Real Time Mirroring of a NAS
Hi, I'm looking for a way to create a real-time mirror of a NAS. In other words, say I have a 5.5 TB NAS (3ware 16-drive array, RAID-5, 500 GB drives). I want to mirror it in real time to a completely separate 5.5 TB NAS. RSYNCing in the background is not an option. The two NAS boxes need to hold identical data at all times. It is NOT necessary that the data be accessed from both NAS boxes simultaneously. One is simply a backup of the other. I guess one option might be to use Redhat's Global File System (GFS). Although there seems to be an 8TB limit for a GFS filesystem, which could be an issue down the road. But would the following approach work: Can I export NAS B as a SAN or ISCSI target, connect the two machines with, say, mryinet cards or 10 GbE TOE cards, mount the NAS B volume on NAS A, and create a RAID-1 mirror of the two volumes? Is this kind of thing done? Andy Liebman - To unsubscribe from this list: send the line unsubscribe linux-raid in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html
Re: Real Time Mirroring of a NAS
On Fri, 7 Apr 2006 at 6:47am, andy liebman wrote I'm looking for a way to create a real-time mirror of a NAS. In other words, say I have a 5.5 TB NAS (3ware 16-drive array, RAID-5, 500 GB drives). I want to mirror it in real time to a completely separate 5.5 TB NAS. RSYNCing in the background is not an option. The two NAS boxes need to hold identical data at all times. It is NOT necessary that the data be accessed from both NAS boxes simultaneously. One is simply a backup of the other. I guess one option might be to use Redhat's Global File System (GFS). Although there seems to be an 8TB limit for a GFS filesystem, which could be an issue down the road. I don't have any experience with it, but I've often seen DRBD mentioned for just this sort of situation. I'd look into that. -- Joshua Baker-LePain Department of Biomedical Engineering Duke University - To unsubscribe from this list: send the line unsubscribe linux-raid in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html
Re: accessing mirrired lvm on shared storage
Matthias I have currently four clusters which mirror shared storage. I've always pay great attention not to have an array active on both cluster nodes. I can imagine data corruption would happen soon or late. Unfortunately md lacks the ability to mark an array as used/busy/you_name_it. Sometime ago I asked on this list for such an enhancement (see thread with subject Question: array locking, possible). Although I managed (with great help from few people on this list) to attract Neil's attention, I couldn't fine enough arguments to convince him to put this topic on hist TO-DO list. Neil, you see the constantly growing number of potential users of this feature? ;-) Regards, Chris PS Matthias, just curious, you don't have FC failover, right? On Thu, 06 Apr 2006 20:19:53 +0200 Matthias Eble [EMAIL PROTECTED] wrote: Hi all, I've got an extended setup whith two Systems, each with two FC cards. Every card is connected to a seperate disk array (so one system accesses two arrays). The other node has access to the same two arrays (standby). The active server mirrors the data (4 LUNs) between the two arrays via md. On top is a LVM physical volume. The other system is meant to be booted but not acessing the VGs. My question is, if it is possible to let both systems set up the md mirror without corrupting the data? Is there any data written even when the VGs are not taken active? I think I remember that LVM refuses to activate volumegroups which are active on another system, right? This would save me from caring about IO fencing. thanks for your help in advance.. matthias - To unsubscribe from this list: send the line unsubscribe linux-raid in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html - To unsubscribe from this list: send the line unsubscribe linux-raid in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html
Re: Partitioning md devices versus partitioining underlying devices
andy Here's a concrete example. I have two 3ware RAID-5 arrays, each andy made up of 12 500 GB drives. When presented to Linux, these are andy /dev/sda and /dev/sdb -- each 5.5 TB in size. andy I want to stripe the two arrays together, so that 24 drives are andy all operating as one unit. However, I don't want an 11 TB andy filesystem. I want to keep my filesystems down below 6 TB. Why? What are you issues with large filesystems? I assume this is related to your NAS - NAS mirror question as well. Also, what will you do if a single controller fails? Or do you care? andy 1) partition the 3ware devices to make /dev/sda1, /dev/sda2, /dev/sdb1 andy and /dev/sdb2. Then I can create TWO md RAID-0 devices -- /dev/sda1 + andy /dev/sdb1 = /dev/md1, /dev/sda2 + /dev/sdb2 = /dev/md2 andy OR andy 2) create /dev/md1 from the entire 3ware devices -- /dev/sda + /dev/sdb andy = /dev/md1 -- and then partition /dev/md1 into two devices. The general plan I would use is to start at the low level and go from: /dev/sda1 - md1 - LVM - partition But the question is whether to use Hardware RAID5, or Software RAID5. If the data is really important, I'd probably think seriously about using Neil's RAID6 patches because a single disk failure takes so long to re-sync and recover from, and RAID6 helps close that gap alot. So I think I'd probably just ignore a controller failing issue, since I'm mirroring the data to a totally seperate device, and just build a single large RAID6 device with a single hot spare disk. So you'd have 21 x 500GB worth of data. Heck, I'd also look into getting a server with multiple PCI busses and getting non-3ware controllers across more busses since I'd get better performance. But the 3ware should hopefully hide single disk hot-swap issues better. It's a tradeoff and time for testing. Anyway, try to put each 