Hi, The attached project has been proposed to the OpenSolaris PM community. thanks, -jane -- This message posted from opensolaris.org -------------- next part -------------- Storage PM Project ================= Currently, the main challenges in power managing disks on server platforms are the issues of latency and reliability: * Latency, as defined by time to first data access, is incurred when powering up a disk to put it in service. While latency for a disk in operation is measured in milliseconds, a disk may take seconds or even tens of seconds to come on line if it needs to be powered up and spin up. * Reliability is an issue in multiple contexts. With RAID configurations, which guard against random media errors, all disks in the RAID group must be online or offline -- it is not possible to achieve power savings by powering down some of the drives. In addition, excessive head load/unload operations (to save a limited amount of power) can cause disk failure over time. Any disk power management must take this into account. With the invention of ZFS, the latency issue and part of the reliability issue can now be addressed. Specifically, ZFS''s baked in Volume Manager and its software RAID-Z feature are among the key features responsible for a possible breakthrough in the area of power managing server disks. This project is the first step to enabling power savings from more intelligent management of storage. It offers potential substantial power savings with minimal impact to storage I/O performance for server or storage platforms utilizing ZFS. The project positions ZFS as Resource Manager that interacts with Solaris''s Common Power Management software to provide shrink-to-fit Elastic policy on non-virtualized platforms. Future projects will provide the above functionality in virtualized environments, and moving furthur on, to explore opportunities to provide similar a feature set on non-ZFS filesystems. Modern SAS and SATA disks provide a variety of power states enabling a reduction in power consumption. In some cases, these reduced power consumption states allow data to remain on line for access at lower throughput and/or higher latency (by slowing down head seek, for example). In most cases, however these states result in the data stored on the disk being rendered inaccessible until the host takes action to return the disk to normal operation. In order to allow the disk Resource Manager (i. e. ZFS in the current project phase) to regulate the disk power consumption, it must be possible for the software to: * Identify the storage devices it is using (this information is already available by other means). * Identify the set of power saving states and their characteristics (e. g. power requirement at each different state, time to bring online). Note that different storage devices in the same system may offer different power states, so it must be possible to discover the power states available for each storage device in use. * Identify the state that a storage device is currently in. * Request that the device place itself in a specified low power state. * Request that the device recover from the reduced power state into the normal functional state. The specific components that this project will deliver are as follows: * Provide infrastructure that allows the disk driver and SATA framework to retrieve industry-standard SAS or SATA power state information from disks, set and change disk power states, and report information on available power states to higher levels of software. In this phase of the project, this interface will only function in a non-virtualized environment; operation in virtualized environments such as xVM or LDoms will be deferred to a future project. * Provide a Resource Power Manager (RPM) software layer that interacts with the Resource Manager and existing PM framework to provide the Resource Manager ability to adjust the power states of disks to achieve power savings. * Enhance ZFS to provide Elastic mode power savings by setting disks not currently in use to a lower power state and by optionally configuring its available storage to minimize the number of drives in use.
On Mon, Nov 03, 2008 at 02:54:10PM -0800, Yuan Chu wrote: Hi,> a disk may take seconds or > even tens of seconds to come on line if it needs to be powered up > and spin up.Yes - I really hate this on my U40 and tried to disable PM for HDD[s] completely. However, haven''t found a way to do this (thought /etc/power.conf is the right place, but either it doesn''t work as explained or is not the right place). HDD[s] are HITACHI HDS7225S Revision: A9CA Any hints, how to switch off PM for this HDD? Regards, jel. -- Otto-von-Guericke University http://www.cs.uni-magdeburg.de/ Department of Computer Science Geb. 29 R 027, Universitaetsplatz 2 39106 Magdeburg, Germany Tel: +49 391 67 12768
Not wanting to hijack this thread, but... I''m a simple man with simple needs. I''d like to be able to manually spin down my disks whenever I want to... Anyone come up with a way to do this? ;) Nathan. Jens Elkner wrote:> On Mon, Nov 03, 2008 at 02:54:10PM -0800, Yuan Chu wrote: > Hi, > >> a disk may take seconds or >> even tens of seconds to come on line if it needs to be powered up >> and spin up. > > Yes - I really hate this on my U40 and tried to disable PM for HDD[s] > completely. However, haven''t found a way to do this (thought > /etc/power.conf is the right place, but either it doesn''t work as > explained or is not the right place). > > HDD[s] are HITACHI HDS7225S Revision: A9CA > > Any hints, how to switch off PM for this HDD? > > Regards, > jel.
Jane.Chu at Sun.COM
2008-Nov-05 16:22 UTC
[zfs-discuss] FYI - proposing storage pm project
Nathan Kroenert wrote:> Not wanting to hijack this thread, but... > > I''m a simple man with simple needs. I''d like to be able to manually > spin down my disks whenever I want to... > > Anyone come up with a way to do this? ;)You can do that, but you''d need to write your own user application to issue an PM_DIRECT_PM ioctl command. See pm(7D) man page. Personally I wouldn''t recommand this partly because I''ve never heard of any practice of it and am unsure of potential consequences. -jane> > Nathan. > > Jens Elkner wrote: > >> On Mon, Nov 03, 2008 at 02:54:10PM -0800, Yuan Chu wrote: >> Hi, >> >> >>> a disk may take seconds or >>> even tens of seconds to come on line if it needs to be powered up >>> and spin up. >> >> >> Yes - I really hate this on my U40 and tried to disable PM for HDD[s] >> completely. However, haven''t found a way to do this (thought >> /etc/power.conf is the right place, but either it doesn''t work as >> explained or is not the right place). >> >> HDD[s] are HITACHI HDS7225S Revision: A9CA >> >> Any hints, how to switch off PM for this HDD? >> >> Regards, >> jel. >
Nathan Kroenert wrote:> Not wanting to hijack this thread, but... > > I''m a simple man with simple needs. I''d like to be able to manually spin > down my disks whenever I want to... > > Anyone come up with a way to do this? ;) >For those disks that support it, luxadm stop /dev/rdsk/... has worked for the past 10 years or so. -- richard