On 4/11/2019 11:23 PM, Yury Shevchuk wrote:
Hi Igor!
I have upgraded from Luminous to Nautilus and now slow device
expansion works indeed. The steps are shown below to round up the
topic.
node2# ceph osd df
ID CLASS WEIGHT REWEIGHT SIZE RAW USE DATA OMAP META AVAIL %USE VAR PGS STATUS
0 hdd 0.22739 1.00000 233 GiB 91 GiB 90 GiB 208 MiB 816 MiB 142 GiB 38.92 1.04 128 up
1 hdd 0.22739 1.00000 233 GiB 91 GiB 90 GiB 200 MiB 824 MiB 142 GiB 38.92 1.04 128 up
3 hdd 0.22739 0 0 B 0 B 0 B 0 B 0 B 0 B 0 0 0 down
2 hdd 0.22739 1.00000 481 GiB 172 GiB 90 GiB 201 MiB 823 MiB 309 GiB 35.70 0.96 128 up
TOTAL 947 GiB 353 GiB 269 GiB 610 MiB 2.4 GiB 594 GiB 37.28
MIN/MAX VAR: 0.96/1.04 STDDEV: 1.62
node2# lvextend -L+50G /dev/vg0/osd2
Size of logical volume vg0/osd2 changed from 400.00 GiB (102400 extents) to 450.00 GiB (115200 extents).
Logical volume vg0/osd2 successfully resized.
node2# ceph-bluestore-tool bluefs-bdev-expand --path /var/lib/ceph/osd/ceph-2/
inferring bluefs devices from bluestore path
2019-04-11 22:28:00.240 7f2e24e190c0 -1 bluestore(/var/lib/ceph/osd/ceph-2) _lock_fsid failed to lock /var/lib/ceph/osd/ceph-2/fsid (is another ceph-osd still running?)(11) Resource temporarily unavailable
...
*** Caught signal (Aborted) **
[two pages of stack dump stripped]
My mistake in the first place: I tried to expand non-stopped osd again.
node2# systemctl stop ceph-osd.target
node2# ceph-bluestore-tool bluefs-bdev-expand --path /var/lib/ceph/osd/ceph-2/
inferring bluefs devices from bluestore path
0 : device size 0x40000000 : own 0x[1000~3ffff000] = 0x3ffff000 : using 0x8ff000
1 : device size 0x1440000000 : own 0x[2000~143fffe000] = 0x143fffe000 : using 0x24dfe000
2 : device size 0x7080000000 : own 0x[3000000000~400000000] = 0x400000000 : using 0x0
Expanding...
2 : expanding from 0x6400000000 to 0x7080000000
2 : size label updated to 483183820800
node2# ceph-bluestore-tool show-label --dev /dev/vg0/osd2 | grep size
"size": 483183820800,
node2# ceph osd df
ID CLASS WEIGHT REWEIGHT SIZE RAW USE DATA OMAP META AVAIL %USE VAR PGS STATUS
0 hdd 0.22739 1.00000 233 GiB 91 GiB 90 GiB 208 MiB 816 MiB 142 GiB 38.92 1.10 128 up
1 hdd 0.22739 1.00000 233 GiB 91 GiB 90 GiB 200 MiB 824 MiB 142 GiB 38.92 1.10 128 up
3 hdd 0.22739 0 0 B 0 B 0 B 0 B 0 B 0 B 0 0 0 down
2 hdd 0.22739 1.00000 531 GiB 172 GiB 90 GiB 185 MiB 839 MiB 359 GiB 32.33 0.91 128 up
TOTAL 997 GiB 353 GiB 269 GiB 593 MiB 2.4 GiB 644 GiB 35.41
MIN/MAX VAR: 0.91/1.10 STDDEV: 3.37
It worked: AVAIL = 594+50 = 644. Great!
Thanks a lot for your help.
And one more question regarding your last remark is inline below.
