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Some customers are afraid of thin provisioning…
Practically every week I have discussions with customers about leveraging thin provisioning to reduce their storage costs and just as often the customer pushes back worried that some day, some number of applications, for some reason, will suddenly consume all of their allocated space in a short period of time and cause the storage pool to run out of space. If this was to happen, every application using that storage pool will essentially experience an outage and resolving the problem requires allocating more space to the pool, migrating data, and/or deleting data, each of which would take precious time and/or money. In my opinion, this fear is the primary gating factor to customers using thin provisioning. Exacerbating the issue, most large organizations have a complex procurement process that forces them to buy storage many months in advance of needing it, further reducing the usefulness of thin provisioning. The IT organization for one of my customers can only purchase new storage AFTER a business unit requests it and approved by senior management; and they batch those requests before approving a storage purchase. This means that the business unit may have to wait months to get the storage they requested.
This same customer recently purchased a Symmetrix VMAX with FASTVP and will be leveraging sub-LUN tiering with SSD, FC, and SATA disks totaling over 600TB of usable capacity in this single system. As we began design work for the storage array the topic of thin provisioning came up and the same fear of running out of space in the pool was voiced. To prevent this, the customer fully allocates all LUNs in the pool up front which prevents oversubscription. It’s an effective way to guarantee performance and availability but it means that any free space not used by application owners is locked up by the application server and not available to other applications. If you take their entire environment into account with approximately 3PB of usable storage and NO thin provisioning, there is probably close to $1 million in storage not being used and not available for applications. If you weigh the risk of an outage causing the loss of several million dollars per hour of revenue, the customer has decided the risks outweigh the potential savings. I’ve seen this decision made time and again in various IT shops.
Sub-LUN Tiering pushes the costs for growth down
I previously blogged about using cloud storage for block storage in the form of Cirtas BlueJet and how it would not be to much of a stretch to add this functionality to sub-LUN tiering software like EMC’s FASTVP to leverage cloud storage as a block storage tier as shown in this diagram.
Let’s first assume the customer is already using FASTVP for automated sub-LUN tiering on a VMAX. FASTVP is already identifying the hot and cold data and moving it to the appropriate tier, and as a result the lowest tier is likely seeing the least amount of IOPS per GB. In a VMAX, each tier consists of one or more virtual provisioned pools, and as the amount of data stored on the array grows FASTVP will continually adjust, pushing the hot data up to higher tiers and cold data down to the lower tiers The cold data is more likely to be old data as well so in many cases the data sort of ages down the tiers over time and its the old/least used portion of the data that grows. Conceptually, the only tier you may have to expand is the lowest (ie: SATA) when you need more space. This reduces the long term cost of data growth which is great. But you still need to monitor the pools and expand them before they run out of space, or an outage may occur. Most storage arrays have alerts and other methods to let you know that you will soon run out of space.
Risk-Free Thin Provisioning
What if the storage array had the ability automatically expand itself into a cloud storage provider, such as AT&T Synaptic, to prevent itself from running out of space? Technically this is not much different from using the cloud as a tier all it’s own but I’m thinking about temporary use of a cloud provider versus long term. The cloud provider becomes a buffer for times when the procurement process takes too long, or unexpected growth of data in the pool occurs. With an automated tiering solution, this becomes relatively easy to do with fairly low impact on production performance. In fact, I’d argue that you MUST have automated tiering to do this or the array wouldn’t have any method for determining what data it should move to the cloud. Without that level of intelligence, you’d likely be moving hot data to the cloud which could heavily impact performance of the applications.
Once the customer is able to physically add storage to the pool to deal with the added data, the array would auto-adjust by bringing the data back from the cloud freeing up that space. The cloud provider would only charge for the transfer of data in/out and the temporary use of space. Storage reduction technologies like compression and de-duplication could be added to the cloud interface to improve performance for data stored in the cloud and reduce costs. Zero detect and reclaim technologies could also be leveraged to keep LUNs thin over time as well as prevent the movement of zero’d blocks to the cloud.
Using cloud storage as a buffer for thin provisioning in this way could reduce the risk of using thin provisioning, increasing the utilization rate of the storage, and reducing the overall cost to store data.
What do you think? Would you feel better about oversubscribing storage pools if you had a fully automated buffer, even if that buffer cost some amount of money in the event it was used?
I’ve been having some fun discussions with one of my customers recently about how to tackle various application problems within the storage environment and it got me thinking about the value of having “options”. This customer has an EMC Celerra Unified Storage Array that has Fiber Channel, iSCSI, NFS, and CIFS protocols enabled. This single storage system supports VMWare, SQL, Web, Business Intelligence, and many custom applications.
The discussion was specifically centered on ensuring adequate storage performance for several different applications, each with a different type of workload…
1.) Web Servers – Primarily VMs with general-purpose IO loads and low write ratios.
2.) SQL Servers – Physical and Virtual machines with 30-40% write ratios and low latency requirements.
3.) Custom Application – A custom application database with 100% random read profiles running across 50 servers.
