Getting to know SAS

Getting to know SAS

Don't you love it when a new technology moves from the drawing board to becoming real products? This is (finally) happening for SAS (serial attached SCSI), with several products coming to market in several areas.

In fact, Adaptec just added more SAS products to the ones I mentioned in an October column, as have several other vendors.

If you haven't been able to get your arms around this new technology quite yet, here is a quick summary that you may want to read.

Still find SAS confusing? Well, you're in good company, together with Network Appliance co-founder and CEO Dave Hitz, who -- according to his blog -- is also confused by SAS.

While staying focused on SAS' ultimate purpose may be tricky, there is nothing confusing about Adaptec's Snap Server 500, a new line of iSCSI block-serving and file-serving products announced this week.

This 1U box replaces the old Snap Server 4500 and comes in three versions, all mounting 64-bit AMD Opteron processors but with different levels of capacity, resilience, performance, and scalability. The top of the line Snap Server 550 has dual power supplies and can expand from just above 1TB to tens of terabytes, depending on the mix of SAS and SATA (serial ATA) drives used. It's interesting to note that to add more storage, you simply daisy-chain expansion modules to the main unit via SAS connections.

This model and the expansion boxes will began shipping in March, according to Adaptec. Expect to pay around $10,000 for a 550 with a 1.2TB capacity. The other two models, Snap Server 510 and 520, are available immediately starting at $3,600 and $4,600, respectively. All three Snap Server 500 models bundle the BakBone backup application, NetVault WorkGroup Edition, and eTrust Antivirus from Computer Associates, which could make them a very interesting offer for entry-level customers.

By contrast, large FC (Fibre Channel) customers may not like the idea of adding another connectivity protocol (like iSCSI) just for the sake of SAS. For those customers, a more suitable solution could be another storage array from Infortrend, also announced this week: the EonStor S12F-R1420, offering 4Gb FC connectivity and a backplane capable of hosting as many as 12 SAS (or SATA) drives from Fujitsu.

I don't know the details of their tests, but according to Infortrend the S12F-R1420 can sustain sequential writes at a rate of more than 500 MBps and performs at least 50 percent faster with sequential reads. I also find the new array's reliability specs noteworthy, including dual power supply and fans, battery backup modules, and UPS support.

Want another interesting example of SAS? Consider LeftHand Networks' recently announced support for the HP ProLiant DL380 G4 (Overview, Articles, Company) SAS Server. As you may remember, a long time ago LeftHand Networks opened its clustered network software, SANiQ, to run on different hardware platforms, a list that now includes the HP DL380 SAS. Check out the full specs of that server here, but don't overlook the new Smart Array SAS controller and the ability to mount small form factor drives, which translates into more efficient use of its 2U space as well as less heat.

My last (for now) example of a new SAS product is actually a new blade for the Finisar Xgig that adds support for SAS and SATA to this popular protocol analyzer.

I expect more products to crowd the market this year, but to avoid being confused keep in mind these easily remembered nuggets of truth about SAS:

1. SAS' primary mission is to replace old parallel SCSI devices, cables, and connectors in servers and storage arrays.

2. An SAS controller can host both SAS and SATA drives.

3. Because of nugget No. 2, new arrays can mount SAS and SATA drives indifferently, in mixed or separate enclosures.

4. Because of nugget No. 3, SAS could also take a bite out of the FC drives market.

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