Advice BEFORE you buy your first NAS

[ed.j]

Not sure if there is already a thread like this, but it could be helpful to include generic advice that wouldn't necessarily come through on the acquisition advice threads.

The advice I would give to someone is that if they are buying a NAS with more than two bays, and they want to use Synology Hybrid Raid (ie have redundancy built in for a single disk to fail), is do NOT fill each of the drive bays from the get go. Buy TWO of the biggest drives you can, use SHR, and add (an)other large drive(s) when you need the space.

I bought a DS920+ and thought it was sensible to use 4 x 4TB drives with SHR (so 10.5TB usable space). Now to increase the space I need to sell/repurpose two of the drives (as SHR needs at least of the largest capacity drive to maximise it's potential). If I had bought 2 x 10TB drives, I'd have more or less the same amount of space and could wait a while before having to buy a new 10tb drive - which would double the space available.

In short: Do not aim to fill all of the bays from the get-go. Buy a small number of large capacity drives, and add drives as you go on.

RAID Calculator | Synology Inc.

Use this interactive tool to estimate the storage space of your Synology NAS when paired with different size hard drives and RAID levels.

www.synology.com

 

[maravac]

Not sure if there is already a thread like this, but it could be helpful to include generic advice that wouldn't necessarily come through on the acquisition advice threads.

The advice I would give to someone is that if they are buying a NAS with more than two bays, and they want to use Synology Hybrid Raid (ie have redundancy built in for a single disk to fail), is do NOT fill each of the drive bays from the get go. Buy TWO of the biggest drives you can, use SHR, and add (an)other large drive(s) when you need the space.

I bought a DS920+ and thought it was sensible to use 4 x 4TB drives with SHR (so 10.5TB usable space). Now to increase the space I need to sell/repurpose two of the drives (as SHR needs at least of the largest capacity drive to maximise it's potential). If I had bought 2 x 10TB drives, I'd have more or less the same amount of space and could wait a while before having to buy a new 10tb drive - which would double the space available.

In short: Do not aim to fill all of the bays from the get-go. Buy a small number of large capacity drives, and add drives as you go on.

RAID Calculator | Synology Inc.

Use this interactive tool to estimate the storage space of your Synology NAS when paired with different size hard drives and RAID levels.

www.synology.com

but... more drives = better throughout speed (faster disk r/w). Am I right or not?

 

[Coop777]

with disk arrays I think the reverse is true actually... data spread across a larger number of drives takes longer to process, rather than spread across a lower number of drives.

 

[Robbie]

but... more drives = better throughout speed (faster disk r/w). Am I right or not?

Yes.

with disk arrays I think the reverse is true actually... data spread across a larger number of drives takes longer to process, rather than spread across a lower number of drives.

No.

The advice I would give to someone is that if they are buying a NAS with more than two bays, and they want to use Synology Hybrid Raid (ie have redundancy built in for a single disk to fail), is do NOT fill each of the drive bays from the get go. Buy TWO of the biggest drives you can, use SHR, and add (an)other large drive(s) when you need the space.

In short: Do not aim to fill all of the bays from the get-go. Buy a small number of large capacity drives, and add drives as you go on.

My advice would be more needs-based for a multi-bay NAS.

Very large drives are more expensive, have a lower throughput and lower IOPS with higher latency and make more noise - all when compared to a larger array of smaller disks.

As for starting with 2 very large drives and adding more as needed the user will be committed to adding drives at above the size already fitted. You can go up, but not down in size.

My final point that concerns all of us with these massive HDDs released in the last few years is that the explosion in capacity has not been matched by either the interface speed or the read/write warranty. This means for RAID rebuilds and alike the process can easily take a day, sometimes more. With the drive thrashing associated with such activity the risk of a further failure is way higher than we had just a few years back. This is what lead to RAID 5 being depreciated as the risk vs recovery failure became too high; the risk has only increased since then.

Clearly I am not saying that fitting smaller drives is always the way ahead either. It has to be a needs-based choice where purpose, type, performance, redundancy, budget, risk and environment all trade off against each other. I would suggest that a default position of buying the minimum number of the biggest drives you can would be foolhardy.

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[Rusty]

Couldn’t have said it better.

 

[ed.j]

Very large drives are more expensive, have a lower throughput and lower IOPS with higher latency and make more noise - all when compared to a larger array of smaller disks.

