[Gluster-users] performance.cache-size for high-RAM clients/servers, other tweaks for performance, and improvements to Gluster docs

Artem Russakovskii archon810 at gmail.com
Wed Apr 18 05:05:22 UTC 2018 

Hi Ravi,

Could you please expand on how these would help?

By forcing full here, we move the logic from the CPU to network, thus
decreasing CPU utilization, is that right? This is assuming the CPU and
disk utilization are caused by the differ and not by lstat and other calls
or something.

> Option: cluster.data-self-heal-algorithm
> Default Value: (null)
> Description: Select between "full", "diff". The "full" algorithm copies
> the entire file from source to sink. The "diff" algorithm copies to sink
> only those blocks whose checksums don't match with those of source. If no
> option is configured the option is chosen dynamically as follows: If the
> file does not exist on one of the sinks or empty file exists or if the
> source file size is about the same as page size the entire file will be
> read and written i.e "full" algo, otherwise "diff" algo is chosen.


I really have no idea what this means and how/why it would help. Any more
info on this option?

> Option: cluster.granular-entry-heal
> Default Value: no
> Description: If this option is enabled, self-heal will resort to granular
> way of recording changelogs and doing entry self-heal.


Thank you.


Sincerely,
Artem

--
Founder, Android Police <http://www.androidpolice.com>, APK Mirror
<http://www.apkmirror.com/>, Illogical Robot LLC
beerpla.net | +ArtemRussakovskii
<https://plus.google.com/+ArtemRussakovskii> | @ArtemR
<http://twitter.com/ArtemR>

On Tue, Apr 17, 2018 at 9:58 PM, Ravishankar N <ravishankar at redhat.com>
wrote:

