One platform to rule them all – Compellent&EqualLogic&Exanet from Dell

Compellent drive enclosure (c) 2010 Compellent (from
Compellent drive enclosure (c) 2010 Compellent (from

Dell and Compellent may be a great match because Compellent uses commodity hardware combined with specialized software to create their storage subsystem. If there’s any company out there that can take advantage of commodity hardware it’s probably Dell. (Of course Commodity hardware always loses in the end, but that’s another story).

Similarly, Dell’s EqualLogic iSCSI storage system uses commodity hardware to provide its iSCSI storage services.  It doesn’t take a big leap of imagination to have one storage system that combines the functionality of EqualLogic’s iSCSI and Compellent’s FC storage capabilities.  Of course there are others already doing this including Compellent themselves which have their own iSCSI support already built into their FC storage system.

Which way to integrate?

Does EqualLogic survive such a merger?  I think so.  It’s easy to imagine that Equal Logic may have the bigger market share today. If that’s so, the right thing might be  to merge Compellent FC functionality into EqualLogic.  If Compellent has the larger market, the correct approach is the opposite. The answer lies probably with a little of both.  It seems easiest to add iSCSI functionality to a FC storage system than the converse but the FC to iSCSI approach may be the optimum path for Dell, because of the popularity of their EqualLogic storage.

What about NAS?

The only thing missing from this storage system is NAS.  Of course the Compellent storage offers a NAS option through the use of a separate Windows Storage Server (WSS) front end.  Dell’s EqualLogic does the much the same to offer NAS protocols for their iSCSI system.  Neither of these are bad solutions but they are not a fully integrated NAS offering such as available from NetApp and others.

However, there is a little discussed part, the Dell-Exanet acquisition which happened earlier this year. Perhaps the right approach is to integrate Exanet with Compellent first and target this at the high end enterprise/HPC market place, keeping Equal Logic at the SMB end of the marketplace.  It’s been a while since I have heard about Exanet, and nothing since the acquisition earlier this year.  Does it make sense to backend a clustered NAS solution with FC storage – probably.


Much of this seems doable to me, but it all depends on taking the right moves once the purchase is closed.   But if I look at where Dell is weakest (baring their OEM agreement with EMC), it’s in the highend storage space.  Compellent probably didn’t have much of a foot print there as possible due to their limited distribution and support channel.  A Dell acquisition could easily eliminate these problems and open up this space without having to do much other than start to marketing, selling and supporting Compellent.

In the end, a storage solution supporting clustered NAS, FC, and iSCSI that combined functionality equivalent to Exanet, Compellent and EqualLogic based on commodity hardware (ouch!) could make a formidable competitor to what’s out there today if done properly. Whether Dell could actually pull this off and in a timely manner even if they purchase Compellent, is another question.


ESRP 1K to 5Kmbox performance – chart of the month

ESRP 1001 to 5000 mailboxes, database transfers/second/spindle
ESRP 1001 to 5000 mailboxes, database transfers/second/spindle

One astute reader of our performance reports pointed out that some ESRP results could be skewed by the number of drives that are used during a run.  So, we included a database transfers per spindle chart in our latest Exchange Solution Review Program (ESRP) report on 1001 to 5000 mailboxes in our latest newsletter.  The chart shown here is reproduced from that report and shows the number of overall database transfers attained (total of read and write) for the top 10 storage subsystems reporting in the latest ESRP results.

This cut of the system performance shows a number of diverse systems:

  • Some storage systems had 20 disk drives and others had 4.
  • Some of these systems were FC storage (2), some were SAS attached storage (3), but most were iSCSI storage.
  • Mailbox counts supported by these subsystems ranged from 1400 to 5000 mailboxes.

What’s not shown is the speed of the disk spindles. Also none of these systems are using SSD or NAND cards to help sustain their respective workloads.