3ware onto it's own PCI bus if you can. So, ontop of that huge RAID6 volume, I'd stick LVM and then carve out the PVs - LVs and make the filesystem I want onto the LVs. andy The question is, are these essentially equivalent alternatives? andy Is there any theoretical reason why one choice would be better andy than the other -- in terms of security, performance, memory andy usage, etc. If you add in LVM to the mix, I think they are both equivilent, since you use LVM as an interface layer to hide the details of the lower layers from the filesystem. With LVM you can add/move/delete PVs (Physical Volumes) from a system and move data around with the system live. This would allow you to do a quick shutdown to add new hardware/disks and then bring up the system. With the system live and serving data, you can then build new PVs, add them into LVM and then move data from old controllers/disks to new disks, all while serving data and keeping up redundancy. It's really cool. You do take some performance hit while doing this, since you are copying lots and lots of data around, but it's not bad at all. Look for a stable filesystem which allows you to resize it while mounted. I think XFS lets you do this, but double check. John - To unsubscribe from this list: send the line unsubscribe linux-raid in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html
Re: Real Time Mirroring of a NAS
Hello andy, al Can I export NAS B as a SAN or ISCSI target, connect the two machines Am I right in the assumption that your NASes are Linux boxes? :) Did you take a look at Linux Network block devices (nbd/enbd)? They might be what you need: you'd get a raw device on one of the servers to use in a mirror along with a local device. The NBD page mentioned some setups for high-availability services where an active server clones itself to a backup server and vice-versa, whichever was active most recently. I'm not sure about performance though... al with, say, mryinet cards or 10 GbE TOE cards, mount the NAS B volume on al NAS A, and create a RAID-1 mirror of the two volumes? Is this kind of al thing done? Are you sure you need 10GbE? My experience with a 10-drive 3Ware 8506 array in RAID5 shows that reads from it usually fit in 500-700Mbit/s. And it's a very busy popular fileserver, so I guess it's close to the hardware limits of our array. -- Best regards, Jim Klimovmailto:[EMAIL PROTECTED] - To unsubscribe from this list: send the line unsubscribe linux-raid in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html
Re: Real Time Mirroring of a NAS
I'm looking for a way to create a real-time mirror of a NAS. In other words, say I have a 5.5 TB NAS (3ware 16-drive array, RAID-5, 500 GB drives). I want to mirror it in real time to a completely separate 5.5 TB NAS. RSYNCing in the background is not an option. The two NAS boxes need to hold identical data at all times. It is NOT necessary that the data be accessed from both NAS boxes simultaneously. One is simply a backup of the other. I don't have any experience with it, but I've often seen DRBD mentioned for just this sort of situation. I'd look into that. Linux NBD (and md on top) is a simpler solution for the same thing. I'd look into that also :) - To unsubscribe from this list: send the line unsubscribe linux-raid in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html
Re: Real Time Mirroring of a NAS
[EMAIL PROTECTED] wrote: Hello andy, al Can I export NAS B as a SAN or ISCSI target, connect the two machines Am I right in the assumption that your NASes are Linux boxes? :) Did you take a look at Linux Network block devices (nbd/enbd)? They might be what you need: you'd get a raw device on one of the servers to use in a mirror along with a local device. The NBD page mentioned some setups for high-availability services where an active server clones itself to a backup server and vice-versa, whichever was active most recently. I'm not sure about performance though... al with, say, mryinet cards or 10 GbE TOE cards, mount the NAS B volume on al NAS A, and create a RAID-1 mirror of the two volumes? Is this kind of al thing done? Are you sure you need 10GbE? My experience with a 10-drive 3Ware 8506 array in RAID5 shows that reads from it usually fit in 500-700Mbit/s. And it's a very busy popular fileserver, so I guess it's close to the hardware limits of our array. Thanks for your reply, and the suggestions of others. I'm going to look into both NBD and DRBD. Actually, I see that my idea to export an iSCSI target from Server B, mount it on A, and just create a RAID1 array with the two block devices must be very similar to what DRBD is doing, but my guess is that DRBD, with it's heartbeat signal, is probably more robust at error handling. I'd love to hear from somebody who has experience with DRBD. By the way, I use 3ware 9550SX cards. On a 16 drive RAID-5 SATA array, I can get sequential reads that top 600 MBs/sec. That's megabytes, not megabits. And write speeds are close to 400 MB/sec with the new faster on-board XOR processing. And random reads are at least 200 MB/sec. So, 10 GbE is a must, really. Andy - To unsubscribe from this list: send the line unsubscribe linux-raid in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html
RHEL3 kernel panic with md
I appear to have a corrupt file system and now it is mirrored. LOL. I am running Redhat Enterprise 3 and using mdtools. I booted from the install media iso and went into rescue mode. RH was unable to find the partitions automatically but after exiting into bash i can run fdisk -l and i see all of the partitions. I know this is sparse info but would any of the group be able to give the best approach to getting them mounted and fsck'd? Thank you in advance Colin - To unsubscribe from this list: send the line unsubscribe linux-raid in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html
