On Jan 20, 2012, at 1:30 PM, Alexander Motin wrote:
> On 01/20/12 13:08, Nikolay Denev wrote:
>> On 20.01.2012, at 12:51, Alexander Motin<m...@freebsd.org> wrote:
>>
>>> On 01/20/12 10:09, Nikolay Denev wrote:
>>>> Another thing I've observed is that active/active probably only makes
>>>> sense if you are accessing single LUN.
>>>> In my tests where I have 24 LUNS that form 4 vdevs in a single zpool, the
>>>> highest performance was achieved
>>>> when I split the active paths among the controllers installed in the
>>>> server importing the pool. (basically "gmultipath rotate $LUN" in rc.local
>>>> for half of the paths)
>>>> Using active/active in this situation resulted in fluctuating performance.
>>>
>>> How big was fluctuation? Between speed of one and all paths?
>>>
>>> Several active/active devices without knowledge about each other with some
>>> probability will send part of requests via the same links, while ZFS itself
>>> already does some balancing between vdevs.
>>>
>>> --
>>> Alexander Motin
>>
>> I will test in a bit and post results.
>>
>> P.S.: Is there a way to enable/disable active-active on the fly? I'm
>> currently re-labeling to achieve that.
>
> No, there is not now. But for experiments you may achieve the same results by
> manually marking as failed all paths except one. It is not dangerous, as if
> that link fail, all other will resurrect automatically.
>
> --
> Alexander Motin
I had to destroy and relabel anyways, since I was not using active-active
currently. Here's what I did (maybe a little too verbose):
gmultipath label -A -v LD_0 /dev/da0 /dev/da24
gmultipath label -A -v LD_1 /dev/da1 /dev/da25
gmultipath label -A -v LD_2 /dev/da2 /dev/da26
gmultipath label -A -v LD_3 /dev/da3 /dev/da27
gmultipath label -A -v LD_4 /dev/da4 /dev/da28
gmultipath label -A -v LD_5 /dev/da5 /dev/da29
gmultipath label -A -v LD_6 /dev/da6 /dev/da30
gmultipath label -A -v LD_7 /dev/da7 /dev/da31
gmultipath label -A -v LD_8 /dev/da8 /dev/da32
gmultipath label -A -v LD_9 /dev/da9 /dev/da33
gmultipath label -A -v LD_10 /dev/da10 /dev/da34
gmultipath label -A -v LD_11 /dev/da11 /dev/da35
gmultipath label -A -v LD_12 /dev/da12 /dev/da36
gmultipath label -A -v LD_13 /dev/da13 /dev/da37
gmultipath label -A -v LD_14 /dev/da14 /dev/da38
gmultipath label -A -v LD_15 /dev/da15 /dev/da39
gmultipath label -A -v LD_16 /dev/da16 /dev/da40
gmultipath label -A -v LD_17 /dev/da17 /dev/da41
gmultipath label -A -v LD_18 /dev/da18 /dev/da42
gmultipath label -A -v LD_19 /dev/da19 /dev/da43
gmultipath label -A -v LD_20 /dev/da20 /dev/da44
gmultipath label -A -v LD_21 /dev/da21 /dev/da45
gmultipath label -A -v LD_22 /dev/da22 /dev/da46
gmultipath label -A -v LD_23 /dev/da23 /dev/da47
:~# gmultipath status
Name Status Components
