I am looking at buying three servers, and trying to figure out which storage solution makes the most sense in terms of performance and cost.

Total budget is around: $10,000.

OPTION 1: Dell servers with RAID 10 (4 Drives) each 7200RPM SAS 500GB, for a total capacity of 1TB. Each server is approx: $3000. Total storage then across all three servers is 3TB.

OPTION 2: Same Dell servers with a cheap single drive no RAID for $2000 and go with a centralized SAN solution.

The biggest problem is that I haven't been able to even find a SAN solution that is a reasonable price. Dell entry level storage servers are like $15,000. I am thinking just iSCSI, not fiber (too expensive).

What do you guys recommend?


My reading of the tea-leaves says you're looking for space more than you're looking for performance. Your choice of 7.2K RPM drives, and 500GB ones at that, also suggest cost is a driver.

What operating system you're planning on accessing this storage makes a big difference as well.

You may be better served with a dedicated iSCSI NAS device similar to the Drobo Pro and fill with higher capacity, but faster and reliable, drives. You can get to 3TB pretty fast even with 10K RPM drives. Depending on how hard you squeeze your vendors you just might be able to eek it within your budget.

  • Yes, I would love to use 10K or 15K RPM drives, but its cost prohibitive. The servers are going to be virtualized using Xen, and running CentOS 5.5 x64. – Justin Jan 5 '11 at 23:17
  • Drobo looks like the ticket, but think we need Elite, to support multiple servers accessing the single share. – Justin Jan 5 '11 at 23:38

SAN is going to be expensive. With your budget you can't afford it.

  • Why are SAN setups so expensive? Shouldn't it just be a RAID card, cheap CPU and minimal memory and then disks? – Justin Jan 5 '11 at 23:13
  • SANs are a lot more that just RAID card with ethernet ports. They need lots of memory for read and write caching. Large batteries for flushing to disk in case of a power failure. The ability to take snapshots, create clones, replicate data between arrays, etc. More advanced units integrate with things like VMware to reduce network traffic between storage and servers when moving files around the array, etc. – mrdenny Jan 5 '11 at 23:16

With a budget of 10K you're not going to get a SAN and servers, get over it.

As to how you organise the disks, whether you should go for serial ATA / SCSI internally, or a shared SCSI enlosure, or iSCSI then it all depends on the workload you're using the servers for - file serving, database, email, web.....and your operating system too. But you've not mentioned any of these.

  • Its for VM instances, all running CentOS 5.5 x64. The three servers are virtualized using XEN. – Justin Jan 5 '11 at 23:14
  • OK - but what do they serve – symcbean Jan 5 '11 at 23:21

Most SANs are Fibrechannel, optical transceivers, gigabit links; it seems you're more interested in raw storage rather than performance and predictability. A SAN would not fit your budget, but a Drobo or other NAS would. You'll not have the predictability of a SAN, but you'll come in under-budget.

The best way to think of a SAN is an extension of your SCSI bus to more devices. SCSI-on-FC is merely running that at (8g) 800MByte/sec, or (16g) 1600MByte/sec, but still talking SCSI. The difference from Fibrechannel to iSCSI is that SCSI-in-FC tends to "ask first": "I have 16k to write, do you have room?" "yes, ready for transfer" "OK, here it is". iSCSI is on ethernet, which tends to shoot first, check for collision/errors after. That works when you're not nearing 100% utilization, tends to work with cheaper transceivers, even though iSCSI LANs tend to be kept separate from TCP LANs.

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