Life made easy – Dell EqualLogic storage swap
When it comes to storage, the EqualLogic PS-series amazes me every time.
Last Tuesday I was at a client site investigating performance issues but when I opened SANHQ and the web interface on the PS 6000E one thing stood out. The performance issues were not caused by the storage device. The PS 6000E is hosting 12 virtualized Citrix XenApp servers en 8 supporting VMs and during heavy load the average latency is 1,2ms with a read/write ratio of 28%/72% and a max of 1100 IOPS.
But yesterday we had to swap SANs, a PS 5000XV for a PS 6000E and the ease with which this can be done amazes me every time. The hardest part was the process of endless firmware updates on the PS 5000XV to get it to a respectable level to get it to join the PS 6000 in the same storage group.
We had to upgrade from firmware version 3.3.0 to 4.3.4 but this is no simple task because you cannot directly apply 4.3.4. First we had to upgrade to 4.0.7, then to 4.1.7, to 4.3.4. Every time uploading the firmware using FTP, updating both controllers, restarting. This took us almost 2 hours to complete.
When this was done, all that was left was to join the PS 6000 in the existing storage group and evict the PS 5000 and this is the process that amazes me every time.
The ease with which this is done and the availability during this process. Just configure the new PS 6000 with the Remote Setup wizard which comes with the Host Integration Toolkit and join an existing group, configure the desired RAID level and join the storage pool. Now the two SANs level out the available volumes in the storage pool and spread them out over all disks.
When this was done we could evict the PS 5000XV from the storage pool and Storage group. By doing this all volumes are completely moved to the remaining SAN (PS 6000) and when completed the PS 5000 is removed from the storage group.
During this process the volumes were available the whole time and besides the password recovery and firmware upgrades we could have performed this during office hours.
The only downside to this whole process is the speed of the replication/move of the volumes to their new location. We measured a whopping speed of 2 GB/minute, so the total process took approximately 12 hours for a 1,5 TB volume. During this process only 1 nic on the PS series SAN is used to transfer the data. So although you have three 1 Gb/s links and a theoretical transfer speed of 22,5 GB/minute you only get 10%. True, this leaves 90% for normal every day use so you can do this during business hours but it would have been nice if we had the possibility to adjust this ‘setting’.
Nevertheless, because of the ease of use of the Dell EqualLogic PS series, I became a great iSCSI fan and it still amazes me every time.