Re: [HPDD-discuss] Lustre Disk to Disk MDS Backup Question

> -----Original Message----- > From: hpdd-discuss-bounces(a)lists.01.org [mailto:hpdd-discuss- > bounces(a)lists.01.org] On Behalf Of Kumar, Amit > Sent: Wednesday, April 10, 2013 4:13 PM > To: Dilger, Andreas; Pablo Escobar > Cc: hpdd-discuss(a)lists.01.org > Subject: Re: [HPDD-discuss] Lustre Disk to Disk MDS Backup Question > > Hi Andreas thank you for answering these questions. But I guess there is one > more missing element that I don't get it: > > The backup device that you backup your MDS/MDT/MGS to : did you create > it with mkfs.ext3 or mkfs.lustre ? Hi Amit, The answer is neither. > In other works can I do a backup using dd to an ext3 file system device or > not? When using 'dd' you are writing to a block device - there is no need to create a file system. If you did have a file system on the device, the 'dd' output would overwrite it. Think of 'dd' as writing to a block device much the same as 'mkfs' writes to a block device (whereas commands like 'cp' and 'mv' write to the file system on the block device.) -Brett > > Best Regards, > Amit > > > > > -----Original Message----- > From: Dilger, Andreas [mailto:andreas.dilger@intel.com] > Sent: Wednesday, April 10, 2013 4:44 PM > To: Pablo Escobar > Cc: Kit Westneat; Kumar, Amit; hpdd-discuss(a)lists.01.org > Subject: Re: [HPDD-discuss] Lustre Disk to Disk MDS Backup Question > > On 2013/09/04 4:54 PM, "Pablo Escobar" <pescobar001(a)gmail.com&gt; wrote: >> could you post or link some more detailed technical docs about how you >> snapshot and backup the mds? >> >> My main doubt is that if I do an snapshot and backup of mds, for >> example, on friday and during the weekend the client nodes modify the >> filesytem and then I need to recover on monday. wouldn´t it be >> inconsistent? would be possible to recover the data in this situation? >> Is there any docs about this recover procedure? > > Snapshots are done using normal LVM commans "lvcreate -s" to create a > snapshot of the MDT device. I'm sure there are equivalent dmadmin > commands to do the same? > > Then, simple "dd" to copy the MDT snapshot to a separate block device > (actually, two separate devices on alternate days, and one only manually). > The MDT is small, and the backup devices do not need to have good IOPS > performance, just simple 5400-RPM SATA is enough for streaming "dd" > copies. Since the MDT is a single point of failure for all of the data in the > filesystem, it makes sense to keep this backed up even if the data is too large > to back up. > > This is only intended for emergency recovery, since I also test experimental > patches on my home system at times, but it holds real data that the rest of > my family cares about (music collection, all of the TV we watch, etc). > > Yes, if there is a recovery from the backup MDT copy, the newer files are > lost, but that is true of any backup system. In theory it would be possible to > reconstruct the new files from their OST objects using lfsck (in my case > mostly just newly-recorded TV shows), but that has not been a primary > concern compared to being able to recover the rest of the filesystem. > > Cheers, Andreas > >> 2013/4/10 Dilger, Andreas <andreas.dilger(a)intel.com&gt; >> >> On 2013/09/04 9:47 AM, "Kit Westneat" <kwestneat(a)ddn.com&gt; wrote: >> >>> You should do that in order to get a clean image. If you don't, then >>> you are more likely to get an inconsistent image. Of course, an >>> inconsistent image is better than no image, but ideally you'd want to get a > clean one. >> >> >> Or, since this is a device mapper device, you can create a snapshot, >> and then use "dd" from the MDS snapshot (which should be consistent). >> That's what I do for my MDS backups, and it has saved me a couple of >> times. >> >> Cheers, Andreas >> >>> On 04/09/2013 11:33 AM, Kumar, Amit wrote: >>>> Hi Kit >>>> >>>> This is good to know. Do I still need to shutdown the lustre FS? And >>>> Umount the devices? >>>> >>>> Thank you >>>> Amit >>>> >>>> Sent from my iPhone >>>> >>>> On Apr 9, 2013, at 10:27 AM, "Kit Westneat" >>>> <kwestneat@ddn.com<mailto:kwestneat@ddn.com>> wrote: >>>> >>>> Hi Amit, >>>> >>>> If you are doing a disk to disk backup, and the size of the backup >>>> disk is >= the main disk, I would just use dd and not worry about >>>> formatting the disk beforehand. The dd will replicate the filesystem >>>> structure exactly, so there's no need to mkfs. I would do something >>>> like 'dd >>>> if=/dev/dm-0 of=/dev/dm-2 bs=1M'. >>>> >>>> - Kit >>>> >>>> On 04/09/2013 02:40 AM, Kumar, Amit wrote: >>>> I forgot to paste the link I referenced to perform backup: here it is: >>>> http://wiki.lustre.org/manual/LustreManual18_HTML/BackupAndRestor > e.ht >>>> ml Any thoughts on this will be very helpful! >>>> Thank you, >>>> Amit >>>> >>>> From: >>>> hpdd-discuss-bounces@lists.01.org<mailto:hpdd-discuss- > bounces(a)lists.0 >>>> 1.o >>>> r >>>> g> [mailto:hpdd-discuss-bounces@lists.01.org] On Behalf Of Kumar, >>>> g> Amit >>>> Sent: Monday, April 08, 2013 12:47 PM >>>> To: HPDD-discuss@lists.01.org<mailto:HPDD-discuss@lists.01.org> >>>> (HPDD-discuss@ml01.01.org<mailto:HPDD-discuss@ml01.01.org>) >>>> Subject: [HPDD-discuss] Lustre Disk to Disk MDS Backup Question >>>> >>>> Dear All, >>>> >>>> ³Version 1.8² >>>> >>>> We have both MGS & MDT mounted on two different block devices. >>>> Now I would like to perform a disk to disk backup of both of these >>>> block devices to another set of block devices. >>>> >>>> Although this link tells me how to perform that. There are some >>>> missing things that I want to understand before I can perform this >>>> backup >>>> >>>> We have two devices /dev/dm-1 & /dev/dm-0 mounted as /mgs and > /mdt >>>> respectively. >>>> >>>> Now I have two more devices /dev/dm-2 & /dev/dm-3 which I want to >>>> mount it as /mgs-backup and /mdt-backup and then perform the disk to >>>> disk backup. Because we are not backing up any of the metadata right > now. >>>> >>>> Here is where I get lost: when I want to make the lustre file system >>>> it asked me if the device is going to be an mgs or mdt or it will be >>>> combined. Now that I already have an /mgs and /mdt partition on this >>>> node what will happen if I make new block device to be an mgs and mdt >>>> partition, will this conflict with the existing ?????? >>>> Or can I just make the new devices just an ext3 partition and still >>>> be able to make a disk to disk copy of meta data that I can restore >>>> when needed. > > > Cheers, Andreas > -- > Andreas Dilger > > Lustre Software Architect > Intel High Performance Data Division > > > _______________________________________________ > HPDD-discuss mailing list > HPDD-discuss(a)lists.01.org > https://lists.01.org/mailman/listinfo/hpdd-discuss -- Brett Lee Sr. Systems Engineer Intel High Performance Data Division