mdadm constant disk i/o

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mdadm constant disk i/o – Managing your servers can streamline the performance of your team by allowing them to complete complex tasks faster. Plus, it can enable them to detect problems early on before they get out of hand and compromise your business. As a result, the risk of experiencing operational setbacks is drastically lower.

But the only way to make the most of your server management is to perform it correctly. And to help you do so, this article will share nine tips on improving your server management and fix some problem about linux, hard-drive, mdadm, , .

I have an mdadm array which has constant disk i/o. I know it’s the array bc my server shows which specific drives have activity. According to iotop there’s a constant disk write of 3-6 Mbps, however, there are no corresponding processes in the list.

What could be causing this? It’s already been built, so it’s not from calculating parity or anything.

Solution :

It’s likely your RAID set is being checked. Some distros initiate an automatic background check of the RAID set from cron. On Debian-based systems, check out /etc/cron.daily/mdadm and /etc/cron.d/mdadm; there might be similar files on other distros.

You can see if a background check is running by looking in /sys/block/mdX/md/sync_action, as follows:

[root@localhost ~]# grep . /sys/block/*/md/sync_action
/sys/block/md0/md/sync_action:idle
/sys/block/md1/md/sync_action:idle

Have you created an ext3 or ext4 filesystem on this raid array ?

That disk activity was probably related to LazyInit :

mkfs.ext3 man page lazy init section :

lazy_itable_init[= <0 to disable, 1 to enable>]

If enabled and the uninit_bg feature is enabled, the inode table will
not be fully initialized by mke2fs.
This speeds up filesystem initialization noticeably,
but it requires the kernel to finish initializing the filesystem
in the background when the filesystem is first mounted.
If the option value is omitted, it defaults to 1 to enable lazy inode table zeroing.

more informations :

https://forums.linuxmint.com/viewtopic.php?t=212707

and

https://www.thomas-krenn.com/en/wiki/Ext4_Filesystem#Lazy_Initialization

and

ubuntuforums.org/showthread.php?t=2306568&p=13409940#post13409940

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