On Wed, Apr 10, 2019 at 09:54:35PM +0300, Igor Fedotov wrote:
On 4/9/2019 1:59 PM, Yury Shevchuk wrote:
Igor, thank you, Round 2 is explained now.
Main aka block aka slow device cannot be expanded in Luminus, this
functionality will be available after upgrade to Nautilus.
Wal and db devices can be expanded in Luminous.
Now I have recreated osd2 once again to get rid of the paradoxical
cepf osd df output and tried to test db expansion, 40G -> 60G:
node2:/# ceph-volume lvm zap --destroy --osd-id 2
node2:/# ceph osd lost 2 --yes-i-really-mean-it
node2:/# ceph osd destroy 2 --yes-i-really-mean-it
node2:/# lvcreate -L1G -n osd2wal vg0
node2:/# lvcreate -L40G -n osd2db vg0
node2:/# lvcreate -L400G -n osd2 vg0
node2:/# ceph-volume lvm create --osd-id 2 --bluestore --data vg0/osd2 --block.db vg0/osd2db --block.wal vg0/osd2wal
node2:/# ceph osd df
ID CLASS WEIGHT REWEIGHT SIZE USE AVAIL %USE VAR PGS
0 hdd 0.22739 1.00000 233GiB 9.49GiB 223GiB 4.08 1.24 128
1 hdd 0.22739 1.00000 233GiB 9.49GiB 223GiB 4.08 1.24 128
3 hdd 0.22739 0 0B 0B 0B 0 0 0
2 hdd 0.22739 1.00000 400GiB 9.49GiB 391GiB 2.37 0.72 128
TOTAL 866GiB 28.5GiB 837GiB 3.29
MIN/MAX VAR: 0.72/1.24 STDDEV: 0.83
node2:/# lvextend -L+20G /dev/vg0/osd2db
Size of logical volume vg0/osd2db changed from 40.00 GiB (10240 extents) to 60.00 GiB (15360 extents).
Logical volume vg0/osd2db successfully resized.
node2:/# ceph-bluestore-tool bluefs-bdev-expand --path /var/lib/ceph/osd/ceph-2/
inferring bluefs devices from bluestore path
slot 0 /var/lib/ceph/osd/ceph-2//block.wal
slot 1 /var/lib/ceph/osd/ceph-2//block.db
slot 2 /var/lib/ceph/osd/ceph-2//block
0 : size 0x40000000 : own 0x[1000~3ffff000]
1 : size 0xf00000000 : own 0x[2000~9ffffe000]
2 : size 0x6400000000 : own 0x[3000000000~400000000]
Expanding...
1 : expanding from 0xa00000000 to 0xf00000000
1 : size label updated to 64424509440
node2:/# ceph-bluestore-tool show-label --dev /dev/vg0/osd2db | grep size
"size": 64424509440,
The label updated correctly, but ceph osd df have not changed.
I expected to see 391 + 20 = 411GiB in AVAIL column, but it stays at 391:
node2:/# ceph osd df
ID CLASS WEIGHT REWEIGHT SIZE USE AVAIL %USE VAR PGS
0 hdd 0.22739 1.00000 233GiB 9.50GiB 223GiB 4.08 1.24 128
1 hdd 0.22739 1.00000 233GiB 9.50GiB 223GiB 4.08 1.24 128
3 hdd 0.22739 0 0B 0B 0B 0 0 0
2 hdd 0.22739 1.00000 400GiB 9.49GiB 391GiB 2.37 0.72 128
TOTAL 866GiB 28.5GiB 837GiB 3.29
MIN/MAX VAR: 0.72/1.24 STDDEV: 0.83
I have restarted monitors on all three nodes, 391GiB stays intact.
OK, but I used bluefs-bdev-expand on running OSD... probably not good,
it seems to fork by opening bluefs directly... trying once again:
node2:/# systemctl stop ceph-osd@2
node2:/# lvextend -L+20G /dev/vg0/osd2db
Size of logical volume vg0/osd2db changed from 60.00 GiB (15360 extents) to 80.00 GiB (20480 extents).
