hi there

im happy to report i have purchased a pro License, im quit happy with my unRAID server, interface, everything basically.

i have now 10TB running as parity, a bunch of HD & SSD as data disks (9 actually)

my use is very basic at the moment: serve audio & video files.

 

question is easy i hope:

1. would adding a SSD as cache improve write performance? if yes, what size would be ideal (array is now about 8.5 TB out of 13 TB available)

2. when i would write 2 files to cache, for example, are those writes then immediately secured by parity? if yes, then those writes would be as slow as writes to the array?

 

in long term i will have the whole array in SSD, but at the moment have 4 HDD in there

 

thank you in advance

BR

S

29 minutes ago, steven_76 said:

1. would adding a SSD as cache improve write performance? if yes, what size would be ideal (array is now about 8.5 TB out of 13 TB available)

Cache is generally set up to transfer files to the Array during a low usage period. The default value is around 3am I think.

To evaluate the size you would need, you should consider how much you tend to write to the Array each day.

29 minutes ago, steven_76 said:

2. when i would write 2 files to cache, for example, are those writes then immediately secured by parity? if yes, then those writes would be as slow as writes to the array?

The protection will depend on the number of devices in you cache. With a single device, there will not be any protection as you guessed. If you have more than one, then it will be set up to RAID1 by default. You can then change the default value to RAID0, 5,6,10, etc depending on your needs an the number of disks.

29 minutes ago, steven_76 said:

in long term i will have the whole array in SSD, but at the moment have 4 HDD in there

SSDs are not generally a good idea in the Array as TRIM is not available. However, since unRAID 6.9 (actually in beta) it is possible to have several disk Pools (for example, the Cache drive(s) are in a Pool.

And I forgot the first part of your question. Yes it should improve the write performance, but how much will depend of your system.

I max out my gigabit connection between my SSD in my computer and the Cache in my server. And if you have a network speed higher than 1 Gbps, the benefit would be higher.

If you are copying from an HDD to the server, the benefit might be less significant.

44 minutes ago, ChatNoir said:

Cache is generally set up to transfer files to the Array during a low usage period. The default value is around 3am I think.

To evaluate the size you would need, you should consider how much you tend to write to the Array each day.

The protection will depend on the number of devices in you cache. With a single device, there will not be any protection as you guessed. If you have more than one, then it will be set up to RAID1 by default. You can then change the default value to RAID0, 5,6,10, etc depending on your needs an the number of disks.

SSDs are not generally a good idea in the Array as TRIM is not available. However, since unRAID 6.9 (actually in beta) it is possible to have several disk Pools (for example, the Cache drive(s) are in a Pool.

thanks for your reply. the temporary vulnerability when writing to cache without priority is acceptable, i will only delete source files after files are visibibly transferred to the array

 

about TRIM, i check the discs before buying, and they explicitly state that they support TRIM (this is a garbage collection instruction if i understand correctly)

 

or is it unRAID that doesnt support TRIM? if it does not, i suppose it will be brought in the future. unRAID seems to be a healthy enterprise and will be aware of this TRIM situation

 

SSD are too tasty to pass up ))

37 minutes ago, ChatNoir said:

And I forgot the first part of your question. Yes it should improve the write performance, but how much will depend of your system.

I max out my gigabit connection between my SSD in my computer and the Cache in my server. And if you have a network speed higher than 1 Gbps, the benefit would be higher.

If you are copying from an HDD to the server, the benefit might be less significant.

im also on Gigabit switches, i max on 113MB, same. not sure if its realistic to buy 10Gb netwokr infra for all my machines, might be a nice project for the future

3 minutes ago, steven_76 said:

about TRIM, i check the discs before buying, and they explicitly state that they support TRIM (this is a garbage collection instruction if i understand correctly)

 

or is it unRAID that doesnt support TRIM? if it does not, i suppose it will be brought in the future. unRAID seems to be a healthy enterprise and will be aware of this TRIM situation

 

SSD are too tasty to pass up ))

I am not an expert on the details of this point. Maybe someone can chime in.

 

What I understand is that Unraid does support TRIM but not in the Array.

