On Sun, 5 Mar 2017 16:31:24 -0500, James Blachly wrote:
Thanks Yuri. This solution is much cleaner inasmuch as with your
feature, my patch to OpenZFS code wouldn’t have to include check for
every possible non rotational media type, and as well this property
could potentially be useful elsewhere. If you want to get reviews on
this I can rebase and update my patch to query this property instead.
OK, I'll post separate review for this.
On Mar 5, 2017, at 4:23 PM, Yuri Pankov <[email protected]
<mailto:[email protected]>> wrote:
On Sun, 5 Mar 2017 23:29:24 +0300, Yuri Pankov wrote:
On Sun, 5 Mar 2017 15:09:39 -0500, James Blachly wrote:
ZFS on Linux has had a feature "Disable LBA weighting on SSD" since
August 2015:
http://open-zfs.org/wiki/Features#Disable_LBA_Weighting_on_files_and_SSDs
https://github.com/zfsonlinux/zfs/commit/fb40095f5f0853946f8150481ca22602d1334dfe
Because we have the driver property "device-solid-state" we can port
this over. In addition, we should add detection for virtio vioblk
device, which should also not use LBA weighting.
On linux, block devices have a "non-rotational" property, so this is
a one liner in vdev_disk.c:
v->vdev_nonrot = blk_queue_nonrot(bdev_get_queue(vd->vd_bdev));
We do not, so the checks are a little bit more cumbersome but doable
(check device-solid-state != 0 and inquiry-vendor-id==Virtio separately)
QUESTIONS
1. Linux has a non rotational property for block devices. Should we?
By moving this out of ZFS it could be used in other places. Besides
SSD, this property would apply to zvols, Virtio disks, and
potentially in the future, network block devices (e.g. ceph)
2. Is there a better or more preferred way to check for a Virtio
vioblk device besides checking inquiry-vendor-id ?
3. Since this is a straight port of all but the code in vdev_disk.c,
I did not add copyright messages. This will cause git pbchk to
gripe. How is this typically handled?
4. OpenZFS developers: your repo is out of sync with illumos-gate; I
don’t know how to create a PR on github that does not also include
other commits not yet merged into your fork. Pointers appreciated.
Make changes against cloned openzfs repository, but push them as a
branch into your illumos-gate fork, eg:
git clone [email protected]:openzfs/openzfs.git
git remote add illumos <your-fork>
<make changes>
git push illumos master:<new-branch>
and then create PR from that branch.
---
Issue: https://www.illumos.org/issues/7938
Webrev: http://cr.illumos.org/~webrev/jblachly/zfs_lba_weighting/
Git commit:
https://github.com/jblachly/illumos-gate/commit/863ed00ba3278bfec58a0edb504ad484fac0c10b
WRT the change itself - please correct me if I'm wrong, but looks like
all possible rotational disk are driven by sd(7D), so if the parent
isn't sd, it's not rotational - blkdev, which is yours "Virtio", any
others?
For the sd itself, we could enhance the sd_check_solid_state() to set
non-rotational device property is "Block Device Characteristics" VPD
reports RPM == 0 (for SSDs RPM == 1) - e.g., for pvscsi disks I'm
getting RPM == 0, same would go for iscsi, etc.
Here's a quick attempt at doing just that:
http://cr.illumos.org/~webrev/yurip/il-dev-rot/
for virtual disk:
# prtconf -v /dev/dsk/c2t0d0 | grep -A1
'device-rotational\|device-solid-state\|inquiry-product-id'
name='device-solid-state' type=int items=1 dev=none
value=00000000
name='device-rotational' type=int items=1 dev=none
value=00000000
--
name='inquiry-product-id' type=string items=1
value='Virtual disk'
for spinning rust:
# prtconf -v /dev/dsk/c0t5000C5004CB22B0Bd0 | grep -A1
'device-rotational\|device-solid-state\|inquiry-product-id'
name='device-solid-state' type=int items=1 dev=none
value=00000000
name='device-rotational' type=int items=1 dev=none
value=00000001
--
name='inquiry-product-id' type=string items=1
value='ST3450857SS'
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