To be honest I am approaching this from the point of view of someone who isn't trying to eke out the absolute top performance from their disks, I think that is a small fraction of users. If someone is concerned with those types of metrics, they probably aren't a first time user, and probably wouldn't refer to this thread (as it was intended anyway )

As for starting with 2 very large drives and adding more as needed the user will be committed to adding drives at above the size already fitted. You can go up, but not down in size.

You can go up and down in size - with SHR anyway.

For the sake of ease, I will use my setup as an example - DS920+, wanting about 10TB of storage, with the potential to increase later on, using SHR.

Taking the current prices for WD Red Pro on Amazon UK and storage space from the RAID calculator...
1) 4 x 4TB = 4 x £130 = £520. 12TB space, £43 / TB
2) 2 x 10TB = 2 x £303 = £606. 10TB, £60 / TB

If you want to add another c. 10TB of space,
1) Buy 2 x 10TB = 2 x £303 = £606. 18TB of space. Add on the cost of the first 4 and you get £1126, £63 / TB
--- If you sell the 2 x 4TB HD you no longer need for say 50% of the purchase price (bit of a guess here), total cost = £996, £55 / TB
2) Buy 1 x 10TB = £303. 20TB of space. Add on the cost of the first two and you get £909, £45 / TB

So it ends up being slightly more expensive to start with but will end up cheaper as you go on, even if you sell the old drives. And there's no faff of having to sell or having old drives being unused.

My final point that concerns all of us with these massive HDDs released in the last few years is that the explosion in capacity has not been matched by either the interface speed or the read/write warranty. This means for RAID rebuilds and alike the process can easily take a day, sometimes more. With the drive thrashing associated with such activity the risk of a further failure is way higher than we had just a few years back. This is what lead to RAID 5 being depreciated as the risk vs recovery failure became too high; the risk has only increased since then.

Clearly I am not saying that fitting smaller drives is always the way ahead either. It has to be a needs-based choice where purpose, type, performance, redundancy, budget, risk and environment all trade off against each other. I would suggest that a default position of buying the minimum number of the biggest drives you can would be foolhardy.

I am assuming that because SHR is being used, drive failure is less of a problem.

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Admittedly just looking at the price of WD Red Pros on Amazon is a small sample. Using Seagate Ironwolf prices on box.co.uk....

1) 4 x 4TB = 4 x £84 = £336. 12TB space, £28 / TB
2) 2 x 12TB = 2 x £289 = £578. 12TB, £48 / TB

If you want to add another c. 10TB of space,
1) Buy 2 x 12TB = 2 x £289 = £578. 20TB of space. Add on the cost of the first 4 and you get £914, £46 / TB
--- If you sell the 2 x 4TB HD you no longer need for say 50% of the purchase price (bit of a guess here), total cost = £830, £42 / TB
2) Buy 1 x 12TB = £289. 24TB of space. Add on the cost of the first two and you get £867, £36 / TB

.... so luckily my maths/assumptions hold for this combo too.

However I appreciate it isn't all about cost.

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Basically I wish I hadn't filled out all the drive bays on my 920+ right away!! Maybe this thread was a little moan shrouded in some "advice"

 

[Robbie]

You can go up and down in size - with SHR anyway.

No, you are mistaken.

I am assuming that because SHR is being used, drive failure is less of a problem.

No, SHR is RAID 5 in a posh frock. Underneath it is Linux RAID 5 (once above 2 drives). Same goes for SHR 2 & RAID 6.

 

[Telos]

You can go up and down in size - with SHR anyway.

Smaller drives would require a new, second pool.

 

[ed.j]

Apologies for the misinformation - thanks for correcting me

Point stands re costs though

 

[Robbie]

Point stands re costs though

Not completely as you are missing out on the 3 drive option, leaving the 4th free for expansion (presuming that is a 4-bay). When the time comes for expansion using the 4th bay comes the point where the SHR options come in play.
Typically the 4th drive would be of higher capacity, giving you expansion and 'x' amount of dead space. When the next round of expansion comes around the goal would be to pull one of the original 3 and replace with a drive at least the size of the first expansion but pref a bit bigger whilst watching the TB/£ and the next amount of dead space (if any).

Rinse and repeat.

Oh and don't forget to backup your NAS, otherwise pain and misery awaits.

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[Telos]

If you can afford the “luxury” of keeping one bay empty, then you can use DSM's drive “replace” feature, which enables you to replace and existing drive, without going through the degrade/rebuild process.