Dell Equallogic limitations
If you have been reading my blog, you will have noticed that I am a fan of Equallogic SAN's and have been using them successfully for several months now. However, there are some things that you must know before you make your purchase to decide if it is the right storage environment for your needs. These are talking points that the competition to Equallogic should be focused on but Equallogic does a good job of hiding its weaknesses.
The concept of a Equallogic chassis is that it is virtualized storage, meaning that the entire chassis must contain one and only one storage pool. If you have been involved with an EMC SAN before, the concept of RAID Groups will not work here. For example, if you buy a 48 drive Equallogic SAN, then that entire chassis must be dedicated to a single RAID policy. There is no concept of dedicating certain disks to a certain volume or make certain disks in the chassis RAID 10 vs RAID 5. Equallogic wants you to buy another chassis to use with high performance applications or a dedicated application which can obviously get expensive.
I found this out the hard way over the last couple of weeks when I was trouble-shooting performance issues with a linux application. I wanted to create a RAID group like I can with an EMC array but was unable to and then was told to just buy another chassis to dedicate spindles to a particular application. I even tried to install and configure some QLogic iSCSI host bus adapters and they actually produced worst results than standard multi-pathing of NIC's on this linux server.
Equallogic is really good at bulk storage and simplicity of administration, but if you are interested in doing more with your SAN then it may be best to look elsewhere. Otherwise, you will need to buy several chassis's in order for it to work like an EMC array.
posted by Rick Mitchell Solutions @ 4:38 PM
2 Comments:
At May 19, 2010 10:34 AM ,
michaelellerbeck.com said...
EqualLogic is very simple and you can allow it to manage a lot of things for you! It is annoying though when you run across something that you could do with a different solution that you can't do with it! Defining RAID across the member is an interesting decision. I think it is aimed at simplicity as well as not stranding performance. It is an two sided coin though, you are able to very simply add another member (very nice ease of use) but then again you have to buy another one :) when you do add another member you would get the performance advantages (if you spread your volume across) of all the added spindles and controllers. But I do see where you are coming from, there is a lot of documentation to read through, and finding relevant bits is challenging. If you ask they do tell you about one RAID level per member so it's not like they are shy about it, I think they are in fact proud of it. Another one that hit me was the 512 iscsi connection limit. Another one that could hit you is the 16MB pages that are used for snapshots. EQL snapshots are kindof piggy. But, taking this all together I still love this SAN. It's not perfect, but nothing is. For its price, performance and usability it works great!
At May 19, 2010 1:01 PM ,
Rick Mitchell Solutions said...
I agree it works great, but there are times where people don't see the limitations in the technology. I just wanted to point those out for folks before they make their investment. Thanks for writing!
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