I'm trying to create my own SAN out of existing hardware. I have four identical NAS devices. Each one has four 1 TB drives that they do RAID-5 across. On each NAS I have created a 1 TB iSCSI share. I have another linux server that connects to each iSCSI target. On this server I have created a RAID 10 array of these iSCSI devices. I then plan to share this array out via NFS. With this setup I could survive several hard drive failures and even lose a whole NAS. But I also want to have a second NFS server as well. It sounds like my second server should be able to connect to the iSCSI targets without a problem but I'm not sure what will happen when I try to create the RAID 10 array.

  • is there a question here? No one is sure what will happen when you try to create the RAID 10 array, because this is YOUR custom setup... – August Sep 16 '11 at 16:32
  • I guess my question is if it's possible to duplicate my server managing the RAID array while using the same iSCSI targets? Since the array is being built on raw devices I can't stick another layer in there like GFS. – J.R. Sep 16 '11 at 16:51
  • I think you are going to end up with latency and performance problems in this setup. You are using a NAS to create an iSCSI LUN - most prosumer level NASes (heck, even professional ones) don't have great iSCSI performance due to the way they have to implement a LUN in their filesystem, as well as their particular iSCSI implementation. Then you go via iSCSI over Ethernet to a central server, and then serve it out over NFS.... it just seems like a recipe for poor performance. Why not just get a SAS enclosure for this centralized server and put all your 1TB drives in it, then run that? – Jeremy Oct 2 '11 at 15:17
  • My goal was to add redundancy and performance to our setup without spending more money. I did several I/O tests along the way and there was no difference between NFS and iSCSI going directly to the NAS. I did see a performance boost when I added RAID-10. I also addressed my question here by using ucarp to share the same IP across the two servers. As soon as one goes down the other one takes over the RAID-10 and NFS export. It's not the prettiest setup but it's an improvement from before and we didn't have to purchase any new equipment or software. – J.R. Oct 2 '11 at 17:21
  • @JR - But did you test latency? – Jeremy Oct 4 '11 at 16:52

While this is an interesting approach, I believe you are correct in realizing that the software RAID-10 won't work when you try to extend it to another server. Instead, I think you'll need something like DRDB or GlusterFS to achieve your goals (or possibly both, and/or a clustering filesystem like OCFS2 or GFS).

| improve this answer | |

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.