>
> On 04/18/2018 10:14 AM, Artem Russakovskii wrote:
>
> Following up here on a related and very serious for us issue.
>
> I took down one of the 4 replicate gluster servers for maintenance today.
> There are 2 gluster volumes totaling about 600GB. Not that much data. After
> the server comes back online, it starts auto healing and pretty much all
> operations on gluster freeze for many minutes.
>
> For example, I was trying to run an ls -alrt in a folder with 7300 files,
> and it took a good 15-20 minutes before returning.
>
> During this time, I can see iostat show 100% utilization on the brick,
> heal status takes many minutes to return, glusterfsd uses up tons of CPU (I
> saw it spike to 600%). gluster already has massive performance issues for
> me, but healing after a 4-hour downtime is on another level of bad perf.
>
> For example, this command took many minutes to run:
>
> gluster volume heal androidpolice_data3 info summary
> Brick nexus2:/mnt/nexus2_block4/androidpolice_data3
> Status: Connected
> Total Number of entries: 91
> Number of entries in heal pending: 90
> Number of entries in split-brain: 0
> Number of entries possibly healing: 1
>
> Brick forge:/mnt/forge_block4/androidpolice_data3
> Status: Connected
> Total Number of entries: 87
> Number of entries in heal pending: 86
> Number of entries in split-brain: 0
> Number of entries possibly healing: 1
>
> Brick hive:/mnt/hive_block4/androidpolice_data3
> Status: Connected
> Total Number of entries: 87
> Number of entries in heal pending: 86
> Number of entries in split-brain: 0
> Number of entries possibly healing: 1
>
> Brick citadel:/mnt/citadel_block4/androidpolice_data3
> Status: Connected
> Total Number of entries: 0
> Number of entries in heal pending: 0
> Number of entries in split-brain: 0
> Number of entries possibly healing: 0
>
>
> Statistics showed a diminishing number of failed heals:
> ...
> Ending time of crawl: Tue Apr 17 21:13:08 2018
>
> Type of crawl: INDEX
> No. of entries healed: 2
> No. of entries in split-brain: 0
> No. of heal failed entries: 102
>
> Starting time of crawl: Tue Apr 17 21:13:09 2018
>
> Ending time of crawl: Tue Apr 17 21:14:30 2018
>
> Type of crawl: INDEX
> No. of entries healed: 4
> No. of entries in split-brain: 0
> No. of heal failed entries: 91
>
> Starting time of crawl: Tue Apr 17 21:14:31 2018
>
> Ending time of crawl: Tue Apr 17 21:15:34 2018
>
> Type of crawl: INDEX
> No. of entries healed: 0
> No. of entries in split-brain: 0
> No. of heal failed entries: 88
> ...
>
> Eventually, everything heals and goes back to at least where the roof
> isn't on fire anymore.
>
> The server stats and volume options were given in one of the previous
> replies to this thread.
>
> Any ideas or things I could run and show the output of to help diagnose?
> I'm also very open to working with someone on the team on a live debugging
> session if there's interest.
>
>
> It is likely that self-heal is causing the CPU spike due to the flood of
> lookups/ locks and checksum fops that the self-heal-daemon sends to the
> bricks.
> There's a script to control shd's cpu usage using cgroups. That should
> help in regulating self-heal traffic: https://review.gluster.org/#/
> c/18404/ (see extras/control-cpu-load.sh)
> Other self-heal related volume options that you could change are setting
> 'cluster.data-self-heal-algorithm' to 'full' and 'granular-entry-heal' to
> 'enable'.  `gluster volume set help` should give you more information about
> these options.
> Thanks,
> Ravi
>
>
>
> Thank you.
>
>
> Sincerely,
> Artem
>
> --
> Founder, Android Police <http://www.androidpolice.com>, APK Mirror
> <http://www.apkmirror.com/>, Illogical Robot LLC
> beerpla.net | +ArtemRussakovskii
> <https://plus.google.com/+ArtemRussakovskii> | @ArtemR
> <http://twitter.com/ArtemR>
>
> On Tue, Apr 10, 2018 at 9:56 AM, Artem Russakovskii <archon810 at gmail.com>
> wrote:
>
>> Hi Vlad,
>>
>> I actually saw that post already and even asked a question 4 days ago (
>> https://serverfault.com/questions/517775/glusterfs-direct-
>> i-o-mode#comment1172497_540917). The accepted answer also seems to go
>> against your suggestion to enable direct-io-mode as it says it should be
>> disabled for better performance when used just for file accesses.
>>
>> It'd be great if someone from the Gluster team chimed in about this
>> thread.
>>
>>
>> Sincerely,
>> Artem
>>
>> --
>> Founder, Android Police <http://www.androidpolice.com>, APK Mirror
>> <http://www.apkmirror.com/>, Illogical Robot LLC
>> beerpla.net | +ArtemRussakovskii
>> <https://plus.google.com/+ArtemRussakovskii> | @ArtemR
>> <http://twitter.com/ArtemR>
>>
>> On Tue, Apr 10, 2018 at 7:01 AM, Vlad Kopylov <vladkopy at gmail.com> wrote:
>>
>>> Wish I knew or was able to get detailed description of those options
>>> myself.
>>> here is direct-io-mode  https://serverfault.com/questi
>>> ons/517775/glusterfs-direct-i-o-mode
