 (blocks 8192)

Jul 26 08:24:04 e1 kernel: [  884.170201] [6290]: scst_cmd_init_done:829:CDB:
Jul 26 08:24:04 e1 kernel: [  884.170202]
(h)___0__1__2__3__4__5__6__7__8__9__A__B__C__D__E__F
Jul 26 08:24:04 e1 kernel: [  884.170205]    0: 42 00 00 00 00 00 00
00 18 00 00 00 00 00 00 00   B...............
Jul 26 08:24:04 e1 kernel: [  884.170268] [6290]: scst:
scst_parse_cmd:1312:op_name <UNMAP> (cmd ffff88201b556300),
direction=1 (expected 1, set yes), lba=0, bufflen=24, data len 24,
out_bufflen=0, (expected len data 24, expected len DIF 0, out expected
len 0), flags=0x80260, internal 0, naca 0
Jul 26 08:24:04 e1 kernel: [  884.173983] [20426]: scst:
scst_cmd_done_local:2272:cmd ffff88201b556b40, status 0, msg_status 0,
host_status 0, driver_status 0, resp_data_len 0
Jul 26 08:24:04 e1 kernel: [  884.173998] [20426]:
vdisk_parse_offset:2930:cmd ffff88201b556e00, lba_start 0, loff 0,
data_len 24
Jul 26 08:24:04 e1 kernel: [  884.174001] [20426]:
vdisk_unmap_range:3810:Unmapping lba 74231808 (blocks 8192)
Jul 26 08:24:04 e1 kernel: [  884.174224] [6290]: scst:
scst_cmd_init_done:828:NEW CDB: len 16, lun 16, initiator
iqn.1995-05.com.vihl2.ibft, target iqn.2008-10.net.storcium:scst.1,
queue_type 1, tag 4005936 (cmd ffff88201b5565c0, sess
ffff880ffa2c0000)
Jul 26 08:24:04 e1 kernel: [  884.174227] [6290]: scst_cmd_init_done:829:CDB:
Jul 26 08:24:04 e1 kernel: [  884.174228]
(h)___0__1__2__3__4__5__6__7__8__9__A__B__C__D__E__F
Jul 26 08:24:04 e1 kernel: [  884.174231]    0: 42 00 00 00 00 00 00
00 18 00 00 00 00 00 00 00   B...............
Jul 26 08:24:04 e1 kernel: [  884.174256] [6290]: scst:
scst_parse_cmd:1312:op_name <UNMAP> (cmd ffff88201b5565c0),
direction=1 (expected 1, set yes), lba=0, bufflen=24, data len 24,
out_bufflen=0, (expected len data 24, expected len DIF 0, out expected
len 0), flags=0x80260, internal 0, naca 0




>
> Alex Gorbachev wrote on 07/23/2016 08:48 PM:
>> Hi Nick, Vlad, SCST Team,
>>
>>>>> I have been looking at using the rbd-nbd tool, so that the caching is
>>>> provided by librbd and then use BLOCKIO with SCST. This will however need
>>>> some work on the SCST resource agents to ensure the librbd cache is
>>>> invalidated on ALUA state change.
>>>>>
>>>>> The other thing I have seen is this
>>>>>
>>>>> https://lwn.net/Articles/691871/
>>>>>
>>>>> Which may mean FILEIO will support thin provisioning sometime in the
>>>> future???
>>
>> I have run this configuration (RBD with BLOCKIO via SCST) through
>> VMWare's UNMAP test.  Basically, it runs:
>>
>> esxcli storage vmfs unmap -l <datastore>
>>
>> But the space is not reclaimed from RBD device, as is easily seen
>> polling the actual use (using method in
>> http://ceph.com/planet/real-size-of-a-ceph-rbd-image/)
>>
>> SCST thin_provisioned attribute in sysfs is showing 1
>>
>> Something appears to not be connecting the reclaim action.
>>
>> Thank you,
>> Alex
>
>
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