advice on expanding RAID10 array

It only can be done online if the particular raid controller in the machine allows extension of a raid 10 online.

it would add another 146 GB brutto (you will have some less free due to filesystem overhead)

it would NOT risk to do this online, without a valid, recent and working backup.
Online rebuilding this array will put a lot of stress to all the disks, and there are 6 disks in each stripe set that are together, if one disk break in each stripe set your files will be lost.
Although the disks are small so a rebuild would not take too long.

no you cant add bigger disks to that RAID 10 to get more space. A raid 10 is a mirror of 2 or more raid 0. in raid 0 you only gat as much space as the smallest disk in the stipe set has.

so by adding 4 new 146 g disks what would my d volume be increased to?

ca. 820GB netto.

so I loose 3 disks and only gain 146gig space?

sorry you have 950 gb after adding 4 disks. Ive only calculated with 2 more.

would it be better to add larger disks under a new array

4 x 146gig disks and add them to the existing RAID 10 array
what you have now:
Capacity      876 GB
Speed gain      12x read and 6x write speed gain
Fault tolerance      At least 1-drive failure

What you will get:
Capacity      1168 GB
Speed gain      16x read and 8x write speed gain
Fault tolerance      At least 1-drive failure
Increase of 292GB
Raid Calculator

adding larger disks only if you can do it but remember you are limited to the smallest disk size. Since you can only tolerate a 1 drive failure backup/backup/backup did I say backup..

my d drive is only 684gig

oops I thought you had 12 disks and increasing to 16 for the raid 10.. recalculated RAW capacity before formatting and other disk overhead.. Don't forget that drive manufacturers use *1000 and operating systems use *1024 so a 146GB drive really is 136.6GB

Capacity      685 GB
Speed gain      10x read and 5x write speed gain
Fault tolerance      At least 1-drive failure

Capacity      959 GB
Speed gain      14x read and 7x write speed gain
Fault tolerance      At least 1-drive failure

959 - 685 = 274 increase with adding 4 disks

yes I have 12 disks in total 2 in RAID1 for OS
10 in RAID 10 for data
that's great many thanks
probably quite an expensive option just to get 274gig

ps
how do you know what to subtract for over head
ie
14 x 146 gig = 1022 gig
but you say only 959 will be available

perfect thank you

>is my only option to buy 4 x 146gig disks and add them to the existing RAID 10 array?

No it isn't your only option. You could convert the current RAID 10 to RAID 6 on the fly* without adding any disks, that would give you 3 * 146 GB extra space although the write speed would only be half as fast as it is currently due to the RAID 6 write performance penalty. (take it as 3*136GiB usable extra given the GB/GiB difference.)

You would still have 4 spare bays so you could add a hot spare or two in them if you want or indeed add another 4 * 146GB disks' worth of space and a little more speed to the new RAID 6. That would compensate a bit for the RAID 6 write penalty as you would be adding more disk spindles which adds more speed.

*online RAID level conversion takes a day or so, a week if you set the expansion priority low on a heavily used server. just maintain your current backup regime. You may need to buy a cache battery or FBWC module to enable it, I don't think you need an expensive license for RAID 6 any more.

thanks
its an oracle server so need the RAID 10 performance