Logical volume vg0/osd2db successfully resized.
node2:/# ceph-bluestore-tool bluefs-bdev-expand --path /var/lib/ceph/osd/ceph-2/
inferring bluefs devices from bluestore path
slot 0 /var/lib/ceph/osd/ceph-2//block.wal
slot 1 /var/lib/ceph/osd/ceph-2//block.db
slot 2 /var/lib/ceph/osd/ceph-2//block
0 : size 0x40000000 : own 0x[1000~3ffff000]
1 : size 0x1400000000 : own 0x[2000~9ffffe000]
2 : size 0x6400000000 : own 0x[3000000000~400000000]
Expanding...
1 : expanding from 0xa00000000 to 0x1400000000
1 : size label updated to 85899345920
node2:/# systemctl start ceph-osd@2
node2:/# systemctl restart ceph-mon@pier42
node2:/# ceph osd df
ID CLASS WEIGHT REWEIGHT SIZE USE AVAIL %USE VAR PGS
0 hdd 0.22739 1.00000 233GiB 9.49GiB 223GiB 4.08 1.24 128
1 hdd 0.22739 1.00000 233GiB 9.50GiB 223GiB 4.08 1.24 128
3 hdd 0.22739 0 0B 0B 0B 0 0 0
2 hdd 0.22739 1.00000 400GiB 9.50GiB 391GiB 2.37 0.72 0
TOTAL 866GiB 28.5GiB 837GiB 3.29
MIN/MAX VAR: 0.72/1.24 STDDEV: 0.83
Something is wrong. Maybe I was wrong expecting db change to appear
in AVAIL column? From Bluestore description I got db and slow should
sum up, no?
It was a while ago when db and slow were summed to provide total store size.
In the latest Luminous releases that's not true anymore. Ceph uses slow
device space to report SIZE/AVAIL only . There is some adjustment for BlueFS
part residing on the slow device but DB device is definitely out of
calculation here for now.
You can also note that reported SIZE for osd.2 is 400GiB in your case which
is absolutely inline with slow device capacity.
You are absolutely right, I could have noticed that myself...
Hence no DB involved.
I used this (admittedly not very recent) message as a guide for
volume sizing:
https://www.spinics.net/lists/ceph-devel/msg37804.html
It reads: "1GB for block.wal. For block.db, as much as you have."
I take it as follows:
1. block.db should be large enough to contain the active set, so the
slow aka block device is not touched often;
2. block.db + block should be large enough to contain all data
destined to this OSD by CRUSH.
That is, setups with block.db > block, or even block = 0 are possible
and useful. If that is correct, I cannot understand why only block
size is shown in ceph osd df AVAIL, while block.db is shown nowhere but
ceph-bluestore-tool show-label --dev /var/lib/ceph/osd/*/block.db.
But understanding "how it is" is precious too :)
Well - setups with low block size are theoretically possible but they
definitely aren't a mainstream and should be deployed with care and good
understanding how BlueStore/RocksDB work and what are your write
patterns. E.g. one has to realize when RocksDB performs a spillover to
slow device and how to avoid that (AFAIR there are some threads here
and/or at ceph-devel about that. This might be useful too:
https://tracker.ceph.com/issues/38745).
The case with block = 0 is actually the case where block is the only
device and hence there is no db. Which is absolutely valid once deployed
in "block-only" way.
Block only size is presented as OSD AVAIL due to the fact that DB and
block sizes aren't interchangeable, i.e. one is unable to put additional
user data when block free = 0 and db free != 0. So summing the size is
very confusing IMO.
Actually DB free/used size should be tracked separately. Nautilus has
some improvements on this way - it shows OMAP/META usage via 'ceph osd
df'. Probably DB total size should be presented too.
Thanks,
Igor
Regards,
-- Yury
PS I have written too much, out of letters :) Will follow up no more.
On Mon, Apr 08, 2019 at 10:17:24PM +0300, Igor Fedotov wrote:
Hi Yuri,
both issues from Round 2 relate to unsupported expansion for main device.
