There could be lots of difference between these 2 systems.
- What is the backend FS type? (ZFS or LDiskfs)
- How many MDT do you have?
- Is 2 threads enough to maximum your scan throughput? Stephane said he used 4
and 8 of them.
- What the workload running on the MDT at the same time, is it overloaded
already by your users' jobs?
Robinhood is also dumping its pipeline stats regularly in the logs. You can
spot which step of the pipeline is slowing you down.
Aurélien
Le 07/12/2020 20:59, « Kumar, Amit » <ahku...@mail.smu.edu> a écrit :
Hi Stephane & Aurélien
Here are the stats that I see in my logs:
Below is the best and worst avg. speed I noted in the log, with
nb_threads_scan=2:
2020/11/03 16:51:04 [4850/3] STATS | avg. speed (effective):
618.32 entries/sec (3.23 ms/entry/thread)
2020/11/25 18:06:10 [4850/3] STATS | avg. speed (effective):
187.93 entries/sec (10.62 ms/entry/thread)
Finally the full scan results are below:
2020/11/25 17:13:41 [4850/4] FS_Scan | Full scan of /scratch completed,
369729104 entries found (123 errors). Duration = 1964257.21s
Stephane, now I wonder what could have caused poor scanning performance.
Once I kicked off my initial scan during the LAD with same number of threads(2)
my scan along with some users jobs in the following days caused opening and
closing of file 150-200 million file operations and as a result filled up my
change log too soon than I expected. I had to cancel the first initial scan to
bring the situation under control. After I cleared change log, I asked
Robinhood to perform a new full scan. I am not sure if this cancel and restart
could have caused delays with additional lookup into database for existing
entries of already scanned 200millions files by then? Other thing your point
out is you have RAID10 SSD, on our end I have RAID-5 3.6TB of SSD's, this
probably explains the slowness?
I wasn't sure of the impact of the scan hence chose only 2 threads, I am
guessing I could bump that up to 4 next times to see if the benefits my scan
times.
Thank you,
Amit
-----Original Message-----
From: Stephane Thiell <sthi...@stanford.edu>
Sent: Monday, December 7, 2020 11:43 AM
To: Degremont, Aurelien <degre...@amazon.com>
Cc: Kumar, Amit <ahku...@mail.smu.edu>; Russell Dekema <deke...@umich.edu>;
lustre-discuss@lists.lustre.org
Subject: Re: [lustre-discuss] Robinhood scan time
Hi Amit,
Your number is very low indeed.
At our site, we're seeing ~100 million files/day during a Robinhood scan
with nb_threads_scan =4 and on hardware using Intel based CPUs:
2020/11/16 07:29:46 [126653/2] STATS | avg. speed (effective):
1207.06 entries/sec (3.31 ms/entry/thread)
2020/11/16 07:31:44 [126653/29] FS_Scan | Full scan of /oak completed,
1508197871 entries found (65 errors). Duration = 1249490.23s
In that case, our Lustre MDS and Robinhood server are running all on 2 x
CPU E5-2643 v3 @ 3.40GHz.
The Robinhood server has 768GB of RAM and 7TB of SSDs in RAID-10 for the DB.
On another filesystem, using AMD Naples -based CPUs and a dedicated
Robinhood DB, hosted a different server with AMD Rome CPUs, we’re seeing a rate
of 266M/day during a Robinhood scan with nb_threads_scan = 8:
2020/09/20 21:43:46 [25731/4] FS_Scan | Full scan of /fir completed,
877905438 entries found (744 errors). Duration = 284564.88s
Best,
Stephane
> On Dec 7, 2020, at 4:49 AM, Degremont, Aurelien <degre...@amazon.com>
wrote:
>
> Hi Amit,
>
> Thanks for this data point, that's interesting.
> Robinhood prints a scan summary in its logfile at the end of scan. It
could be nice if you can copy/paste it, for further reference.
>
> Aurélien
>
> Le 04/12/2020 23:39, « lustre-discuss au nom de Kumar, Amit »
<lustre-discuss-boun...@lists.lustre.org au nom de ahku...@mail.smu.edu> a
écrit :
>
> CAUTION: This email originated from outside of the organization. Do
not click links or open attachments unless you can confirm the sender and know
the content is safe.
>
>
>
> Dual Intel(R) Xeon(R) CPU E5-2680 v4 @ 2.40GHz;
> 256GB RAM
> System x3650 M5
> Storage for MDT is from NetApp EF560.
>
> Best regards,
> Amit
>
> -----Original Message-----
> From: Russell Dekema <deke...@umich.edu>
> Sent: Friday, December 4, 2020 4:27 PM
> To: Kumar, Amit <ahku...@mail.smu.edu>
> Cc: lustre-discuss@lists.lustre.org
> Subject: Re: [lustre-discuss] Robinhood scan time
>
> Greetings,
>
> What kind of hardware are you running on your metadata array?
>
> Cheers,
> Rusty Dekema
>
> On Fri, Dec 4, 2020 at 5:12 PM Kumar, Amit <ahku...@mail.smu.edu>
wrote:
>>
>> HI All,
>>
>>
>>
>> During LAD’20 Andreas mentioned if I could share the Robinhood scan time
for the 369millions files we have. So here it is. It took ~23 days for me to
complete initial scan of all 369 million files, on a dedicated robinhood server
that has 384GB RAM. I had it setup with all tweaks for database and client that
was mentioned in Robinhood document. I only used 2 threads for this scan. Hope
this reference helps.
>>
>>
>>
>> Thank you,
>>
>> Amit
>>
>>
>>
>> _______________________________________________
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>> lustre-discuss@lists.lustre.org
>> http://lists.lustre.org/listinfo.cgi/lustre-discuss-lustre.org
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>
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