The EMC Unified solution:
EMC Storage already sports virtual provisioning in order to provision LUNs from large pools of disk to improve overall performance and reduce complexity. In addition, QoS features in the array can be used to provide guaranteed levels of performance for specific datasets by specifying minimum and maximum bandwidth, response time, and IO requirements on a per-LUN basis. This can help alleviate disk contention when many LUNs share the same disks, as in a virtual pool. Enterprise Flash Drives (EFD) are also available for EMC Storage arrays to provide extremely high performance to applications that require it and they can coexist with FC and SATA drives in the same array. Read and write cache can also be tuned at an array and LUN level to help with specific workloads. With the updates to the EMC Unified Platform that I discussed previously, Sub-LUN FAST (auto tiering), and FAST Cache (EFD used as array cache) will be available to existing customers after a simple, non-disruptive, microcode upgrade, providing two new ways to tackle these issues.
So which feature should my customer use to address their 3 different applications?
Sub-LUN FAST (Fully Automated Storage Tiering)
Put all of the data into large Virtual Provisioning pools on the array, add a few EFD (SSD) and SATA disks to the mix and enable FAST to automatically move the blocks to the appropriate tier of storage. Over time the workload would even out across the various tiers and performance would increase for all of the workloads with much fewer drives, saving on power, floor space, cooling, and potentially disk cost depending on the configuration. This happens non-disruptively in the background. Seems like a no-brainer right?
For this customer, FAST helps the web server VMs and the general-purpose SQL databases where the workload is predominately read and much of the same data is being accessed repeatedly (high locality of reference). As long as the blocks being accessed most often are generally the same, day-to-day, automated tiering (FAST) is a great solution. But what if the workload is much more random? FAST would want to push all of the data into EFD, which generally wouldn’t be possible due to capacity requirements. Okay, so tiering won’t solve all of their problems. What about FAST Cache?
Exponentially increase the size of the storage array’s read AND write cache with EFD (SSD) disks. This would improve performance across the entire array for all “cache friendly” applications.
For this customer, increasing the size of write cache definitely helps performance for SQL (50% increase in TPM, 50% better response time as an example) but what about their custom database that is 100% random read? Increasing the size of read cache will help get more data into cache and reduce the need to go to disk for reads, but the more random the data, the less useful cache is. Okay, so very large caches won’t solve all of their problems. EFDs must be the answer right?
Forget SATA and FC disks; just use EFD for everything and it will be super fast!! EFD has extremely high random read/write performance, low latency at high loads, and very high bandwidth. You will even save money on power and cooling.
The total amount of data this customer is dealing with in these three applications alone exceeds 20TB. To store that much in EFD would be cost prohibitive to say the least. So, while EFD can solve all of this customer’s technical problems, they couldn’t afford to acquire enough EFD for the capacity requirements.
But wait, it’s not OR, it’s AND
The beauty of the EMC Unified solution is that you can use all of these technologies, together, on the same array, simultaneously.
In this customer’s case, we put FC and SATA into a virtual pool with FAST enabled and provision the web and general-purpose SQL servers from it. FAST will eventually migrate the least used blocks to SATA, freeing the FC disks for the more demanding blocks.
Next, we extend the array cache using a couple EFDs and FAST Cache to help with random read, sequential pre-fetching, and bursty writes across the whole array.
Finally, for the custom 100% random read database, we dedicate a few EFDs to just that application, snapshot the DB and present copies to each server. We disable read and write cache for the EFD backed volumes which leaves more cache available to the rest of the applications on the array, further improving total system performance.
Now, if and when the customer starts to see disk contention in the virtual pool that might affect performance of the general-purpose SQL databases, QoS can be tuned to ensure low response times on just the SQL volumes ensuring consistent performance. If the disks become saturated to the point where QoS cannot maintain the response time or the other LUNs are suffering from load generated by SQL, any of the volumes can be migrated (non-disruptively) to a different virtual pool in the array to reduce disk contention.
If you look at offerings from the various storage vendors, many promote large virtual pools, some also promote large caches of some kind, others promote block level tiering, and a few promote EFD (aka SSDs) to solve performance problems. But, when you are consolidating multiple workloads into a single platform, you will discover that there are weaknesses in every one of those features and you are going to wish you had the option to use most or all of those features together.
You have that option on EMC Unified.
This past week, during EMC World 2010 in Boston, EMC made several announcements of updates to the Celerra and CLARiiON midrange platforms. Some of the most impressive were new capabilities coming to CLARiiON FLARE in just a couple short months. Major updates to Celerra DART will coincide with the FLARE updates and if you are already running CLARiiON CX4 hardware, or are evaluating CX4 (or Celerra), you will want to check these new features out. They will be available to existing CX4(120,240,480,960)/NS(120,480,960) systems as part of a software update.