>>> Same as you I ran tests on a large volume of files, finding that main
>>> delays are in attribute calls, ending up with those mount options to add
>>> performance.
>>> I discovered those options through basically googling this user list
>>> with people sharing their tests.
>>> Not sure I would share your optimism, and rather then going up I
>>> downgraded to 3.12 and have no dir view issue now. Though I had to recreate
>>> the cluster and had to re-add bricks with existing data.
>>>
>>> On Tue, Apr 10, 2018 at 1:47 AM, Artem Russakovskii <archon810 at gmail.com
>>> > wrote:
>>>
>>>> Hi Vlad,
>>>>
>>>> I'm using only localhost: mounts.
>>>>
>>>> Can you please explain what effect each option has on performance
>>>> issues shown in my posts? "negative-timeout=10,attribute
>>>> -timeout=30,fopen-keep-cache,direct-io-mode=enable,fetch-attempts=5"
>>>> From what I remember, direct-io-mode=enable didn't make a difference in my
>>>> tests, but I suppose I can try again. The explanations about direct-io-mode
>>>> are quite confusing on the web in various guides, saying enabling it could
>>>> make performance worse in some situations and better in others due to OS
>>>> file cache.
>>>>
>>>> There are also these gluster volume settings, adding to the confusion:
>>>> Option: performance.strict-o-direct
>>>> Default Value: off
>>>> Description: This option when set to off, ignores the O_DIRECT flag.
>>>>
>>>> Option: performance.nfs.strict-o-direct
>>>> Default Value: off
>>>> Description: This option when set to off, ignores the O_DIRECT flag.
>>>>
>>>> Re: 4.0. I moved to 4.0 after finding out that it fixes the
>>>> disappearing dirs bug related to cluster.readdir-optimize if you remember (
>>>> http://lists.gluster.org/pipermail/gluster-users/2018-April/033830.html).
>>>> I was already on 3.13 by then, and 4.0 resolved the issue. It's been stable
>>>> for me so far, thankfully.
>>>>
>>>>
>>>> Sincerely,
>>>> Artem
>>>>
>>>> --
>>>> Founder, Android Police <http://www.androidpolice.com>, APK Mirror
>>>> <http://www.apkmirror.com/>, Illogical Robot LLC
>>>> beerpla.net | +ArtemRussakovskii
>>>> <https://plus.google.com/+ArtemRussakovskii> | @ArtemR
>>>> <http://twitter.com/ArtemR>
>>>>
>>>> On Mon, Apr 9, 2018 at 10:38 PM, Vlad Kopylov <vladkopy at gmail.com>
>>>> wrote:
>>>>
>>>>> you definitely need mount options to /etc/fstab
>>>>> use ones from here http://lists.gluster.org/piper
>>>>> mail/gluster-users/2018-April/033811.html
>>>>>
>>>>> I went on with using local mounts to achieve performance as well
>>>>>
>>>>> Also, 3.12 or 3.10 branches would be preferable for production
>>>>>
>>>>> On Fri, Apr 6, 2018 at 4:12 AM, Artem Russakovskii <
>>>>> archon810 at gmail.com> wrote:
>>>>>
>>>>>> Hi again,
>>>>>>
>>>>>> I'd like to expand on the performance issues and plead for help.
>>>>>> Here's one case which shows these odd hiccups: https://i.imgur.com/C
>>>>>> XBPjTK.gifv.
>>>>>>
>>>>>> In this GIF where I switch back and forth between copy operations on
>>>>>> 2 servers, I'm copying a 10GB dir full of .apk and image files.
>>>>>>
>>>>>> On server "hive" I'm copying straight from the main disk to an
>>>>>> attached volume block (xfs). As you can see, the transfers are relatively
>>>>>> speedy and don't hiccup.
>>>>>> On server "citadel" I'm copying the same set of data to a 4-replicate
>>>>>> gluster which uses block storage as a brick. As you can see, performance is
>>>>>> much worse, and there are frequent pauses for many seconds where nothing
>>>>>> seems to be happening - just freezes.
>>>>>>
>>>>>> All 4 servers have the same specs, and all of them have performance
>>>>>> issues with gluster and no such issues when raw xfs block storage is used.
>>>>>>
>>>>>> hive has long finished copying the data, while citadel is barely
>>>>>> chugging along and is expected to take probably half an hour to an hour. I
>>>>>> have over 1TB of data to migrate, at which point if we went live, I'm not
>>>>>> even sure gluster would be able to keep up instead of bringing the machines
>>>>>> and services down.
>>>>>>
>>>>>>
>>>>>>
>>>>>> Here's the cluster config, though it didn't seem to make any
>>>>>> difference performance-wise before I applied the customizations vs after.
>>>>>>
>>>>>> Volume Name: apkmirror_data1
>>>>>> Type: Replicate
>>>>>> Volume ID: 11ecee7e-d4f8-497a-9994-ceb144d6841e
>>>>>> Status: Started
>>>>>> Snapshot Count: 0
>>>>>> Number of Bricks: 1 x 4 = 4
>>>>>> Transport-type: tcp
>>>>>> Bricks:
>>>>>> Brick1: nexus2:/mnt/nexus2_block1/apkmirror_data1
>>>>>> Brick2: forge:/mnt/forge_block1/apkmirror_data1
>>>>>> Brick3: hive:/mnt/hive_block1/apkmirror_data1
>>>>>> Brick4: citadel:/mnt/citadel_block1/apkmirror_data1
>>>>>> Options Reconfigured:
>>>>>> cluster.quorum-count: 1
>>>>>> cluster.quorum-type: fixed
>>>>>> network.ping-timeout: 5
>>>>>> network.remote-dio: enable
>>>>>> performance.rda-cache-limit: 256MB
