Am 11.02.2017 um 16:15 schrieb Thorsten Leemhuis:
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/
i really have no ieda what you try to tell me
please look again at the subject and the mdadm output because *they are*
set "writemostly" but there is way too much read-io on the HDD's
> 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