Here’s a list of key changes in FLARE 30:
- Unified management for midrange storage platforms including CLARiiON and Celerra today, plus RecoverPoint, Replication Manager and more in the future. This is a true single pane of glass for monitoring AND managing SAN, NAS, and data protection and it’s built in to the platform. ”EMC Unisphere” replaces Navisphere Manager and Celerra Manager and supports multiple storage systems simultaneously in a single window. (Video Demo)
- Extremely large cache (ie: FASTCache) – Up to 2TB of additional read/write cache in CLARiiON using SSDs (Video Demo)
- Block level Fully Automated Storage Tiering (ie: sub-LUN FAST) – Fully automated assignment of data across multiple disk types
- Block Level Compression – Compress LUNs in the CLARiiON to reduce disk space requirements
- VAAI Support – Integrate with vSphere ESX for improved performance
These features are in addition to existing features like:
- Seamless and non-disruptive mobility of LUNs within a storage array – (via Virtual LUNs)
- Non-Disruptive Data Migration – (via PowerPath Migration Enabler)
- VMWare Aware Storage Management – (Navisphere, Unisphere, and vSphere Plugins giving complete visibility and self-service provisioning for VMWare admins (Video Demo) AND Storage Admins
- CIFS and NFS Compression – Compress production data on Celerra to reduce disk space requirements including VMs
- Dynamic SAN path load balancing – (via PowerPath)
- At-Rest-Encryption – (via PowerPath w/RSA)
- SSD, FC, and SATA drives in the same system – Balance performance and capacity as needed for your application
- Local and Remote replication with array level consistency – (SnapView, MirrorView, etc)
- Hot-swap, Hot-Add, Hot-Upgrade IO Modules – Upgrade connectivity for FC, FCoE, and iSCSI with no downtime
- Scale to 1.8PB of storage in a single system
- Simultaneously provide FC, iSCSI, MPFS, NFS, and CIFS access
All together, this is an impressive list of features for a single platform. In fact, while many of EMC’s competitors have similar features, none of them have all of them in the same platform, or leverage them all simultaneously to gain efficiency. When CLARiiON CX4 and Celerra NS are integrated and managed as a single Unified storage system with EMC Unisphere there is tremendous value as I’ll point out below…
Improve Performance easily…
- Install a couple SSD drives into a CLARiiON and enable FASTCache to increase the array’s read/write cache from the industry competive 4GB-32GB up to 2TB of array based non-volatile Read AND Write cache available to ALL applications including NAS data hosted by the array.
- Install PowerPath on Windows, Linux, Solaris, AND VMWare ESX hosts to automatically balance IO across all available paths to storage. PowerPath detects latency and queuing occuring on each path and adjusts automatically, improving performance at the storage array AND for your hosts. This is a huge benefit in VMWare environments especially.
- When VMWare releases the updated version of vSphere ESX that supports VAAI, ESX will be able to leverage VAAI support in the CLARiiON to reduce the amount of IO required to do many tasks, improving performance across the environment again.
- Upgrade from 1gbe iSCSI to 10gbe iSCSI, or from 4gbe FiberChannel to 8gbe FiberChannel, without a screwdriver or downtime.
- Provide NAS shared file access with block-level performance for any application using EMC’s MPFS protocol.
Improve Efficiency and cost easily…
- Create a single pool of storage containing some SSD, some FC, and some SATA drives, that automatically monitors and moves portions of data to the appropriate disk type to both improve performance AND decrease cost simultaneously.
- Non-disruptively compress volumes and/or files with a single click to save 50% of your disk space in many cases.
- Convert traditional LUNs to more efficient Thin-LUNs non-disruptively using PowerPath Migration Enabler, saving more disk space.
Increase and Manage Capacity easily…
- Add additional storage non-disruptively with SSD, FC, and SATA drives in any mix up to 1.8PB of raw storage in a single CLARiiON CX4.
- Using FASTCache, iSCSI, FC, and FCoE connectivity simultaneously does not reduce total capacity of the system.
- Expanding LUNs, RAID Groups, and Storage Pools is non-disruptive.
- Migrating LUNs between RAID groups and/or Storage Pools is non-disruptive using built-in CLARiiON LUN Migration, as is migrating data to a different storage array (using PowerPath Migration Enabler)!
- Balancing workload between storage processors is non-disruptive and at individual LUN granularity.
Protect your data easily…
- Snapshot, Clone, and Replicate any of the data to anywhere with built in array tools that can maintain complete data consistency across a single, or multiple applications without installing software.
- Maintain application consistency for Exchange, SQL, Oracle, SAP, and much more, even within VMWare VMs, while replicating to anywhere with a single pane-of-glass.
- Encrypt sensitive data seamlessly using PowerPath Encryption w/RSA.
- While you can do all of these things quickly and simply, you still have the flexibility to create traditional RAID sets using RAID 0, 1, 5, 6, and 10 where you need highly predicable performance, or tune read and write cache at the array and LUN level for specific workloads. Do you want read/write snapshots? How about full copy clones on completely separate disks for workload isolation and failure protection? What about the ability to rollback data to different points in time using snapshots without deleting any other snapshots? EMC Storage arrays have been able to do this for a long time and that hasn’t changed.
There are few manufacturers aside from EMC that can provide all of these capabilities, let alone provide them within a single platform. That’s the definition of simple, efficient, Unified Storage in my opinion.