Archive for Storage

Another IET recipe

Steffen shared another IET recipe with some nice features:

  • active/passive storage controller
  • configuration management across cluster
  • dynamic updating of running ietd environment
  • dynamically add new targets and LUNs
  • handle size changes of LUNs
  • logical volume backup

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A nice writeup on DRBD list about how to setup a HA configuration for Xen.

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Virtual ROM support

Recently I added a virtual ROM support to IET, details can be found here. One simple use is to export various OS installation ISO to ESX or Xen, so you can install OS easier.

Next step is to allow ISO files dynamic “ejected” and “loaded”, and a virtual DVD writer support. The code is done, just need to be polished. A fun but illegal use of this code is to clone a DVD .. to system as a ISO file, then you can watch it later at any time. Of course, when you have XVID and VIDX, you don’t need that right? 😉

Seriously, this can be used as WORM archiving purpose. Or do a disk staging for D2D2H.

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Another happy IET user

See how much people can save with OSS like IET.

” No more W2K-based “LanShare” servers for 50K Euros that crash every 2nd day. Just a Webinterface and a choice of emulated parallel SCSI (on FreeBSD) or iSCSI (Linux/IET).

The typical replacement for a REALLY crappy 50K Euro Lanshare has a hardware fingerprint of some 5K (using really good Hardware) … and you don’t need windows 😉 ”

So what you are waiting for? 😉

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D2D2T = Disk to Disk to Tape;

D2D2H = Disk to Disk to Holographic Storage.

InPhase finally commercialized the holographic storage. From the news floating in Web, we know first product has 300GB per media, around 27MB/s write speed. The media is about $180 each and the drive is over $10K.

So this is why I think we need D2D2H:

  • You need about 3 hours ((300GB / 27MB/s)) to write a full medium, this speed is too slow for nearline storage. So you need a disk-based staging area as a faster persistent cache;
  • Normal backup/archive does not need 300GB capacity thus you need many day’s backup in order to fill one medium. You do not want to take the medium in and out of the drive everyday right? So you still need a disk-based staging area to pile up these data;
  • You can not write to multiple media via _one_ drive at same time. And you do want to share this expensive drive among multiple peers. So you need a disk-based staging area to support multiple streams.
  • What else?…

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Oracle RAC + IET

Quite a few people want to use IET with Oracle, here is the information regarding disk caching and reservation from Ozgur from Oracle.


The SCSI2 and SCSI3 reservation features are not required by Oracle RAC with Oracle clusterware. SCSI3 PR is a requirement of “Veritas” clusterware. So any iSCSI implementation without PR would be ok with Oracle RAC and clusterware. RAC/PCW needs the following:

1. No buffering anywhere in the chain between the Oracle write and the disk subsystem This is provided via raw devices, OCFS or ASM.
2. Persistent naming of devices (by any means): The devices are needed to be named consistently for use of the Oracle clusterware (PCW).


So as long as you use default write-through mode in IET, disable all write cache in disk drive with hdparm, and use ScsiId or ScsiSN parameter for your LU, you are ready to go!

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Will from Premier IT reported on IET mailing list that they will open source a SAN deploy kit on Sourceforge.

“CHRIS tools allow you to create a Commodity Hardware Replicated iSCSI SAN with great ease. All you require are two servers onto which you can install RHEL4 or CentOS4 which have either an ips or 3w9xx based raid controller and have network interfaces and you can create a replicated SAN using DRBD + heartbeat by simply following a very user friendly wizard”.
I will keep my eyes on it and report the updates. It is nice to see more and more solutions around IET.

Thanks, Will!

Update: PCPro also has an article about DRBD+IET.

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