I would suppose that it is because of Parity. Moving data at the controller level without OS knowledge might invalidate parity ?

Trim is supported for any pool devices, currently not supported for array devices.

57 minutes ago, JorgeB said:

Trim is supported for any pool devices, currently not supported for array devices.

hi Jorge, and is this a future that we could expect in the middle-long future? im happy with unRAID in fact, its right on my level

i have currently 3 (soon 4) SSD devices in my array, works flawlessly , i may add

does this TRIM problem mean that , if i delete data on one of the SSD's, this space will not be recovered? (made available again)

BR

Steven

according to this here artical, TRIM is a nice-to-have , perfromance-wise and health-wise. but all basic functions will be there (ie garbage collection is not broken)

https://searchstorage.techtarget.com/definition/TRIM

10 minutes ago, steven_76 said:

and is this a future that we could expect in the middle-long future?

I would think (and hope) so.

 

11 minutes ago, steven_76 said:

if i delete data on one of the SSD's, this space will not be recovered?

No, it just means there could be some write performance deterioration with time, I have a small SSD array and for now it's performing normally even without trim.

excellent, thanks all of you. i implement my cache drive in the weekend (i love to work on my NAS to be honest.)

i have procured a second hand LSI MegaRAID SAS 9260-8i and some new breakout cables, ànd a recovery 256Gb SSD from work and a black friday score of 2TB SSD ))

so i wish you all a very nice weekend indeed

br

steven

 

PS can we post pictures somewhere of our build? i found these great 2.5" drive cages who take up one 5.25" slot, and they are in black mesh kinda, it fits the case perfectly, i think im in love )))

30 minutes ago, steven_76 said:

LSI MegaRAID SAS 9260-8i

This is not good for Unraid, look for a regular LSI HBA instead, not megaRAID models.

 

34 minutes ago, steven_76 said:

PS can we post pictures somewhere of our build?

Also have some 2.5" drive cages:

 

but for HDDs, the SSDs are in a controller like this one, only 4 data devices, like mentioned it's a small server (parity is NVMe).

 

 

 

 

Maybe I missed it, but I don't think anyone mentioned a possibly more important reason to not have SSDs in the parity array with HDDs.

 

No disk in the parity array can be written faster than parity.

Yep, I was talking about an SSD only array.

2 hours ago, trurl said:

Maybe I missed it, but I don't think anyone mentioned a possibly more important reason to not have SSDs in the parity array with HDDs.

 

No disk in the parity array can be written faster than parity.

that is an important little piece of info guys !!

ok so i should ask santa for a big ass SSD drive as parity, roger

that may be chrismtas 2023 ))

2 hours ago, JorgeB said:

 

 

Also have some 2.5" drive cages:

 

 

 

 

 

 

 

looking good , i like those status lights )) one can never have enough lights ))

On 11/26/2020 at 2:35 PM, JorgeB said:

This is not good for Unraid, look for a regular LSI HBA instead, not megaRAID models.

 

kind of selectively missed that

 

i have found a thread about re-flashing raid controllers, i will inform myself on that because i already have the card. i saw 9240-8i in the list of supported models and figured 9260-8i would be the same thing more or less

 

ah well, guess ill soon find out

10 minutes ago, steven_76 said:

would be the same thing more or less

It's not, although the 9240 is a megaraid model, it's a "lite" one, it uses the standard HBA chipset and can be flashed to IT mode, the 9260 can't.

3 hours ago, JorgeB said:

It's not, although the 9240 is a megaraid model, it's a "lite" one, it uses the standard HBA chipset and can be flashed to IT mode, the 9260 can't.

thats bad , thanks god i didnt pay a lot for. can keep it in the box then and offer straight back for sale ((

any hints to where i can score a card which offers 8 SATA connections for (very) good price in the EU ??

i usually buy in azerty.nl and alternate.be but there are not 8-port sata cards (and i needs to be max PCI 2.0 16x because MB)

finding a good card isnt easy, it appears (

 

got my self brandnew cables by card wont work now, ))

You can usually get an LSI HBA on ebay for 30€ or so, look for used server pulls.