multipath/LD_0 OPTIMAL da0 (ACTIVE)
da24 (ACTIVE)
multipath/LD_1 OPTIMAL da1 (ACTIVE)
da25 (ACTIVE)
multipath/LD_2 OPTIMAL da2 (ACTIVE)
da26 (ACTIVE)
multipath/LD_3 OPTIMAL da3 (ACTIVE)
da27 (ACTIVE)
multipath/LD_4 OPTIMAL da4 (ACTIVE)
da28 (ACTIVE)
multipath/LD_5 OPTIMAL da5 (ACTIVE)
da29 (ACTIVE)
multipath/LD_6 OPTIMAL da6 (ACTIVE)
da30 (ACTIVE)
multipath/LD_7 OPTIMAL da7 (ACTIVE)
da31 (ACTIVE)
multipath/LD_8 OPTIMAL da8 (ACTIVE)
da32 (ACTIVE)
multipath/LD_9 OPTIMAL da9 (ACTIVE)
da33 (ACTIVE)
multipath/LD_10 OPTIMAL da10 (ACTIVE)
da34 (ACTIVE)
multipath/LD_11 OPTIMAL da11 (ACTIVE)
da35 (ACTIVE)
multipath/LD_12 OPTIMAL da12 (ACTIVE)
da36 (ACTIVE)
multipath/LD_13 OPTIMAL da13 (ACTIVE)
da37 (ACTIVE)
multipath/LD_14 OPTIMAL da14 (ACTIVE)
da38 (ACTIVE)
multipath/LD_15 OPTIMAL da15 (ACTIVE)
da39 (ACTIVE)
multipath/LD_16 OPTIMAL da16 (ACTIVE)
da40 (ACTIVE)
multipath/LD_17 OPTIMAL da17 (ACTIVE)
da41 (ACTIVE)
multipath/LD_18 OPTIMAL da18 (ACTIVE)
da42 (ACTIVE)
multipath/LD_19 OPTIMAL da19 (ACTIVE)
da43 (ACTIVE)
multipath/LD_20 OPTIMAL da20 (ACTIVE)
da44 (ACTIVE)
multipath/LD_21 OPTIMAL da21 (ACTIVE)
da45 (ACTIVE)
multipath/LD_22 OPTIMAL da22 (ACTIVE)
da46 (ACTIVE)
multipath/LD_23 OPTIMAL da23 (ACTIVE)
da47 (ACTIVE)
:~# zpool import tank
:~# zpool status
pool: tank
state: ONLINE
scan: none requested
config:
NAME STATE READ WRITE CKSUM
tank ONLINE 0 0 0
raidz2-0 ONLINE 0 0 0
multipath/LD_0 ONLINE 0 0 0
multipath/LD_1 ONLINE 0 0 0
multipath/LD_2 ONLINE 0 0 0
multipath/LD_3 ONLINE 0 0 0
multipath/LD_4 ONLINE 0 0 0
multipath/LD_5 ONLINE 0 0 0
raidz2-1 ONLINE 0 0 0
multipath/LD_6 ONLINE 0 0 0
multipath/LD_7 ONLINE 0 0 0
multipath/LD_8 ONLINE 0 0 0
multipath/LD_9 ONLINE 0 0 0
multipath/LD_10 ONLINE 0 0 0
multipath/LD_11 ONLINE 0 0 0
raidz2-2 ONLINE 0 0 0
multipath/LD_12 ONLINE 0 0 0
multipath/LD_13 ONLINE 0 0 0
multipath/LD_14 ONLINE 0 0 0
multipath/LD_15 ONLINE 0 0 0
multipath/LD_16 ONLINE 0 0 0
multipath/LD_17 ONLINE 0 0 0
raidz2-3 ONLINE 0 0 0
multipath/LD_18 ONLINE 0 0 0
multipath/LD_19 ONLINE 0 0 0
multipath/LD_20 ONLINE 0 0 0
multipath/LD_21 ONLINE 0 0 0
multipath/LD_22 ONLINE 0 0 0
multipath/LD_23 ONLINE 0 0 0
errors: No known data errors
And now a very naive benchmark :
:~# dd if=/dev/zero of=/tank/TEST bs=1M count=512
512+0 records in
512+0 records out
536870912 bytes transferred in 7.282780 secs (73717855 bytes/sec)
:~# dd if=/dev/zero of=/tank/TEST bs=1M count=512
512+0 records in
512+0 records out
536870912 bytes transferred in 38.422724 secs (13972745 bytes/sec)
:~# dd if=/dev/zero of=/tank/TEST bs=1M count=512
512+0 records in
512+0 records out
536870912 bytes transferred in 10.810989 secs (49659740 bytes/sec)
Now deactivate the alternative paths :
/sbin/gmultipath fail LD_0 da24
/sbin/gmultipath fail LD_1 da25
