SAS or SATA 4 Servers

[owen1978]

I work in primary schools, and at most these schools have about 150 client machines.

But in terms of concurrent users probably 60 machines.

 

They server normally tends to be the pdc,dhcp,dns,file & print server.

Curriculum servers dont tend to have a intense database, the only database on curric servers

tend to be the Abacus Intertactive Planner database.

 

Most of the stuff tends to be roaming profiles, doucments and in terms of programs they run off a share. Would SAS be overkill for such a system?

 

Im running some performance monitors;

 

Physical disk: idle time

Physical disk: queue length

Physical disk: disk write time

 

are there any other monitors i should be looking at?

And what are your opinions on SAS vs SATA, if i was working at a secondary school or higher then I would go SAS all the way, but primary schools tend to be lighter.

[Michael]

SAS does give better performance, but is also a lot more expensive. With the example you have given using multiple SATA2 disks in a hardware RAID1 or RAID5 setup would be absolutely fine.

[mattstevenson2005]

if your one server is doing all that then i would really suggest SAS drives, im at a secondary school with around 150-200 concurrent users all day with 24 servers and all the servers have local SAS drives for their system drives. So if your one server is doing all that work you should have SAS

[AIT]

 

Most of the stuff tends to be roaming profiles, documents and in terms of programs they run off a share. Would SAS be overkill for such a system?

 

 

Paging files is another good monitor.

Average disk queue is probably the most important. If this is high then sas would be beneficial.

 

 

sas would not be over kill for the c drive or even roaming profiles if you can aford it.

However for the small number of users sata would be far more cost effective specially if raided.

[RobFuller]

I would probably go with SATA and just buy as many disks as the unit can take to spread the load. But considering the costs differences I don't think a primary would really see the benefit plus you can get much high capacity disks, just backup then becomes more interesting.

[dyoung5]

I would suggest that you save the money and get SATA. Our file server which servers 1500 pupils with average of 300 concurrent users has SATA in RAID 5, and while it isn't really fast, it does do the job nicely.

 

Make sure you RAID it to give redundancy and better performance. Use the money you save from SAS to buy more disks, and setup seperate arrays for the AD/DNS/DHCP, etc and the file stores to get better performance.

[AIT]

I would suggest that you save the money and get SATA. Our file server which servers 1500 pupils with average of 300 concurrent users has SATA in RAID 5, and while it isn't really fast, it does do the job nicely.

 

Make sure you RAID it to give redundancy and better performance. Use the money you save from SAS to buy more disks, and setup seperate arrays for the AD/DNS/DHCP, etc and the file stores to get better performance.

 

i agree.

 

1400 students. 10 sata drives raid 5. excellent performance. much better than the old 15k sas.

[owen1978]

In terms of the roles the server plays as a pdc, dns, dhcp these would hardly bother the disk and would be cpu intensive instead.

[fafster]

And don't forget to enable write caching.

[m25man]

Looks like we have the old SAS SATA split forming in this thread.

 

I don't think its a performance issue any more is it!

 

The more disks in an array means the data has to be stripped across them any way with BBWC cache controllers the performace loss seems to be minimal for what most schools would use them for.

 

Reliability is another issue. SATA does not have the same proven track record as some of the SCSI/SAS devices and the quality of the SAS drives seems to fall off remarkably as they get cheaper.

 

HP only offer 1 year warranty on SAS drives even though the same hardware can be found with a 3/5 year warranty from the OEM's.

 

I personally have replaced far fewer SCSI/SAS drives in Comparison to SATA drives in all of the years I have been in frontline support.

 

As a result I look to the Big Boys for guidance and you will always see that for critical data they use SAS/SCSI and for the less important or easily resotrable data, SATA.

 

Hey, in some SAN's they mix them SAS on the Live Arrays SATA on the backup/Mirrors.

 

So IMOHO, I choose SAS for my critical servers and SATA for the ones that I can afford to run without whilst I find time to restore them.

 

As always cost will be an overiding factor as budgets get tighter.

[owen1978]

Looks like we have the old SAS SATA split forming in this thread.

 

I don't think its a performance issue any more is it!

 

The more disks in an array means the data has to be stripped across them any way with BBWC cache controllers the performace loss seems to be minimal for what most schools would use them for.

 

Reliability is another issue. SATA does not have the same proven track record as some of the SCSI/SAS devices and the quality of the SAS drives seems to fall off remarkably as they get cheaper.

 

HP only offer 1 year warranty on SAS drives even though the same hardware can be found with a 3/5 year warranty from the OEM's.

 

I personally have replaced far fewer SCSI/SAS drives in Comparison to SATA drives in all of the years I have been in frontline support.

 

As a result I look to the Big Boys for guidance and you will always see that for critical data they use SAS/SCSI and for the less important or easily resotrable data, SATA.

