From mboxrd@z Thu Jan 1 00:00:00 1970 From: Bill Davidsen Subject: Re: Sleepy drives and MD RAID 6 Date: Thu, 14 Aug 2014 14:10:15 -0400 Message-ID: <53ECFB87.3010700@tmr.com> References: <20140812092901.60f007e6@natsu> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <20140812092901.60f007e6@natsu> Sender: linux-raid-owner@vger.kernel.org To: linux-raid@vger.kernel.org List-Id: linux-raid.ids Roman Mamedov wrote: > On Mon, 11 Aug 2014 18:03:17 -0700 > Adam Talbot wrote: > >> I need help from the Linux RAID pros. >> >> To make a very long story short; I have a 7 disk in a RAID 6 array. I >> put the drives to sleep after 7 minutes of inactivity. > > It is well known that repeatedly spinning a drive down/up is absolutely the > worst possible thing you can do to it, from a long term reliability standpoint. > So my personal suggestion would be to reconsider if you really want this. The > power consumption from 7 spinning drives with no access should be no higher > than 60-70 watt; IMHO saving that amount, is not something that's worth risking > your disks and data for. > Unless you live in someplace really cold, there's the cost of pumping that heat out of the room. Running A/C can almost double your power cost, and running the room hot shortens your component life. In other words there's more cost than the power for most people. Even if my hardware can run at 90F, I can't. There appears to be a partial solution, get a small SDD (<$100) and put the journal on it. Get two, run RAID1 if you must. Then configure the system to write the journal with all data (data=journal), and the write will be really fast, even if they don't fully complete for a minute or so. Doesn't help reads, of course. Turns the journal into cache, sort of. I have the feeling that sequential spin is an option in a driver, but I can't remember or quickly find where. I say this because I had to set it on one machine I had, spinning up the whole array at one caused the power supply to overload, and until I could get a bigger one which would fit I set an option. That was long enough that I can't remember where I found that. Turn it off and all seven drives will ask for power at once, which probably isn't a great thing, but not my system. -- Bill Davidsen "We have more to fear from the bungling of the incompetent than from the machinations of the wicked." - from Slashdot