In fact it doesn't work and silently bypasses the operation in you case.
Please try with a different device...
Also I've just submitted a PR for mimic to indicate the bypass, will
backport to Luminous once mimic patch is approved.
See https://github.com/ceph/ceph/pull/27447
Thanks,
Igor
On 4/5/2019 4:07 PM, Yury Shevchuk wrote:
On Fri, Apr 05, 2019 at 02:42:53PM +0300, Igor Fedotov wrote:
wrt Round 1 - an ability to expand block(main) device has been added to
Nautilus,
see: https://github.com/ceph/ceph/pull/25308
Oh, that's good. But still separate wal&db may be good for studying
load on each volume (blktrace) or moving db/wal to another physical
disk by means of LVM transparently to ceph.
wrt Round 2:
- not setting 'size' label looks like a bug although I recall I fixed it...
Will double check.
- wrong stats output is probably related to the lack of monitor restart -
could you please try that and report back if it helps? Or even restart the
whole cluster.. (well I understand that's a bad approach for production but
just to verify my hypothesis)
Mon restart didn't help:
node0:~# systemctl restart ceph-mon@0
node1:~# systemctl restart ceph-mon@1
node2:~# systemctl restart ceph-mon@2
node2:~# ceph osd df
ID CLASS WEIGHT REWEIGHT SIZE USE AVAIL %USE VAR PGS
0 hdd 0.22739 1.00000 233GiB 9.44GiB 223GiB 4.06 0.12 128
1 hdd 0.22739 1.00000 233GiB 9.44GiB 223GiB 4.06 0.12 128
3 hdd 0.22739 0 0B 0B 0B 0 0 0
2 hdd 0.22739 1.00000 800GiB 409GiB 391GiB 51.18 1.51 128
TOTAL 1.24TiB 428GiB 837GiB 33.84
MIN/MAX VAR: 0.12/1.51 STDDEV: 26.30
Restarting mgrs and then all ceph daemons on all three nodes didn't
help either:
node2:~# ceph osd df
ID CLASS WEIGHT REWEIGHT SIZE USE AVAIL %USE VAR PGS
0 hdd 0.22739 1.00000 233GiB 9.43GiB 223GiB 4.05 0.12 128
1 hdd 0.22739 1.00000 233GiB 9.43GiB 223GiB 4.05 0.12 128
3 hdd 0.22739 0 0B 0B 0B 0 0 0
2 hdd 0.22739 1.00000 800GiB 409GiB 391GiB 51.18 1.51 128
TOTAL 1.24TiB 428GiB 837GiB 33.84
MIN/MAX VAR: 0.12/1.51 STDDEV: 26.30
Maybe we should upgrade to v14.2.0 Nautilus instead of studying old
bugs... after all, this is a toy cluster for now.
Thank you for responding,
-- Yury
On 4/5/2019 2:06 PM, Yury Shevchuk wrote:
Hello all!
We have a toy 3-node Ceph cluster running Luminous 12.2.11 with one
bluestore osd per node. We started with pretty small OSDs and would
like to be able to expand OSDs whenever needed. We had two issues
with the expansion: one turned out user-serviceable while the other
probably needs developers' look. I will describe both shortly.
Round 1
~~~~~~~
Trying to expand osd.2 by 1TB:
# lvextend -L+1T /dev/vg0/osd2
Size of logical volume vg0/osd2 changed from 232.88 GiB (59618 extents) to 1.23 TiB (321762 extents).
Logical volume vg0/osd2 successfully resized.
# ceph-bluestore-tool bluefs-bdev-expand --path /var/lib/ceph/osd/ceph-2
inferring bluefs devices from bluestore path
slot 1 /var/lib/ceph/osd/ceph-2//block
1 : size 0x13a38800000 : own 0x[1bf2200000~254300000]
Expanding...
1 : can't be expanded. Bypassing...
