On Tue, 2008-08-12 at 23:00 +0300, Alex wrote: > > I mean that i'm exporting via iscsi a block device
Ahhh. Now that's nomenclature I'm grasping. :-) > In this case is and entire hard disk, 120GB large, > named for simplicity volX (vol1, vol2... vol8) because i have 8 computers > doing this. Right. So you have 8 iscsi disks. > For example could be a GFS shared volume over volX. Here on lustre i don't > know ... You tell me ... These 3 servers are still unclear to me. What do you see their function as being? Would they be the Lustre filesystem servers to which Lustre clients go to get access to the shared filesystem composed of the 8 iscsi disks? If so, then it sounds like your 3 servers are looking to create a Lustre filesystem with the 8 iscsi disks. This is doable but not a typical scenario. You would probably dedicate one of the 8 targets to the MDT and the other 7 as OSTs. > I don't know lustre. I asked about. I just want to know if is possibile ... > If > the answer is yes, my question is: who will be MDS and WHO will be OSSes. How > MANY MDS and HOW MANY OSSes I NEED in order to obtain what i want! Well, from your explanation above I would imagine you would use your three servers to create 1 active MDS and 2 active OSSes with each OSS hosting 4 and 3 OSTs respectively. You could pair the machines so that one would pick up the slack of a failed machine in a failover event. Something like: Server 1 Server 2 Server 3 Primary MDS Primary OSS1 Primary OSS2 Backup OSS1 Backup OSS2 Backup MDS > Can you run Lustre on LVM volumes, software RAID, etc? > > Yes. You can use any Linux block device as storage for a backend Lustre > server > file system, including LVM or software RAID devices. > [end snip] Oh, hrm. You want no SPOF. Given that you have 8 targets all in 8 different machines, I'm not quite sure how you are going to achieve that. I suppose you could mirror two of the 8 iscsi devices for the MDT and RAID5/6 the remaining 6 iscsi devices into a single volume. You could then have 1 of your 3 machines be Primary MDS, the other Primary OSS and the third backup for both of the first. It does seem a bit wasteful to have a single machine doing nothing but waiting for failure but this is frequently the case when you are working on the low end with so little. > So, for me, reading this, is very clear without being an expert that lustre > support BLOCK DEVICES in any RAID/LVM configuration... Indeed. > Also lustre, can work > with my iscsi block devices /dev/sd[a-h] ... Sure. But you will have to build your redundancy on those devices before giving them to Lustre. Lustre provides no redundancy itself and relies on the underlying block device to be redundant. > This is not clear at all... Generally speaking ext3 is a local file system > (used on one computer). Reading FAQ, didn't find an answer, so i asked > here... Right. It is in fact too much information for the Lustre beginner. You should just be told that Lustre operates on and manages the block device. That it does so through ext3 only serves to confuse the Lustre beginner. Later when you have a better grasp on the architecture it might be worthwhile understanding that each Lustre server does it's management of the block device via ext3. So please, don't worry about the traditional uses of ext3 and confuse it's limitations with Lustre. Lustre simply didn't want to invent a new on-disk management library and used ext3 for it. > No i can't ignore ... I want to be sure that ext3 used by lustre is a > clustered file system. Well, you are just going to have to take my word for it or start digging deeper into the architecture of Lustre to be sure of that. Beyond what I've already explained I'm not going to get any deeper into the internals of Lustre. > Redhat NEVER indicated their ext3 as file system for > clusters. First of all, ext3 is not RedHat's. Second, ext3, in and of itself is not for clusters, this is true. > So, if lustre's ext3 file system > is clustered, why nobody add a note to the FAQ about that: "we are using a > patched ext3 version, which differ by redhat ext3 because it support cluster > file systems like GFS"... Because it's not like that. As I have said, we simply use ext3 as a storage mechanism. b.
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