[lustre-discuss] FLR mirroring on 2.12.1-1

[Jinshan Xiong]

hmm.. This definitely is not expected. As long as ost 1 is down, it should
be returned immediately from OSC layer and tries to read the 2nd mirror
that is located on ost 7. For the following blocks, it should not even try
ost1 but go to 7 directly.

Would you please collect Lustre log and send it to me? You can collect logs
on client side as follows:
0. create mirrored file
1. lctl set_param debug=-1 && lctl clear
2. lctl mark "======= start ========"
3. read the file
4. lctl dk > log.txt

and send me the log.txt file. If you can reproduce this problem
consistently, please use a small file so that it would be easier to check
the log.

Jinshan

On Mon, May 20, 2019 at 6:20 AM John Doe <ace629426 at gmail.com> wrote:

> It turns out that the read eventually finished and was 1/10th of the
> performance that I was expecting.
>
> As ost idx 1 is unavailable, the client read has to timeout on ost idx 1
> and then will read from ost idx 7. This happens for each 1MB block, as I am
> using that as the block size.
>
> Is there a tunable to avoid this issue?
>
> lfs check osts also takes about 30 seconds as it times out on the
> unavailable OST.
>
> Due to this issue, I am virtually unable to use the mirroring feature.
>
> I
>
> On Sun, May 19, 2019 at 4:27 PM John Doe <ace629426 at gmail.com> wrote:
>
>> After mirroring a file , when one mirror is down, any reads from a client
>> just hangs. Both server and client are running latest 2.12.1-1. Client
>> waits for ost idx 1 to come back online.  I am only unmounting ost idx1 not
>> ost idx 7.
>>
>> Has anyone tried this feature?
>>
>> Thanks,
>> John.
>>
>> lfs getstripe mirror10
>> mirror10
>>   lcm_layout_gen:    5
>>   lcm_mirror_count:  2
>>   lcm_entry_count:   2
>>     lcme_id:             65537
>>     lcme_mirror_id:      1
>>     lcme_flags:          init
>>     lcme_extent.e_start: 0
>>     lcme_extent.e_end:   EOF
>>       lmm_stripe_count:  1
>>       lmm_stripe_size:   1048576
>>       lmm_pattern:       raid0
>>       lmm_layout_gen:    0
>>       lmm_stripe_offset: 1
>>       lmm_pool:          01
>>       lmm_objects:
>>       - 0: { l_ost_idx: 1, l_fid: [0x100010000:0x280a8:0x0] }
>>
>>     lcme_id:             131074
>>     lcme_mirror_id:      2
>>     lcme_flags:          init
>>     lcme_extent.e_start: 0
>>     lcme_extent.e_end:   EOF
>>       lmm_stripe_count:  1
>>       lmm_stripe_size:   1048576
>>       lmm_pattern:       raid0
>>       lmm_layout_gen:    0
>>       lmm_stripe_offset: 7
>>       lmm_pool:          02
>>       lmm_objects:
>>       - 0: { l_ost_idx: 7, l_fid: [0x100070000:0x28066:0x0] }
>>
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