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Continuing my ongoing discussion on Solid State Disk (SSD), fellow blogger BarryB (EMC) points out in his [latest post]:
Oh – and for the record TonyP, I don't think I ever said EMC was using a newer or different EFDs than IBM. I just asserted that EMC knows more than IBM about these EFDs and how they actually work a storage array under real-world workloads.
(Here "EFD" is refers to "Enterprise Flash Drive", EMC's marketing term for Single Layer Cell (SLC) NAND Flash non-volatile solid-state storage devices. Both IBM and EMC have been selling solid-state storage for quite some time now, but EMC felt that a new term was required to distinguish the SLC NAND Flash devices sold in their disk systems from solid-state devices sold in laptops or blade servers. The rest of the industry, including IBM, continues to use the term SSD to refer to these same SLC NAND Flash devices that EMC is referring to.)
The disagreement resulted from his earlier statement from his post[IBM's amazing...part deux]:
Although STEC asserts that IBM is using the latest ZeusIOPS drives, IBM is only offering the 73GB and 146GB STEC drives (EMC is shipping the latest ZeusIOPS drives in 200GB and 400GB capacities for DMX4 and V-Max, affording customers a lower $/GB, higher density and lower power/footprint per usable GB.)
Here is where I enjoy the subtleties between marketing and engineering. Does the above seem like he is saying EMC is using newer or different drives? What are typical readers expected to infer from the statement above?
Uncontested, some readers might infer the above and come to the wrong conclusions. I made an effort to set the record straight. I'll summarize with a simple table:
So, we all agree now that the 256GB drives that are formatted as 146GB or 200GB are in fact the same drives, that IBM and EMC both sell the latest drives offered by STEC, and that the STEC press release was in fact correct in its claims.
I also wanted to emphasize that IBM chose the more conservative format on purpose. BarryB [did the math himself] and proved my key points:
I agree with BarryB that an aggressive format can offer a lower $/GB than the conservative format. Cost-conscious consumers often look for less-expensive alternatives, and are often willing to accept less-reliable or shorter life expectancy as a trade-off. However, "cost-conscious" is not the typical EMC targeted customer, who often pay a premiumfor the EMC label. To compensate, EMC offers RAID-6 and RAID-10 configurations to provide added protection. With a conservative format, RAID-5 provides sufficient protection.
(Just so BarryB won't accuse me of not doing my own math, a 7+P RAID-5 using conservative format 146GB drives would provide 1022GB of capacity, versus 4+4 RAID-10 configuration using aggressive format 200GB drives only 800GB total.)
In an ideal world, you the consumer would know exactly how many IOPS your application will generate over the next five years, exactly how much capacity you will require, be offered all three drives in either format to choose from, and make a smart business decision. Nothing, however, is ever this simple in IT.Read More]
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My post last week [Solid State Disk on DS8000 Disk Systems] kicked up some dust in the comment section.Fellow blogger BarryB (a member of the elite [Anti-Social Media gang from EMC]) tried to imply that 200GB solid state disk (SSD) drives were different or better than the 146GB drives used in IBM System Storage DS8000 disk systems. I pointed out that they are the actual same physical drive, just formatted differently.
To explain the difference, I will first have to go back to regular spinning Hard Disk Drives (HDD). There are variances in manufacturing, so how do you make sure that a spinning disk has AT LEAST the amount of space you are selling it as? The solution is to include extra. This is the same way that rice, flour, and a variety of other commodities are sold. Legally, if it says you are buying a pound or kilo of flour, then it must be AT LEAST that much to be legal labeling. Including some extra is a safe way to comply with the law. In the case of disk capacity, having some spare capacity and the means to use it follows the same general concept.
(Disk capacity is measured in multiples of 1000, in this case a Gigabyte (GB) = 1,000,000,000 bytes, not to be confused with [Gibibyte (GiB)] = 1,073,741,824 bytes, based on multiples of 1024.)
Let's say a manufacturer plans to sell 146GB HDD. We know that in some cases there might be bad sectors on the disk that won't accept written data on day 1, and there are other marginally-bad sectors that might fail to accept written data a few years later, after wear and tear. A manufacturer might design a 156GB drive with 10GB of spare capacity and format this with a defective-sector table that redirects reads/writes of known bad sectors to good ones. When a bad sector is discovered, it is added to the table, and a new sector is assigned out of the spare capacity.Over time, the amount of space that a drive can store diminishes year after year, and once it drops below its rated capacity, it fails to meet its legal requirements. Based on averages of manufacturing runs and material variances, these could then be sold as 146GB drives, with a life expectancy of 3-5 years.
