5 ms·

Looking at the parts list I see the largest cost is the 2x 40-port SATA cards (aside from the drives). I wonder why they didn't decide to reduce the number of d

by jobu 13y ago

Looking at the parts list I see the largest cost is the 2x 40-port SATA cards (aside from the drives). I wonder why they didn't decide to reduce the number of drives to 40 so they could just use one SATA card and save $688?

deleted 13y ago
[deleted]
- kgermino 13y ago
  It's worth noting they only put 45 drives in the box so that extra $700 only gets you a 12.5% storage gain. However I suspect that splitting the drives between the two increases read/write performance and reliability as well.
atYevP 13y ago
Yev from Backblaze here -> Density is key! Our biggest need is to fit as much data as possible on each pod for as little price. The cost difference between removing 1 SATA card or removing 5 drives is negligible, but the added drives at another 20TB to the pod.
- dpe82 13y ago
  Why not use a smaller card (or the motherboard's controller) for the last 5 drives?
  - atYevP 13y ago
    We're constantly tweaking the design, that might pop up in the future!
- darkarmani 13y ago
  If density is your biggest issue, why don't you boot from USB and fit a 46th drive in there using the boot drive? Does that put you over heat or power budgets?
  - fragmede 13y ago
    or network/pxe boot
budmang 13y ago
That's an interesting idea. We considered trying to get rid of the extra card by mounting 5 drives either on the motherboard or on another card (and hope to experiment with these paths in the future.)
Vvector 13y ago
That was my first thought. But the math backs them up. You lose 12% capacity per chassis. But you only save 7% per chassis ($688 off of $9305). So they would end up paying more for extra pods just to get the same storage. This doesn't include the rack space cost.
- dcuthbertson 13y ago
  Nitpick: In addition to the savings of $688 for the SATA card, you also have to include a savings of about $1400 for the five 4TB drives that won't be included. That bumps the savings on the pod to just over 22%. Still, at least 12% extra rack and floor space to get the same storage capacity would probably cost them more in the long run.
  - greedo 13y ago
    In the article, they say the average cost of their 4TB drives is $160, so the savings from removing the five drives would only be $900, not $1400.
jccooper 13y ago
Rack space is an ongoing cost while the hardware is a fixed cost. Presumably they've decided it's worth having a slightly higher fixed cost per GB in exchange for a reduced ongoing cost per GB. (There's probably other benefits as well, such as reduced workload and just getting the space online now.) Let's take a look... They do have an oldish post on hosting costs: http://blog.backblaze.com/2011/07/20/petabytes-on-a-budget-v2-0revealing-more-secrets/ http://blog.backblaze.com/2011/07/20/petabytes-on-a-budget-v... A rack in 2011 cost them $2,100 per month (it's more now, guaranteed). Their racks look to hold about 11 machines. Each pod is then about $191/mo. Each rack thus needs 1.375 extra pods at "low density". That's $262.50 a month. Since you now need about 10% more pods, you're paying about $29 more in hosting costs per month per pod. Your savings are not $688, since you also need to construct 1/8 pod later. A low-density pod will cost about $2719, with is $340 split 8 ways. So real hardware savings is $348. Hosting costs eat that in exactly a year, and they are certainly expecting a longer life than that. (That's 2011 hosting costs, which are certainly lower.) So it's worthwhile to spend a little extra for the additional drives. (Of course, if they could get the extra five in with more modest hardware, as seems quite possible, that would be a sure win. But sometimes ease of development/assembly/spare parts wins over hardware cost.)

by jobu 13y ago

deleted 13y ago

[deleted]

kgermino 13y ago
It's worth noting they only put 45 drives in the box so that extra $700 only gets you a 12.5% storage gain. However I suspect that splitting the drives between the two increases read/write performance and reliability as well.

atYevP 13y ago

Yev from Backblaze here -> Density is key! Our biggest need is to fit as much data as possible on each pod for as little price. The cost difference between removing 1 SATA card or removing 5 drives is negligible, but the added drives at another 20TB to the pod.

dpe82 13y ago
Why not use a smaller card (or the motherboard's controller) for the last 5 drives?
- atYevP 13y ago
  We're constantly tweaking the design, that might pop up in the future!
darkarmani 13y ago
If density is your biggest issue, why don't you boot from USB and fit a 46th drive in there using the boot drive? Does that put you over heat or power budgets?
- fragmede 13y ago
  or network/pxe boot

budmang 13y ago

That's an interesting idea. We considered trying to get rid of the extra card by mounting 5 drives either on the motherboard or on another card (and hope to experiment with these paths in the future.)

Vvector 13y ago

That was my first thought. But the math backs them up. You lose 12% capacity per chassis. But you only save 7% per chassis ($688 off of $9305). So they would end up paying more for extra pods just to get the same storage. This doesn't include the rack space cost.

dcuthbertson 13y ago
Nitpick: In addition to the savings of $688 for the SATA card, you also have to include a savings of about $1400 for the five 4TB drives that won't be included. That bumps the savings on the pod to just over 22%. Still, at least 12% extra rack and floor space to get the same storage capacity would probably cost them more in the long run.
- greedo 13y ago
  In the article, they say the average cost of their 4TB drives is $160, so the savings from removing the five drives would only be $900, not $1400.

jccooper 13y ago

Rack space is an ongoing cost while the hardware is a fixed cost. Presumably they've decided it's worth having a slightly higher fixed cost per GB in exchange for a reduced ongoing cost per GB. (There's probably other benefits as well, such as reduced workload and just getting the space online now.) Let's take a look... They do have an oldish post on hosting costs: http://blog.backblaze.com/2011/07/20/petabytes-on-a-budget-v2-0revealing-more-secrets/ http://blog.backblaze.com/2011/07/20/petabytes-on-a-budget-v... A rack in 2011 cost them $2,100 per month (it's more now, guaranteed). Their racks look to hold about 11 machines. Each pod is then about $191/mo. Each rack thus needs 1.375 extra pods at "low density". That's $262.50 a month. Since you now need about 10% more pods, you're paying about $29 more in hosting costs per month per pod. Your savings are not $688, since you also need to construct 1/8 pod later. A low-density pod will cost about $2719, with is $340 split 8 ways. So real hardware savings is $348. Hosting costs eat that in exactly a year, and they are certainly expecting a longer life than that. (That's 2011 hosting costs, which are certainly lower.) So it's worthwhile to spend a little extra for the additional drives. (Of course, if they could get the extra five in with more modest hardware, as seems quite possible, that would be a sure win. But sometimes ease of development/assembly/spare parts wins over hardware cost.)