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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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