Lo! You afaics want to configure the hdd as "writemostly". Google for the term in combination with "linux" or "mdadm". It'll lead to pages like this: http://tansi.info/hybrid/ http://hatim.eu/2014/05/25/leveraging-ssd-ephemeral-disks-in-ec2-part-2/ HTH, CU, knurd P.S.: I considered not answering the question, because it afaics and imho is off topic here (hence a answer only encourages people to send more questions like this), as the question is not specific to Fedora in any way. But this list is for "*Fedora kernel development*. This list is used for discussion of changes to the Fedora kernel that aren't necessarily relevant to the upstream kernel list. […]" (quote from https://lists.fedoraproject.org/admin/lists/kernel.lists.fedoraproject.org/ ) Hence I think you should send questions like that to a more general Linux kernel mailing list in the future. But as I said: That just my option. On 11.02.2017 15:16, Reindl Harald wrote: > /dev/sda: Samsung SSD 850 EVO 2TB > /dev/sdb: Samsung SSD 850 EVO 2TB > /dev/sdc: ST2000DX002-2DV164 > /dev/sdd: ST2000DX002-2DV164 > > normally i would expect that for heavy read-IO the two HDD drives would > sleep and the two SSD working more or less like a RAID0 but as example > running a btrfs-srub within a virtual machine on a 1.5 TB vdisk you can > hear the rotating disks clearly and there are also unexpected lags while > a disk IO auf around 700 MB/sec shows that it's basicly working > > pretty sure the lags are coming because read-access is also spread to > HDD - why is that? > > /dev/md2: > Version : 1.1 > Creation Time : Wed Jun 8 13:10:56 2011 > Raid Level : raid10 > Array Size : 3875222528 (3695.70 GiB 3968.23 GB) > Used Dev Size : 1937611264 (1847.85 GiB 1984.11 GB) > Raid Devices : 4 > Total Devices : 4 > Persistence : Superblock is persistent > > Intent Bitmap : Internal > > Update Time : Sat Feb 11 15:10:31 2017 > State : active > Active Devices : 4 > Working Devices : 4 > Failed Devices : 0 > Spare Devices : 0 > > Layout : near=2 > Chunk Size : 512K > > Name : localhost.localdomain:2 (local to host > localhost.localdomain) > UUID : ea253255:cb915401:f32794ad:ce0fe396 > Events : 1818029 > > Number Major Minor RaidDevice State > 4 8 35 0 active sync set-A writemostly > /dev/sdc3 > 5 8 19 1 active sync set-B /dev/sdb3 > 7 8 51 2 active sync set-A writemostly > /dev/sdd3 > 6 8 3 3 active sync set-B /dev/sda3 > _______________________________________________ > kernel mailing list -- kernel@xxxxxxxxxxxxxxxxxxxxxxx > To unsubscribe send an email to kernel-leave@xxxxxxxxxxxxxxxxxxxxxxx > _______________________________________________ kernel mailing list -- kernel@xxxxxxxxxxxxxxxxxxxxxxx To unsubscribe send an email to kernel-leave@xxxxxxxxxxxxxxxxxxxxxxx