A couple of surprises here:

  • iSCSI systems should have shown up much worse than FC storage. True, the number 1 system (NetApp FAS2040) is FC while the numbers 2&3 are iSCSI, the differences are not that great.  It would seem that protocol overhead is not a large determinant in spindle performance for ESRP workloads.
  • The number of drives used also doesn’t seem to matter much.  The FAS2040 had 12 spindles while the AX4-5i only had 4.  Although this cut of the data should minimize drive count variability, one would think that more drives would result in higher overall performance for all drives.
  • Such performance approaches drive limits of just what a 15Krpm drive can sustain.  No doubt some of this is helped by system caching, but no amount of cache can hold all the database write and read data for the duration of a Jetstress run.  It’s still pretty impressive, considering typical 15Krpm drives (e.g., Seagate 15K.6) can probably do ~172 random 64Kbyte block IOs/second. The NetApp FAS2040 hit almost 182 database transfers/second/spindle, perhaps not 64Kbyte blocks and maybe not completely random, but impressive nonetheless.

The other nice thing about this metric, is that it doesn’t correlate that well with any other ESRP metrics we track, such as aggregate database transfers, database latencies, database backup throughput etc. So it seems to measure a completely different dimension of Exchange performance.

The full ESRP report went out to our newsletter subscribers last month and a copy of the report will be up on the dispatches page of our website later this month. However, you can get this information now and subscribe to future newsletters to receive future full reports even earlier, just subscribe by email.

As always, we welcome any suggestions on how to improve our analysis of ESRP or any of our other storage system performance results.  This new chart was a result of one such suggestion.

SSD shipments start to take off

3 rack V-Max storage subsystem from EMC
3 rack V-Max storage subsystem from EMC

Was on an analyst call today where Bob Wambach of EMC was discussing their recent success with V-Max their newest version of their highly successful Symmetrix storage subsystem. But what was more interesting was their announcement of having sold 1PB of enterprise flash storage on Symmetrix and almost 2PB total across all EMC product lines in 1H09. Symmetrix SSD shipments includes both DMX and V-Max installs. During 1H09, EMC shipped both 146GB and 400GB SSDs, so it’s hard to put a number of drives on this capacity but at 146GBs 1PB of Symmetrix SSD this would be around 6.9K SSDs and for all SSDs a maximum of ~14K drives.

SSD drive shipments vs. hard drives

To put this in comparison, ~540M hard drive were shipped in 2008 and with a ~7% decline in 2009 this should equate to around 502M drive shipments in 2009. But this includes all drives and as such, if 15-20% of these were data center storage, then ~75 to ~100M data center hard drives will be shipped in ’09. Looking at just the first half, probably close to 40% of the whole year, then ~30-40M data center hard drives were shipped across the industry in 1H09. In Q2’09 EMC had a 22.4% revenue storage market share, using this market share for all of 1H09, this means they probably shipped ~7.8M data center hard drives during 1H09 (assuming revenue correlates with drive shipments). Hence, 14K SSDs represents a very small but growing proportion (<0.2%) of all drives sold by EMC.

Of course this is just the start

On the analyst call today EMC provided a couple of examples of recent SSD installations. In one example a customer was looking at a US$3M mainframe upgrade but instead went with a $500K SSD upgrade. EMC was able to examine their current storage, identify their hottest, most active LUNs and convert these to SSDs. Once this was done, EMC was able to solve the customers performance problems which allowed them to defer the mainframe upgrade.

Data center access patterns

Some statistics from an EMC year long, data center study analyzing detail IO traces from around 600 data centers, show that over 60% of data center data is infrequently accessed. EMC believes such data can best be left on high capacity SATA drives. As for the rest, it wouldn’t surprise me if 15-20% is accessed frequently enough to reside on SSD/flash drives for improved performance and the remaining 25-20% probably best be served today left on FC drives.

Nowadays, EMC goes through a manual analysis to identify which data to place on SSDs but in the near future their FAST (Fully Automated Storage Tiering) software will be able to migrate data to the right performing storage tier automatically. With FAST in place, supposedly one only needs to upgrade to SSDs and turn FAST on, after that it will analyze your data reference patterns and automatically move your performance critical data to SSDs.

The coming SSD world

So, SSDs are starting to be adopted, by organizations both large and small. Perhaps current SSD drive shipments are insignificant compared to hard drives, but given today’s realities of data use there seems no reason that SSD adoption can’t accelerate and someday claim 10% or more of all data center drive shipments. Hence, at todays numbers, this means almost 10 million SSDs being shipped each year.