With Solid State Disk, the technology requires a lot of tricks and techniques to stay above the rated capacity. For example, you can format a 256GB drive as a conservative 146GB usable, with an additional 110GB (75 percent) spare capacity to handle all of the wear-leveling. You could lose up to 22GB of cells per year, and still have the rated capacity for the full five-year life expectancy.
Alternatively, you could take a more aggressive format, say 200GB usable, with only 56GB (28 percent) of spare capacity. If you lost 22GB of cells per year, then sometime during the third year, hopefully under warranty, your vendor could replace the drive with a fresh new one, and it should last the rest of the five year time frame. The failed drive, having 190GB or so usable capacity, could then be re-issued legally as a refurbished 146GB drive to someone else.
The wear and tear on SSD happens mostly during erase-write cycles, so for read-intensive workloads, such as boot disks for operating system images, the aggressive 200GB format might be fine, and might last the full five years.For traditional business applications (70 percent read, 30 percent write) or more write-intensive workloads, IBM feels the more conservative 146GB format is a safer bet.
This should be of no surprise to anyone. When it comes to the safety, security and integrity of our client's data, IBM has always emphasized the conservative approach.[Read More]
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Well, it's Tuesday, which means IBM makes its announcements!
This week, IBM announces that it now supports 50GB Solid State Disk (SSD) in its [IBM System Storage EXP3000] disk systems.IBM has already made announcements about SSD enablement in the DS8000 and SAN Volume Controller (SVC), but now the EXP3000 brings SSD technology down to smaller System x server deployments.
Adoption of this new exciting technology is still in the early stages, despite the fact that IBM and other vendors have been touting this technology for a while. (For a quick blast to the past, here was my first post on the subject back from December 20, 2006: [Hybrid, Solid State and the future of RAID])Recently, fellow blogger BarryB admitted that EMC have only sold SSD to [hundreds of their customers], and to be fair, I suspect IBM's sales of SSD in its BladeCenter servers [available since July 2007] have been in similar single-digit percentage territory as well.
The advantage of today's announcement is that you can mix and match SSD drives with SAS and SATA drives in the EXP3000. You won't have to buy the entire drawer of SSD, you can start with just a few, depending on your business needs. On the other extreme, you can have up to two drawers, with 12 SSD drives each, for a total of 24 drives directly attached to System x servers via the ServeRAID MR10M SAS/SATA controller adapter.Read More]
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Perhaps the recent financial meltdown is making storage vendors nervous.Both IBM and EMC gained market share in 3Q08, but EMC is acting strangelyat IBM's latest series of plays and announcements. Almost cont
No, I think EMC is afraid that companies will discover what they already know, that IBM has quality products that would stand a fair chance of side-by-side comparisons with their own offerings.We have enough fear, uncertainty and doubt from our current meltdown of the global financial markets, don't let EMC add any more.
Have a safe and fun Halloween! If you need to add some light to your otherwise dark surroundings, consider some of these ideas for [Jack-O-Lanterns]!
technorati tags: IBM, DS5300, ESG, benchmarks, SPC, SPC-1, SPC-2, SPC-3, VMware, VMmark, Oracle, Orion, Microsoft, JetStress, EMC, BarryB, RAID-X, RAID-5, DMX, CLARiiON, Celerra, XIV, financial, global markets, crisis, meltdown, Halloween, Jack-O-Lantern[Read More]
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Fellow blogger Robin Harris over on Storage Mojo has a great post titled [Power-play, power work] wherehe points to Christian Belady's post [Changing Data Center Behavior Based on Chargeback Metrics].The focus is on metrics. The average data center is 10 to 15 years old, and the metrics used to chargeback IT expenses were often based on square footage.
The two main points in [Belady's presentation] were:
This is definitely a step in the right direction. Both servers and storage systems consume a large portionof the energy on the data center floor. IBM Tivoli Usage and Accounting Manager can includeenergy consumption as part of the chargeback calculations.Read More]