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missing features ( raid subpart., format adv.opts ) and suggestion ( no raid reconstruction at install )

Recently I installed a ubuntu to drive a storage server (raid6) over 8 x 10TB disks plus 1 ssd cache disk and I found some features missing in order to be able in create subpartition of md0 and to pass some advanced options such as "-E lazy_itable_init=0,lazy_journal_init=0" to ext4 formatter.

Follow the procedure I used with missing feature highlighted:

- through manual partitioning

- created gpt bios boot (1M) and RAID physical foreach of raid drive members

- created raid level 6 using raid physical partitions

- missing : created two raid partitions md0p1 (5GB to hold /boot), md0p2 ; I needed to create a fake ext4 partition in order to allow partman to initialize partition with gpt by selecting md0 showing FREE SPACE from where I can now create my partitions. Elsewhere I can only create a single LVM on md0 but this can't work for the purpose of ssd caching because I need a un-cached partition ( md0p1 ) to load dm-cache modules at boot.

- created two physical LVM : vg0 (md0p1) and vg1 (md0p2)

- created two logical volumes : boot (vg0) and root (vg1)

- missing : unable to pass extended options such as lazy_itable_init=0 to ext4. This is important on a 50TB filesystem where background itable initialization can take days and itable_init=0 to mount option reduce that time but still hours instead of 15 mins because it flush only about 15mb/s while with extended lazy_itable_init=0 at filesystem allocation it works at max speed.

suggestion : raid reconstruction during install can slow down installation, would helpful when create raid to allow a checkbox ( disable reconstruction during install ) eg. echo 0 > /proc/sys/dev/raid/speed_limit_max . At reboot it will return to default 200000

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