/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
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 : activeActive Devices : 4 Working Devices : 4 Failed Devices : 0 Spare Devices : 0
Layout : near=2 Chunk Size : 512K Name : localhost.localdomain:2 (local to hostlocalhost.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@lists.fedoraproject.org To unsubscribe send an email to kernel-leave@lists.fedoraproject.org
Stupid me forgot half of what I wanted to write:
On 11.02.2017 16:15, Thorsten Leemhuis wrote:
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 forgot to write here: Some of those links will show that others (just like you and me) found that writemostly doesn't work that well. I had similar results and stopped using it. Iirc upstream added it as a quick hack that in the end didn't work that well, so it hasn't a high priority there and it's a known problem. Got that impression after reading some mails in the archives when I was looking into writemostly a year or two ago, but can't find those right now :-/
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 : activeActive Devices : 4 Working Devices : 4 Failed Devices : 0 Spare Devices : 0
Layout : near=2 Chunk Size : 512K Name : localhost.localdomain:2 (local to hostlocalhost.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@lists.fedoraproject.org To unsubscribe send an email to kernel-leave@lists.fedoraproject.org
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 : activeActive Devices : 4 Working Devices : 4 Failed Devices : 0 Spare Devices : 0
Layout : near=2 Chunk Size : 512K Name : localhost.localdomain:2 (local to hostlocalhost.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
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