SSD vs. SAS vs. SATA

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So the new server is almost done. It's going to be 32G per motherboard for a total of 64G, not 64G per motherboard for a total of 128G as previously reported. Turns out you can only run 4 quad-rank modules per quad-core opteron, and dual-rank 4G modules cost north of twice as much per gigabyte.

But I've got the ram on my kitchen counter, and the server in the garage. All I'm waiting on is the disk and the last 2 CPUs, neither of which I've bought, waiting for the latest consulting check to clear.

so, I need disk. I've got 2x3.5" bays per motherboard in this server. I was initially planning on just mirroring those new Seagate 1.5TB sata disks, but I'm a little concerned with performance, so I'm exploring the alternatives.

The advantage of the sata, of course, is the cost-per-gigabyte. we're talking around $360 for 1.5TB of mirrored space. performance is pretty awesome, too, at least for sequential access. But this isn't sequential access, so I'm a little concerned that 2x SATA spindles isn't going to cut it, performance wise.

Now, one option is to just put in a pair of 300GB 10Krpm SAS disks. about the same price for disk, add another $150 for a cheap supermicro sas card. But this means I give out considerably than 10G of disk for every 1G of ram. Considering that most of my customers are in the 256-512M range, that's not much disk. and if I want 15Krpm, that's twice as much cash. ouch.

So here is what I was thinking... for around $200 I can get a single 64G sata-attached ssd. now, these things aren't particularly fast for sequential transfers, but for random access, they are awesome. Just what I want. More to the point, those SSDs are tiny, and don't need to be mirrored for reliability. I can fit them in the space reserved for the cdrom drive, so I could use the 64G ssd card and the mirrored sata. you'd get around 2G ssd for every 1G ram you bought, and around 40GB of sata per gigabyte of ram.

So yeah. my only worry with the 64G SSD card/1.5TB sata arrangement is that it is more complex, I mean, you have one fast disk and one slow disk.

I'm still thinking of a storage server that will let me give customers disk via iscsi or AoE or something... but last time I looked, it was all either expensive, unreliable or slow. I'll experiment and see what I come up with.


I'm still thinking of a storage server that will let me give customers disk via iscsi or AoE or something...

that's exactly what i would want!

yeah. no question it would be awesome, if it worked. But as far as I can tell, storage is either expensive, unreliable or slow. Now, it has been a while since I've looked at it, so maybe sofware iscsi is OK now? I dono. it does require some looking, though.

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