Questions[dell-equallogic](server)

Recently I have consolidated all our Dell Equallogic SANs into the same group; previously each SAN was in its own group. They are all populated with 15k RPM SAS drives in RAID 6 so I haven't bothered to tier the storage of the new consolidated group as they're basically all the same.

In the process of doing so, I have changed all our VMs to use VMDK storage instead of iSCSI because I believe the performance to be better.

I'm being told now that the disk I/O performance of our MS SQL 2005 server (our main SQL box, for now) has been consistently worse than prior to performing these operations, but I can't see how that could be... its disks (C - OS, D - MDFs, E - LDFs) are now spanned across way more read heads than they were previously, and my understanding is that VMDK storage is more performant than iSCSI.

So what gives? Here's a graph of the "total I/O wait time" from Solarwinds Database Performance Analyzer:

I have a long-term goal of setting up a DR site in a colo somewhere and part of that plan includes replicating some volumes of my EqualLogic SAN. I'm having a bit of a difficult time doing this because I don't know if my method is sound.

This post may be a bit lengthy for the sake of completeness.

Generally relevant information:

1. I have one EqualLogic PS4000X (~4TB).
2. The SAN Acts as shared storage for 2 ESXi hosts in vSphere 5 environment.
3. I have 4 volumes of 500GB each. Volumes 1 and 2 contain my "tier 1" VMs. These will be the only volumes I plan to replicate.
4. Currently have 3Mb/s connection with actual data bandwidth at ~2.8Mb/s because of our PRI(voice).

My method of measuring change in a volume:

I was told by a Dell rep that a way (perhaps not the best?) to estimate deltas in a volume is to measure the snapshot reserve space used over a period of time of a regular snapshot schedule.

My first experiment with this was to create a schedule of 15 minutes between snapshots with a snapshot reserve of 500GB. I let this run overnight and until COB the following day. I don't recall the number of snapshots that could be held in 500GB but I ended up with an average of ~15GB per snapshot.

$average_snapshot_delta = $snapshot_reserve_used / $number_of_snapshots

I then changed the snapshot interval to 60 minutes which after a full 24 hours passing means a total of 13 snapshots in 500GB. This leaves me with ~37GB per hour (or ~9GB per 15 mins).

The problem:

These numbers are astronomical to me. With my bandwidth I can do a little over 1GB/hour with 100% utilization. Is block-level replication this expensive or am I doing something completely wrong?

We are thinking about purchasing 4 x EqualLogic PS6510X SANs (the Sumo boxes). Each has 48 x 600GB 10k SAS drives.

They will be stacked to form a logical pool of storage (all in the same location).

I understand that when you create a RAID group its done on a "per box" basis. So one box could be Raid 50, another Raid 10 etc.

My question is, should I make one box a "performance" box ie Raid 10, and the other boxes "standard" ie Raid50? How do people configure their EQL arrays in the real world?

We have several Dell 6248 swtich stacks (of 3 each) that form the backbone of our iSCSI Storage network. We need to perform firmware updates on the switch stacks, but are concerned about the downtime required.

By way of information our storage is exclusively Dell/Equallogic PS6000 series enclosures with 3 or 4 GigE uplinks per enclosure.

As you might already know, these switches can't be upgraded a member at a time, and the reboot required to upgrade the switches is on the order of two minutes (i.e. longer than the iSCSI initiator timeout for a volume).

Does anyone have any suggestions for how we might be able to accomplish a iSCSI SAN switch stack upgrade while minimizing downtime?

Thanks for any help or suggestions.

Joe

Its standard practice to separate log and data files to separate disks away from the OS (tempdb, backups and swap file also) Does this logic still make sense when your drives are all SAN based and your LUNS are not carved of specific disk or raid sets -they are just part of the x number of drives on the SAN and the LUN is just space allocation