#
It didn't work. The explaination can be found in
ceph/src/os/bluestore/BlueFS.cc at line 310:
// returns true if specified device is under full bluefs control
// and hence can be expanded
bool BlueFS::is_device_expandable(unsigned id)
{
if (id >= MAX_BDEV || bdev[id] == nullptr) {
return false;
}
switch(id) {
case BDEV_WAL:
return true;
case BDEV_DB:
// true if DB volume is non-shared
return bdev[BDEV_SLOW] != nullptr;
}
return false;
}
So we have to use separate block.db and block.wal for OSD to be
expandable. Indeed, our OSDs were created without separate block.db
and block.wal, like this:
ceph-volume lvm create --bluestore --data /dev/vg0/osd2
Recreating osd.2 with separate block.db and block.wal:
# ceph-volume lvm zap --destroy --osd-id 2
# lvcreate -L1G -n osd2wal vg0
Logical volume "osd2wal" created.
# lvcreate -L40G -n osd2db vg0
Logical volume "osd2db" created.
# lvcreate -L400G -n osd2 vg0
Logical volume "osd2" created.
# ceph-volume lvm create --osd-id 2 --bluestore --data vg0/osd2 --block.db vg0/osd2db --block.wal vg0/osd2wal
Resync takes some time, and then we have expandable osd.2.
Round 2
~~~~~~~
Trying to expand osd.2 from 400G to 700G:
# lvextend -L+300G /dev/vg0/osd2
Size of logical volume vg0/osd2 changed from 400.00 GiB (102400 extents) to 700.00 GiB (179200 extents).
Logical volume vg0/osd2 successfully resized.
# ceph-bluestore-tool bluefs-bdev-expand --path /var/lib/ceph/osd/ceph-2/
inferring bluefs devices from bluestore path
slot 0 /var/lib/ceph/osd/ceph-2//block.wal
slot 1 /var/lib/ceph/osd/ceph-2//block.db
slot 2 /var/lib/ceph/osd/ceph-2//block
0 : size 0x40000000 : own 0x[1000~3ffff000]
1 : size 0xa00000000 : own 0x[2000~9ffffe000]
2 : size 0xaf00000000 : own 0x[3000000000~400000000]
Expanding...
#
This time expansion appears to work: 0xaf00000000 = 700GiB.
However, the size in the block device label have not changed:
# ceph-bluestore-tool show-label --dev /dev/vg0/osd2
{
"/dev/vg0/osd2": {
"osd_uuid": "a18ff7f7-0de1-4791-ba4b-f3b6d2221f44",
"size": 429496729600,
429496729600 = 400GiB
Worse, ceph osd df shows the added space as used, not available:
# ceph osd df
ID CLASS WEIGHT REWEIGHT SIZE USE AVAIL %USE VAR PGS
0 hdd 0.22739 1.00000 233GiB 8.06GiB 225GiB 3.46 0.13 128
1 hdd 0.22739 1.00000 233GiB 8.06GiB 225GiB 3.46 0.13 128
2 hdd 0.22739 1.00000 700GiB 301GiB 399GiB 43.02 1.58 64
TOTAL 1.14TiB 317GiB 849GiB 27.21
MIN/MAX VAR: 0.13/1.58 STDDEV: 21.43
If I expand osd.2 by another 100G, the space also goes to
"USE" column:
node2:~# ceph osd df
ID CLASS WEIGHT REWEIGHT SIZE USE AVAIL %USE VAR PGS
0 hdd 0.22739 1.00000 233GiB 8.05GiB 225GiB 3.46 0.10 128
1 hdd 0.22739 1.00000 233GiB 8.05GiB 225GiB 3.46 0.10 128
3 hdd 0.22739 0 0B 0B 0B 0 0 0
2 hdd 0.22739 1.00000 800GiB 408GiB 392GiB 51.01 1.52 128
TOTAL 1.24TiB 424GiB 842GiB 33.51
MIN/MAX VAR: 0.10/1.52 STDDEV: 26.54
So OSD expansion almost works, but not quite. If you had better luck
with bluefs-bdev-expand, could you please share your story?
-- Yury
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