Three Questions: (boot times, drive-adding/size philosophy, & parity drive perf)

[nightfly]

I apologize in advance for what will likely be a long post. I'll ask my questions and then give the back story of my situation should any of you be interested.

 

1) How fast do most unRAIDs boot? Is the flash the bottleneck?

 

2) Have any of you figured out a formula for figuring hard drive upgrades? I mean something like 'only buy a larger size drive if you're willing to buy 2 or more' or 'better to buy more of the same size drives unless...' I'm sure many of you guys have put more thought into it than me. I'm also interested whether you calculate on the basis of $/gb or watts/gb or #drives/gb etc. in weighing out options.

 

I'm happy to see that 750gb drives are coming very close to 500gb prices in $/gb (saw one $155 shipped today). This guy had only a 16mb cache. Maybe that's where all of them are at and only higher end 1TBs have 32mb, but here's my third question:

 

3) Does the cache size on parity disk impact performance? Should one buy a 'higher end' SATA for the parity drive because it's the workhorse?

 

Now I'll spammily explain why I ask these 3 questions. How fast does it boot? I'm trying to decide whether to build an unRAID system now in my present house in India (where we have 6h daily scheduled power outages) or wait for 7 months more when we move into a different city with only 2 hours a day. I *could* leave it on here 24/7 like I do my Mac Pro thanks to my new 3.5kva battery backup system, but if it booted in 10-20 seconds, then the answer is pretty easy - boot it when I need to write to it or stream from it, otherwise leave it off.

 

I need to decide whether I'm doing it now or later shortly, because I have a number of friends coming to visit (from our church back home) and bringing us several suitcases of goodies that we'll order online. If I was to include $400 of newegg parts (everything but drives and a case) now would be the time to order it.

 

About the formula for upgrades, I'm wondering if/how many drives I'd need to add to start off. I think a lot, as I presently have 900+GB of HD movies on a mostly-full external GigE 1TB Lacie drive (2x500GB inside). In fact, most all of my drives are pretty full, so dumping them and then re-incorporating them into the array will be tricky. In addition to these two, I have 2x120gb IDE drives sitting around and a 400gb IDE. I think I'd have to add at least 2x 750GB drives to even offload my data and get started, although I do have 300GB free on my Mac Pro that I could temporarily store stuff on. I don't think I'll change the internal configuration of my Mac Pro, with the stock 250GB system drive and 500GB storage drive. But I'd be tempted to maybe just get a 750GB, swap it into my Pro and then take the 2 drives out of it, making 500GB the biggest drive and parity drive (for now). I can't imagine anyone's actually followed my rambling, but I'll finish the final part.

 

How big a part does disk performance play for a parity drive? Just wondering if I should get the cheapest possible $/GB across the board or 'invest' a bit more in a higher-end/spec'd drive for parity.

 

Thanks for your patience!

Alex

[nightfly]

So... was the Lounge the wrong place to ask these questinos? Any suggestions?

[bubbaQ]

The boot takes about a minute or so for me.  USB is only part of it, and the it is affected by whether you have USB1 or USB2, the size of the initramFS, and CPU.  Most all of th it is the Linux boot... unRAID only takes a few seconds at the end.  After the init load, speed depends on is disk and CPU.  This is not like a Novell boot, where each volume has to be checked while mounting and can take a long time.

 

Here is what I would to:

 

- Get 2x750GB.  Start your unRAID with them BOTH as data disks.... no parity.

- Copy the contents of the Lacie drives to unRAID.

- Dismantle the Lacie and take the drives out.

- Add the Lacie drives to unRAID as data disks

- Copy data from ONE of the 750GB drives to the 500GB data disks, then make that 750GB drive Parity

- you will have enough room to copy the other drives (120gb and 400gb) one at a time to the array, then add them as data disks.

- Do biggest drives first.

 

Don't worry about performance.  Any drive will work fine for 99% of people's needs.  For most people, the performance issue is like the performance of a BMW over a Yugo when you are only driving to the end of the block.  There is a difference, but not one worth considering for most people.... particularly budget conscience people.

 

 

 

 

[nightfly]

Spectacular response! Thanks for taking the time to understand my situation.

 

Any thoughts of drive-adding philosophy?

[nightfly]

So I go to Newegg and I see that Samsung Spinpoint 750s are 32mb cache vs the cheapest WD jobbers that are 16mb (and $15 cheaper). Since one of these will be the parity, don't think there's any advantage to the 'higher end' drive? I'll probably get at least 1 Samsung (for Parity) because I bought a 500gb Samsung drive for my Mac Pro and like it - quiet, but probably more case engineering than drive superiority

 

Thanks!!!

[nightfly]

So as I added up my shopping list I started wishing I could just add 2x500s instead, but I don't think it could work - your math was helpful.

 

Then I started to philosophize, really the only time to 'move up' to a bigger drive is when you're ready to buy 2 of them - unless you upgrade now knowing that it'll be incrementally cheaper to upgrade further in the future - but in this market that doesn't make much sense.

 

I must admit, I'm balking at the sticker price of starting from scratch. Wishing I hadn't sold off my old P4 gaming rig a couple years ago when I went all Apple. Here's my list (I can paste the fuller list with newegg links if any wishes)

 

$35 low-end crap Indian-made case supporting 10 3.5” drives (with cage below)

$65 PSU

$35 CPU

$105 MOBO

$30 Memory

$20 cage

$350 2x750 samsungs

 

$120 unRAID license

 

$760 total (for 2.4TB usable over 8 drives)

 

[bubbaQ]

You don't have to buy 2 to make an upgrade worthwhile.  A lot of people forget if you upgrade parity to a new drive large than all the others, you get to recycle to OLD parity drive.... so the only "wasted" space is the delta on the parity drive.

 

Suppose you do the rig as planned.  In 6 months you need more space.  You can either buy:

 

750GB for $175 and keep parity same

1TB  for $225 and swap parity to data and use new drive for partiy

 

If you buy EITHER one, you get 750GB more data space.  So if the sweet spot moves, you can buy in the price of the new speetspot, and get the space of the old sweet spot.  So there is about a 20% premium on the first drive when you move to larger drives in unRAID.  Your second buy in the sweet spot has no premium.  So if you spread the premium over 2 drives, you pay 10% more per drive for 2 drives.  Just wait for a good sale.