From mboxrd@z Thu Jan 1 00:00:00 1970 From: Stan Hoeppner Subject: Re: Linear device of two arrays Date: Sat, 8 Jul 2017 16:24:10 -0500 Message-ID: <5afd5cea-06b8-8524-e4f5-8534f23bd714@hardwarefreak.org> References: <20170705214250.0ea99538@natsu> <595D2ADA.8010907@youngman.org.uk> Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: Sender: linux-raid-owner@vger.kernel.org To: veljko3@gmail.com, linux-raid@vger.kernel.org, neilb@suse.com List-Id: linux-raid.ids On 07/08/2017 05:26 AM, Veljko wrote: > On Sat, Jul 8, 2017 at 12:52 AM, Stan Hoeppner wrote: >> On 07/07/2017 03:26 PM, Veljko wrote: >>> I just noticed that I replied to Wol insted to list. >>> >>> On Wed, Jul 5, 2017 at 8:07 PM, Wols Lists >>> wrote: >>>> On 05/07/17 17:42, Roman Mamedov wrote: >>>>> On Wed, 5 Jul 2017 17:34:09 +0200 >>>>> Veljko wrote: >>>>> >>>>>> Hello, >>>>>> >>>>>> I have a RAID10 device which I have formated using the mkfs.xfs >>>>>> defaults (Stan helped me with this few years back). I reached 88% >>>>>> capacity and it is time to expand it. I bought 4 more drives to create >>>>>> another RIAD10 array. I would like to create linear device out of >>>>>> those two and grow XFS across the 2nd device. How can this be done >>>>>> without loosing the existing device's data? I would also like to add a >>>>>> spare HDD. Do I have to have a separate spare HDD for each array or >>>>>> one can be used by both of them? >>>>> Why make another RAID10? With modern versions of mdadm and kernel you >>>>> should >>>>> be able to simply reshape the current RAID10 to increase the number of >>>>> devices used from 4 to 8. >>>>> >>>>> >>>> I was thinking of replying, but isn't that not possible for some >>>> versions of RAID-10? >>>> >>>> My feeling was, if you can't just add drives to the existing raid 10, >>>> create a new one which you can expand, migrate the fs across (btrfs >>>> would let you do that live, I believe, so xfs probably can too), then >>>> you can scrap the old raid-10 and add the drives into the new one. >>>> >>>> Cheers, >>>> Wol >>> >>> Thanks for your input, Roman and Wol. >>> >>> Expanding existing RAID is one of the options, but I was advised by >>> Stan Hoeppner to do it this way and I tend to believe him on this >>> subject. With my metadata heavy backup workload, this will provide >>> better performance. >>> >>> So my question is still, how can an existing array be added to linear >>> device, and it's file system expanded over the second array. >> For this to work the existing RAID10 array must already be a member of a >> linear device with one component device. If this linear array already >> exists then you could add another RAID10 array to the linear device. If you >> currently have an XFS filesystem sitting atop a 'bare' RAID10 then I don't >> believe the linear option will work for you. Thus I'd tend to agree with >> others that reshaping your current RAID10 is the best option. >> >> My apologies if I wasn't clear in my previous advice. >> >> Stan > Here is your previous advice: > "Do not use LVM. Directly format the RAID10 device using the mkfs.xfs > defaults. mkfs.xfs will read the md configuration and automatically > align the filesystem to the stripe width. > > When the filesystem reaches 85% capacity, add 4 more drives and create > another RAID10 array. At that point we'll teach you how to create a > linear device of the two arrays and grow XFS across the 2nd array." > > From this I concluded that it is possible to create linear device > using existing array, but since it is not the case, I'll just have to > create new array, move data to it, than add first array to a new > linear device (1 member), copy my data to it, and than join second > device to it. I wanted to avoid all this copying but will have to do > it. Than I will add one drive to spare-group both arrays will be a > members of, as advised by Andreas. Does this sound OK? Yes. Although, I was hoping Neil Brown would chime in here. I'm not entirely sure that you can't do this the way I originally mentioned. > Regards, > Veljko > -- > To unsubscribe from this list: send the line "unsubscribe linux-raid" in > the body of a message to majordomo@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html