 

Hey, in some SAN's they mix them SAS on the Live Arrays SATA on the backup/Mirrors.

 

So IMOHO, I choose SAS for my critical servers and SATA for the ones that I can afford to run without whilst I find time to restore them.

 

As always cost will be an overiding factor as budgets get tighter.

 

I undestand, but in a primary school scenario, the amount of abuse the SATA will get is considerably less thus hopefully it will last longer?

[tmcd35]

Built a couple of servers for local primary/infant schools of late. We tend to be going for a couple of 300Gb WD 10krpm SATA drives in RAID-1. Seems to be giving the schools the space they need and the drive access speed for the number of users.

[chazzy2501]

SAS drives are a whole different breed of harddrive and I would highly recommend SAS drives for your OS atleast. SAS drives use more bits per sector for a higher fault tolerance they're also designed to cope with vibration (ringing) better and go through a higher level of testing. A SATA drive must endure scrubbing (in a raid) and it's sectors are 10x more likley to fail compared to a sas drive (a real issue in a RAID environment (during a rebuild).

 

I say all this but I do have a raid 5 sata array for file storage in my SAN (4x1TB), I couldn't afford 3TB SAS storage.

 

I do have a raid 5 SAS storage for the OS'es. 3x450GB.

 

I have a very complex paper on this very issue I'll have to dig up the link.

[jsnetman]

im at a secondary school with around 150-200 concurrent users all day with 24 servers

 

Hmm sounds like overkill to me. We have 350 curriculum machiines which means a possibilty of 350 concurrent users and we only have 2 servers. But getting back to the thread we just got some sas drives this summer in our new servers and I'm very impressed.

[m25man]

I undestand, but in a primary school scenario, the amount of abuse the SATA will get is considerably less thus hopefully it will last longer?

 

Data is just Data, I don't think abuse comes into it.

 

SATA Drives are mass produced and are cheap, there are Enterprise Level SATA drives that claim to be of a higher quality and get 5 year Manufacturer warranties but you only need to look at THIS search result to see what can happen to your data!

 

[owen1978]

Think im leaning towards SAS, which leads me to ask which HP SAS Raid card do you recommend & Battery Backup Unit?

[maark]

have had problems with a few sata based servers but never sas ones - they would be better for OS if you can afford it.

[Arthur]

Built a couple of servers for local primary/infant schools of late. We tend to be going for a couple of 300GB WD 10krpm SATA drives in RAID-1. Seems to be giving the schools the space they need and the drive access speed for the number of users.

If you have some of the earlier 300GB WD Velociraptor's and run them 24/7 in a RAID environment you may be interested in this thread. It seems they have a firmware bug where they falsely report errors to the RAID controller/host OS after 49 days of continuous operation. The firmware update can be downloaded from here or by contacting WD support. Newer Velociraptor's should already have this firmware.

 

Personally I would go for SAS drives in servers for reliability and performance reasons (at least for the operating system). Some of the common differences between enterprise-class SAS/SATA disks and desktop SATA disks are listed below (Source):

 

• Warranty - Desktop drives usually have a 3-year (or less) warranty, while Enterprise drives usually have a 5-year warranty (IIRC, some of the Samsung drives have a 7-year warranty).
  
• MTTF/MTBF - This calculated value is an estimate of the number of hours until the drive fails, and is only valid for the warranty period. For Enterprise drives, it's usually higher than for their Desktop counterparts.
  
• Error Recovery - This is called various things by various manufacturers (TLER, ERC, CCTL). In a Desktop drive, the goal is to do everything possible to recover the data. In an Enterprise, the goal is to ALWAYS return SOMETHING within the timeout period; if the data can't be recovered within that time, let the RAID controller reconstruct it.
  
• Bit Error Rate - This is a statistical measure of how often an error (either recoverable or unrecoverable) will occur. The rate for Enterprise drives is usually lower than for Desktop drives.
  
• Vibration resistance - When several disks are in a single chassis, the vibration from one or more of the drives can affect the others. Some Enterprise drives have firmware (with sensors?) that specifically reduces the effect of this vibration on the error rate. On those drives where this is done, it can sometimes be seen as a difference in the vibration specs of the drive.
  
• Target market segment - Desktop drives are designed for 5x9 operation with light use, while Enterprise drives are designed for 7x24 operation with heavy use. I believe this effects the motor & voice-coil drive electronics, possibly the overall disk heatsink capabilities, and possibly the operating temperature range of the drive.
  
• Request Queuing - Enterprise drives usually have improved queuing algorithms for I/O requests. This gives more IOPS as the load increases (something you're not likely to see in a lightly loaded Desktop usage).
  

[dmiller]

I generally go with the following SAS for OS mirror 80gb then Raid 5 3 1tb sata.

 

However if this is a high demand Server eg video editing scratch server then mirror 80gb sas then raid 5 sas according to requirements.