Scalix Forums

Everyone:

We are still in the process of evaluating Scalix and are very excited about it -- thanks to the Scalix team for answering our questions so far. We are preparing ot buy a new server and storage to host the Scalix installation.

We will be supporting 200-600 users (we haven't yet decided if we will migrate students to this box) and are wondering whether iSCSI will be fast enough for our storage needs. We are considering a Snap 4500 or similar. The alternative would be DAS or Fibre Channel. At this point, we believe that approximately 1/3 of the users will be using SWA, 1/3 will use Outlook, and another 1/3 will use an IMAP client like OE or Thunderbird.

Any guidance anyone could give would be appreciated. Is anyone using iSCSI for storage successfully?

Thanks,

Ben Chapman

At Scalix, we haven't tested iSCSI in our performance tests so we would recommend DAS or FibreChannel.

At present, we have no plans to test with iSCSI but this could change in the future depending upon customer demand.

As a side note, iSCSI was introduced into the 2.6 kernel in June this year (2.6.12) and it looks like RHEL4 update 2 contains the implementation from linux-iscsi.sourceforge.net. I know that it's been used with vendor-supplied drivers in the past but the implementation is still pretty new. Is there a reason why you are looking at iSCSI ? I'm asking more out of curiosity than anything else.

Cheers

Dave

Hmmmm... I thought the iSCSI support was more mature than that. The (Cisco-written?) notes at linux-iscsi.sf.net suggest that iSCSI works with a 2.4 or newer kernel series. Regardless, I'm not keen to install a configuration that you all do not support.

The reason for looking at iSCSI comes down to budget, plus it seems easier to support than FC.

Thanks,

Ben

I wouldn't say iSCSI is easier to support (but it is cheaper. :) ). FC is relatively easy as its just a SCSI block device on a cable once you load your HBA module. iSCSI will involve patching your kernel unless you have a distro with iSCSI support. (SLES 9, RHEL3) The iSCSI in the kernel is only the generic iSCSI transport and isnt an iSCSI implementation , rather a generic interface. The open-iscsi group (which is now linux-iscsi merged with the open-iscsi group) would like to see their work merged soon. (I believe it was in Andrew Mortons 2.6.13-mm but didnt make the merge) The older iscsi, linux-iscsi (the Cisco based) are stable and work well, but only patches against 2.6.10 kernel or <. The newer open-iscsi drivers are faster and implement less in kernel space but may have stability/compatibility issues since they don't have a stable release yet. In some of testing I did, my iSCSI over gigE performed as well or better than local IDE disk, except when copying or moving data from a lun to another place on the same lun. So backups need to go to their own lun on the SAN, otherwise the you may find the iscsid is blocking writes from the Scalix server while waiting on I/O. I only have 100 users on my server so your milage may vary, :)

-Josh