/sbin/gmultipath fail LD_2 da26
/sbin/gmultipath fail LD_3 da27
/sbin/gmultipath fail LD_4 da28
/sbin/gmultipath fail LD_5 da29
/sbin/gmultipath fail LD_6 da6
/sbin/gmultipath fail LD_7 da7
/sbin/gmultipath fail LD_8 da8
/sbin/gmultipath fail LD_9 da9
/sbin/gmultipath fail LD_10 da10
/sbin/gmultipath fail LD_11 da11
/sbin/gmultipath fail LD_12 da36
/sbin/gmultipath fail LD_13 da37
/sbin/gmultipath fail LD_14 da38
/sbin/gmultipath fail LD_15 da39
/sbin/gmultipath fail LD_16 da40
/sbin/gmultipath fail LD_17 da41
/sbin/gmultipath fail LD_18 da18
/sbin/gmultipath fail LD_19 da19
/sbin/gmultipath fail LD_20 da20
/sbin/gmultipath fail LD_21 da21
/sbin/gmultipath fail LD_22 da22
/sbin/gmultipath fail LD_23 da23
:~# gmultipath status
Name Status Components
multipath/LD_0 DEGRADED da0 (ACTIVE)
da24 (FAIL)
multipath/LD_1 DEGRADED da1 (ACTIVE)
da25 (FAIL)
multipath/LD_2 DEGRADED da2 (ACTIVE)
da26 (FAIL)
multipath/LD_3 DEGRADED da3 (ACTIVE)
da27 (FAIL)
multipath/LD_4 DEGRADED da4 (ACTIVE)
da28 (FAIL)
multipath/LD_5 DEGRADED da5 (ACTIVE)
da29 (FAIL)
multipath/LD_6 DEGRADED da6 (FAIL)
da30 (ACTIVE)
multipath/LD_7 DEGRADED da7 (FAIL)
da31 (ACTIVE)
multipath/LD_8 DEGRADED da8 (FAIL)
da32 (ACTIVE)
multipath/LD_9 DEGRADED da9 (FAIL)
da33 (ACTIVE)
multipath/LD_10 DEGRADED da10 (FAIL)
da34 (ACTIVE)
multipath/LD_11 DEGRADED da11 (FAIL)
da35 (ACTIVE)
multipath/LD_12 DEGRADED da12 (ACTIVE)
da36 (FAIL)
multipath/LD_13 DEGRADED da13 (ACTIVE)
da37 (FAIL)
multipath/LD_14 DEGRADED da14 (ACTIVE)
da38 (FAIL)
multipath/LD_15 DEGRADED da15 (ACTIVE)
da39 (FAIL)
multipath/LD_16 DEGRADED da16 (ACTIVE)
da40 (FAIL)
multipath/LD_17 DEGRADED da17 (ACTIVE)
da41 (FAIL)
multipath/LD_18 DEGRADED da18 (FAIL)
da42 (ACTIVE)
multipath/LD_19 DEGRADED da19 (FAIL)
da43 (ACTIVE)
multipath/LD_20 DEGRADED da20 (FAIL)
da44 (ACTIVE)
multipath/LD_21 DEGRADED da21 (FAIL)
da45 (ACTIVE)
multipath/LD_22 DEGRADED da22 (FAIL)
da46 (ACTIVE)
multipath/LD_23 DEGRADED da23 (FAIL)
da47 (ACTIVE)
And the benchmark again:
:~# dd if=/dev/zero of=/tank/TEST bs=1M count=512
512+0 records in
512+0 records out
536870912 bytes transferred in 1.083226 secs (495622270 bytes/sec)
:~# dd if=/dev/zero of=/tank/TEST bs=1M count=512
512+0 records in
512+0 records out
536870912 bytes transferred in 1.409975 secs (380766249 bytes/sec)
:~# dd if=/dev/zero of=/tank/TEST bs=1M count=512
512+0 records in
512+0 records out
536870912 bytes transferred in 1.136110 secs (472551848 bytes/sec)
P.S.: The server is running 8.2-STABLE, dual port isp(4) card, and is directly
connected to a 4Gbps Xyratex dual-controller (active-active) storage array.
All the 24 SAS drives are setup as single disk RAID0
LUNs._______________________________________________
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