Sun beefs servers with SSDs
Server maker Sun Microsystems took a shining to flash-based solid state disks (SSDs) in late 2007, and today, it will finally announce SSD modules that plug into its entry and midrange server lineup.
The company has already put SSDs in its "Amber Road" storage arrays, launched last November as the not-so-tersely named Sun Storage 7000 Unified Storage family. (Yes, they said "storage" twice). And now, the company is adding SSDs to Sun's "Galaxy" x64 servers, its "Niagara" family of Sparc T series servers (sometimes referred to as the CMT line, short for chip multithreading), and its Sun Blade blade servers, which are based on x64 and Sparc T processors.
While Sun is working with a number of different flash storage vendors on the design of future flash devices - including Intel, Samsung, Marvell, and Toshiba - today's announcements involve Sun using Intel's X-25E SATA-compatible flash memory. (These are the same Intel SSDs that server maker Verari Systems put on its storage blades last October).
The X-25E comes in a normal 2.5-inch SATA form factor, which Sun has wrapped some packaging around so it can either plug into hot-swap disk drive bays. The SSD has been shipping with 32 GB capacity from Intel since last October and is expected to be released with a 64 GB capacity any day now.
The X-25E is based on single-level cell (SLC) flash memory technology and is able to process 35,000 I/Os per second (IOPS) on reads and 3,300 IOPs on writes. This is a lot more IOPS than a 15K RPM SAS hard disk drive can deliver, says John Fowler, general manager of Sun's Systems Group, which he says comes in at around 320 IOPS. That speed differential is one reason why Sun has added flash drives (not from Intel) to the Amber Road storage arrays.
The other is that Sun's Solaris Unix and its related Zettabyte File System (ZFS) have been tweaked to create hybrid storage pools of hard disks, SSDs, and main memory, so that frequently accessed data is parked in memory or SSDs to speed up system performance.
In servers, ZFS is going to come in handy for another reason. "A single SSD can exhaust a RAID controller," says Fowler. So you can imagine what hanging four, six, eight, or a dozen might do. But because ZFS has its own data protection algorithm, called RAID Z, that runs as software on a server, customers can opt out of using RAID controllers and just use SATA or SAS ports linked directly to the I/O bus. There is no RAID chip to saturate. (Fowler didn't mention how much CPU capacity a server with lots of SSDs might need for ZFS to do its thing).
Not that Sun is suggesting server customers should unplug all of their hard disks and replace them with flash-based SSDs. For one thing, at a list price of $1,199 for one of Sun's hot-plug SSD modules (presumably at 32 GB, and representing a nearly 2X mark up over Intel list for the raw SSD unit), server buyers won't be able to afford that. But for another, SSDs are supposed to be sprinkled onto systems, not stuffed into them up to the gills.
To help customers strike the right balance, Fowler says that Sun is putting the finishing touches on a capacity planning tool for SSDs that will allow customers to run the tool on their production systems as they are working and then make suggestions about how much flash to add to their servers and how to moved their files around to improve performance. Having done that, customers can keep running the tool to keep tuning.
The one thing that is clear is that having two orders of magnitude of performance on reads and one magnitude of performance on writes - even with one order of magnitude higher cost - means that SSDs are going to absolutely become standard on servers.
In a separate but related announcement, Sun has released the design of the open flash module into the storage community at its OpenSolaris project. This module, which puts flash memory on a Mini-DIMM format, comes in a 24 GB capacity and prototypes were made by Sun using Samsung flash memory.
Sun's flash guru, Michael Cornwell (formerly of Apple iPod fame), has been working with flash memory makers and other interested parties to push the open flash module Mini-DIMM format for future servers because the Mini-DIMM is a lot smaller than a disk drive and allows better air flow inside the server chassis.
A Sun spokesperson said that Sun plans to put these Mini-DIMM flash-based drives into storage arrays "within the next couple of months." Presumably servers will get sockets for these as well as skip the disk drive format altogether. It is also a fair guess that the Sparc64-based systems made by Fujitsu and resold by Sun will get some sort of SSD goose, and you can bet that SSDs will be part of the "Supernova" server launch based on the "Rock" UltraSparc-RK processors, due in the second half of this year.
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