>>>>>> performance.readdir-ahead: on
>>>>>> performance.parallel-readdir: on
>>>>>> network.inode-lru-limit: 500000
>>>>>> performance.md-cache-timeout: 600
>>>>>> performance.cache-invalidation: on
>>>>>> performance.stat-prefetch: on
>>>>>> features.cache-invalidation-timeout: 600
>>>>>> features.cache-invalidation: on
>>>>>> cluster.readdir-optimize: on
>>>>>> performance.io-thread-count: 32
>>>>>> server.event-threads: 4
>>>>>> client.event-threads: 4
>>>>>> performance.read-ahead: off
>>>>>> cluster.lookup-optimize: on
>>>>>> performance.cache-size: 1GB
>>>>>> cluster.self-heal-daemon: enable
>>>>>> transport.address-family: inet
>>>>>> nfs.disable: on
>>>>>> performance.client-io-threads: on
>>>>>>
>>>>>>
>>>>>> The mounts are done as follows in /etc/fstab:
>>>>>> /dev/disk/by-id/scsi-0Linode_Volume_citadel_block1
>>>>>> /mnt/citadel_block1 xfs defaults 0 2
>>>>>> localhost:/apkmirror_data1 /mnt/apkmirror_data1 glusterfs
>>>>>> defaults,_netdev 0 0
>>>>>>
>>>>>> I'm really not sure if direct-io-mode mount tweaks would do anything
>>>>>> here, what the value should be set to, and what it is by default.
>>>>>>
>>>>>> The OS is OpenSUSE 42.3, 64-bit. 80GB of RAM, 20 CPUs, hosted by
>>>>>> Linode.
>>>>>>
>>>>>> I'd really appreciate any help in the matter.
>>>>>>
>>>>>> Thank you.
>>>>>>
>>>>>>
>>>>>> Sincerely,
>>>>>> Artem
>>>>>>
>>>>>> --
>>>>>> Founder, Android Police <http://www.androidpolice.com>, APK Mirror
>>>>>> <http://www.apkmirror.com/>, Illogical Robot LLC
>>>>>> beerpla.net | +ArtemRussakovskii
>>>>>> <https://plus.google.com/+ArtemRussakovskii> | @ArtemR
>>>>>> <http://twitter.com/ArtemR>
>>>>>>
>>>>>> On Thu, Apr 5, 2018 at 11:13 PM, Artem Russakovskii <
>>>>>> archon810 at gmail.com> wrote:
>>>>>>
>>>>>>> Hi,
>>>>>>>
>>>>>>> I'm trying to squeeze performance out of gluster on 4 80GB RAM
>>>>>>> 20-CPU machines where Gluster runs on attached block storage (Linode) in (4
>>>>>>> replicate bricks), and so far everything I tried results in sub-optimal
>>>>>>> performance.
>>>>>>>
>>>>>>> There are many files - mostly images, several million - and many
>>>>>>> operations take minutes, copying multiple files (even if they're small)
>>>>>>> suddenly freezes up for seconds at a time, then continues, iostat
>>>>>>> frequently shows large r_await and w_awaits with 100% utilization for the
>>>>>>> attached block device, etc.
>>>>>>>
>>>>>>> But anyway, there are many guides out there for small-file
>>>>>>> performance improvements, but more explanation is needed, and I think more
>>>>>>> tweaks should be possible.
>>>>>>>
>>>>>>> My question today is about performance.cache-size. Is this a size of
>>>>>>> cache in RAM? If so, how do I view the current cache size to see if it gets
>>>>>>> full and I should increase its size? Is it advisable to bump it up if I
>>>>>>> have many tens of gigs of RAM free?
>>>>>>>
>>>>>>>
>>>>>>>
>>>>>>> More generally, in the last 2 months since I first started working
>>>>>>> with gluster and set a production system live, I've been feeling frustrated
>>>>>>> because Gluster has a lot of poorly-documented and confusing options. I
>>>>>>> really wish documentation could be improved with examples and better
>>>>>>> explanations.
>>>>>>>
>>>>>>> Specifically, it'd be absolutely amazing if the docs offered a
>>>>>>> strategy for setting each value and ways of determining more optimal
>>>>>>> values. For example, for performance.cache-size, if it said something like
>>>>>>> "run command abc to see your current cache size, and if it's hurting, up
>>>>>>> it, but be aware that it's limited by RAM," it'd be already a huge
>>>>>>> improvement to the docs. And so on with other options.
>>>>>>>
>>>>>>>
>>>>>>>
>>>>>>> The gluster team is quite helpful on this mailing list, but in a
>>>>>>> reactive rather than proactive way. Perhaps it's tunnel vision once you've
>>>>>>> worked on a project for so long where less technical explanations and even
>>>>>>> proper documentation of options takes a back seat, but I encourage you to
>>>>>>> be more proactive about helping us understand and optimize Gluster.
>>>>>>>
>>>>>>> Thank you.
>>>>>>>
>>>>>>> Sincerely,
>>>>>>> Artem
>>>>>>>
>>>>>>> --
>>>>>>> Founder, Android Police <http://www.androidpolice.com>, APK Mirror
>>>>>>> <http://www.apkmirror.com/>, Illogical Robot LLC
>>>>>>> beerpla.net | +ArtemRussakovskii
>>>>>>> <https://plus.google.com/+ArtemRussakovskii> | @ArtemR
>>>>>>> <http://twitter.com/ArtemR>
>>>>>>>
>>>>>>
>>>>>>
>>>>>> _______________________________________________
>>>>>> Gluster-users mailing list
>>>>>> Gluster-users at gluster.org
>>>>>> http://lists.gluster.org/mailman/listinfo/gluster-users
>>>>>>
>>>>>
>>>>>
>>>>
>>>
>>
>
>
> _______________________________________________
> Gluster-users mailing listGluster-users at gluster.orghttp://lists.gluster.org/mailman/listinfo/gluster-users
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